Article Summary

Summary

Discusses how to create a custom Sling Servlet that uses the AEM QueryBuilder API to retrieve DAM assets. The Sling Servlet contains application logic that searches the AEM DAM for assets and places the collection of assets in a ZIP file. This article also discusses how to create a web page that invokes the Sling Servlet to download the ZIP file.

This article uses an Adobe Maven Archetype project to build an OSGi bundle that contains the Sling Servlet. If you are not familiar with an Adobe Maven Archetype project, it is recommended that you read the following article: Creating your first AEM Service using an Adobe Maven Archetype project.

This article uses of a ResourceResolverFactory to create a Session instance that is required to use the AEM Query Builder API. A Session instance is created by using the adaptTo method:

resourceResolver.adaptTo(Session.class);

Digital Marketing Solution(s) Adobe Experience Manager (Adobe CQ)
Audience
Developer (intermediate)
Required Skills
Java, Maven, HTML
Tested On Adobe Experience Manager 5.5, 5.6

Introduction

You can create an AEM Sling Servlet that uses the AEM Query Builder API to search the AEM Digital Asset Manager (DAM) and return a collection of assets within a ZIP file. The client web browser downloads the ZIP file that contains the DAM assets.

You can create a Sling Servlet that performs these tasks:

  • Uses the QueryBuilder API to search a specific DAM folder
  • Retrieves assets (for example, PNG files)
  • Places the assets in a ZIP file
  • Returns the ZIP file  

The following illustration shows the use case described in this development article. 

DAMAssets

In this development article, assume that the AEM DAM assets are located in the following DAM location: /content/dam/car.

DAMLocation

The query description is simply a set of predicates (Predicate). Examples include a full-text predicate, which corresponds to the jcr:contains() function in XPath, and an image size predicate that looks for width and height properties in the DAM asset subtree.

For each predicate type, there is an evaluator component (PredicateEvaluator) that knows how to handle that specific predicate for XPath, filtering, and facet extraction. It is very easy to create custom evaluators, which are plugged-in through the OSGi component runtime.

For more information about the Experience Manager Query Builder API, see Query Builder API.

This development article walks you through how to build an AEM Sling Servlet that uses the Query Builder API and searches the AEM DAM for digital assets. 

Note:

Instead of using the Query Builder API to search the AEM JCR, you can also use the JCR API. For details, see Querying Adobe Experience Manager Data using the JCR API.

Create an AEM application folder structure 

Create an AEM application folder structure that contains templates, components, and pages by using CRXDE Lite. 

CQAppSetup

The following describes each application folder:

  • application name: contains all of the resources that an application uses. The resources can be templates, pages, components, and so on.
  • components: contains components that your application uses. 
  • page: contains page components. A page component is a script such as a JSP file. 
  • global: contains global components that your application uses.
  • template: contains templates on which you base page components. 
  • src: contains source code that comprises an OSGi component (this development article does not create an OSGi bundle using this folder). 
  • install: contains a compiled OSGi bundles container.

To create an AEM application folder structure:

  1. To view the CQ welcome page, enter the URL http://[host name]:[port] into a web browser. For example, http://localhost:4502.
  2. Select CRXDE Lite (if you are using AEM 5.6, click Tools from the left menu). 
  3. Right-click the apps folder (or the parent folder), select Create, Create Folder.
  4. Enter the folder name into the Create Folder dialog box. Enter download
  5. Repeat steps 1-4 for each folder specified in the previous illustration. 
  6. Click the Save All button.

Note:

You have to click the Save All button when working in CRXDE Lite for the changes to be made. 

Create a template 

You can create a template by using CRXDE Lite. A CQ template enables you to define a consistent style for the pages in your application. A template comprises of nodes that specify the page structure. For more information about templates, see Templates.

To create a template, perform these tasks:
1. To view the CQ welcome page, enter the URL http://[host name]:[port] into a web browser. For example, http://localhost:4502.
2. Select CRXDE Lite (if you are using AEM 5.6, click Tools from the left menu).
3. Right-click the template folder (within your application), select Create, Create
Template.
4. Enter the following information into the Create Template dialog box:

  • Label: The name of the template to create. Enter downloadTemplate
  • Title: The title that is assigned to the template.
  • Description: The description that is assigned to the template.
  • Resource Type: The component's path that is assigned to the template and copied to implementing pages. Enter download/components/page/downloadTemplate.
  • Ranking: The order (ascending) in which this template will appear in relation to other templates. Setting this value to 1 ensures that the template appears first in the list.

5. Add a path to Allowed Paths. Click on the plus sign and enter the following value: /content(/.*)?.
6. Click Next for Allowed Parents.
7. Select OK on Allowed Children.
 

Create a render component that uses the template 

Components are re-usable modules that implement specific application logic to render the content of your web site. You can think of a component as a collection of scripts (for example, JSPs, Java servlets, and so on) that completely realize a specific function. In order to realize this functionality, it is your responsibility as a CQ developer to create scripts that perform specific functionality. For more information about components, see Components.

By default, a component has at least one default script, identical to the name of the component. To create a render component, perform these tasks:

1. To view the CQ welcome page, enter the URL http://[host name]:[port] into a web browser. For example, http://localhost:4502.
2. Select CRXDE Lite (if you are using AEM 5.6, click Tools from the left menu).
3. Right-click /apps/download/components/page, then select
Create, Create Component.
4. Enter the following information into the Create Component dialog box:

  • Label: The name of the component to create. Enter downloadTemplate. 
  • Title: The title that is assigned to the component.
  • Description: The description that is assigned to the template.

5. Select Next for Advanced Component Settings and Allowed Parents.
6. Select OK on Allowed Children.
7. Open the downloadTemplate.jsp located at: /apps/download/components/page/downloadTemplate/downloadTemplate.jsp.
8. Enter the following JSP code.
 

<html>
<head>
<title>Hello World !!!</title>
</head>
<body>
<h1>Hello Query Builder API!!!</h1>
<h2>This page will query the AEM JCR using the Query Builder API</h2>
</body>
</html>

Setup Maven

You can use Maven to build an OSGi bundle that uses the QueryBuilder API and is deployed. Maven manages required JAR files that a Java project needs in its class path. Instead of searching the Internet trying to find and download third-party JAR files to include in your project’s class path, Maven manages these dependencies for you.

You can download Maven 3 from the following URL:

http://maven.apache.org/download.html

After you download and extract Maven, create an environment variable named M3_HOME. Assign the Maven install location to this environment variable. For example:

C:\Programs\Apache\apache-maven-3.0.4

Set up a system environment variable to reference Maven. To test whether you properly setup Maven, enter the following Maven command into a command prompt:

%M3_HOME%\bin\mvn -version

This command provides Maven and Java install details and resembles the following message:

OS name: "windows 7", version: "6.1", arch: "amd64", family: "windows"
 

Note:

For more information about setting up Maven and the Home variable, see: Maven in 5 Minutes.

Next, copy the Maven configuration file named settings.xml from [install location]\apache-maven-3.0.4\conf\ to your user profile. For example, C:\Users\scottm\.m2\.

You have to configure your settings.xml file to use Adobe’s public repository. For information, see Adobe Public Maven Repository at http://repo.adobe.com/.

The following XML code represents a settings.xml file that you can use.

<?xml version="1.0" encoding="UTF-8"?>

<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->

<!--
 | This is the configuration file for Maven. It can be specified at two levels:
 |
 |  1. User Level. This settings.xml file provides configuration for a single user, 
 |                 and is normally provided in ${user.home}/.m2/settings.xml.
 |
 |                 NOTE: This location can be overridden with the CLI option:
 |
 |                 -s /path/to/user/settings.xml
 |
 |  2. Global Level. This settings.xml file provides configuration for all Maven
 |                 users on a machine (assuming they're all using the same Maven
 |                 installation). It's normally provided in 
 |                 ${maven.home}/conf/settings.xml.
 |
 |                 NOTE: This location can be overridden with the CLI option:
 |
 |                 -gs /path/to/global/settings.xml
 |
 | The sections in this sample file are intended to give you a running start at
 | getting the most out of your Maven installation. Where appropriate, the default
 | values (values used when the setting is not specified) are provided.
 |
 |-->
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0" 
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  <!-- localRepository
   | The path to the local repository maven will use to store artifacts.
   |
   | Default: ~/.m2/repository
  <localRepository>/path/to/local/repo</localRepository>
  -->

  <!-- interactiveMode
   | This will determine whether maven prompts you when it needs input. If set to false,
   | maven will use a sensible default value, perhaps based on some other setting, for
   | the parameter in question.
   |
   | Default: true
  <interactiveMode>true</interactiveMode>
  -->

  <!-- offline
   | Determines whether maven should attempt to connect to the network when executing a build.
   | This will have an effect on artifact downloads, artifact deployment, and others.
   |
   | Default: false
  <offline>false</offline>
  -->

  <!-- pluginGroups
   | This is a list of additional group identifiers that will be searched when resolving plugins by their prefix, i.e.
   | when invoking a command line like "mvn prefix:goal". Maven will automatically add the group identifiers
   | "org.apache.maven.plugins" and "org.codehaus.mojo" if these are not already contained in the list.
   |-->
  <pluginGroups>
    <!-- pluginGroup
     | Specifies a further group identifier to use for plugin lookup.
    <pluginGroup>com.your.plugins</pluginGroup>
    -->
  </pluginGroups>

  <!-- proxies
   | This is a list of proxies which can be used on this machine to connect to the network.
   | Unless otherwise specified (by system property or command-line switch), the first proxy
   | specification in this list marked as active will be used.
   |-->
  <proxies>
    <!-- proxy
     | Specification for one proxy, to be used in connecting to the network.
     |
    <proxy>
      <id>optional</id>
      <active>true</active>
      <protocol>http</protocol>
      <username>proxyuser</username>
      <password>proxypass</password>
      <host>proxy.host.net</host>
      <port>80</port>
      <nonProxyHosts>local.net|some.host.com</nonProxyHosts>
    </proxy>
    -->
  </proxies>

  <!-- servers
   | This is a list of authentication profiles, keyed by the server-id used within the system.
   | Authentication profiles can be used whenever maven must make a connection to a remote server.
   |-->
  <servers>
    <!-- server
     | Specifies the authentication information to use when connecting to a particular server, identified by
     | a unique name within the system (referred to by the 'id' attribute below).
     | 
     | NOTE: You should either specify username/password OR privateKey/passphrase, since these pairings are 
     |       used together.
     |
    <server>
      <id>deploymentRepo</id>
      <username>repouser</username>
      <password>repopwd</password>
    </server>
    -->
    
    <!-- Another sample, using keys to authenticate.
    <server>
      <id>siteServer</id>
      <privateKey>/path/to/private/key</privateKey>
      <passphrase>optional; leave empty if not used.</passphrase>
    </server>
    -->
  </servers>

  <!-- mirrors
   | This is a list of mirrors to be used in downloading artifacts from remote repositories.
   | 
   | It works like this: a POM may declare a repository to use in resolving certain artifacts.
   | However, this repository may have problems with heavy traffic at times, so people have mirrored
   | it to several places.
   |
   | That repository definition will have a unique id, so we can create a mirror reference for that
   | repository, to be used as an alternate download site. The mirror site will be the preferred 
   | server for that repository.
   |-->
  <mirrors>
    <!-- mirror
     | Specifies a repository mirror site to use instead of a given repository. The repository that
     | this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used
     | for inheritance and direct lookup purposes, and must be unique across the set of mirrors.
     |
    <mirror>
      <id>mirrorId</id>
      <mirrorOf>repositoryId</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://my.repository.com/repo/path</url>
    </mirror>
     -->
  </mirrors>
  
  <!-- profiles
   | This is a list of profiles which can be activated in a variety of ways, and which can modify
   | the build process. Profiles provided in the settings.xml are intended to provide local machine-
   | specific paths and repository locations which allow the build to work in the local environment.
   |
   | For example, if you have an integration testing plugin - like cactus - that needs to know where
   | your Tomcat instance is installed, you can provide a variable here such that the variable is 
   | dereferenced during the build process to configure the cactus plugin.
   |
   | As noted above, profiles can be activated in a variety of ways. One way - the activeProfiles
   | section of this document (settings.xml) - will be discussed later. Another way essentially
   | relies on the detection of a system property, either matching a particular value for the property,
   | or merely testing its existence. Profiles can also be activated by JDK version prefix, where a 
   | value of '1.4' might activate a profile when the build is executed on a JDK version of '1.4.2_07'.
   | Finally, the list of active profiles can be specified directly from the command line.
   |
   | NOTE: For profiles defined in the settings.xml, you are restricted to specifying only artifact
   |       repositories, plugin repositories, and free-form properties to be used as configuration
   |       variables for plugins in the POM.
   |
   |-->
  <profiles>
    <!-- profile
     | Specifies a set of introductions to the build process, to be activated using one or more of the
     | mechanisms described above. For inheritance purposes, and to activate profiles via <activatedProfiles/>
     | or the command line, profiles have to have an ID that is unique.
     |
     | An encouraged best practice for profile identification is to use a consistent naming convention
     | for profiles, such as 'env-dev', 'env-test', 'env-production', 'user-jdcasey', 'user-brett', etc.
     | This will make it more intuitive to understand what the set of introduced profiles is attempting
     | to accomplish, particularly when you only have a list of profile id's for debug.
     |
     | This profile example uses the JDK version to trigger activation, and provides a JDK-specific repo.
    <profile>
      <id>jdk-1.4</id>

      <activation>
        <jdk>1.4</jdk>
      </activation>

      <repositories>
        <repository>
          <id>jdk14</id>
          <name>Repository for JDK 1.4 builds</name>
          <url>http://www.myhost.com/maven/jdk14</url>
          <layout>default</layout>
          <snapshotPolicy>always</snapshotPolicy>
        </repository>
      </repositories>
    </profile>
    -->

    <!--
     | Here is another profile, activated by the system property 'target-env' with a value of 'dev',
     | which provides a specific path to the Tomcat instance. To use this, your plugin configuration
     | might hypothetically look like:
     |
     | ...
     | <plugin>
     |   <groupId>org.myco.myplugins</groupId>
     |   <artifactId>myplugin</artifactId>
     |   
     |   <configuration>
     |     <tomcatLocation>${tomcatPath}</tomcatLocation>
     |   </configuration>
     | </plugin>
     | ...
     |
     | NOTE: If you just wanted to inject this configuration whenever someone set 'target-env' to
     |       anything, you could just leave off the <value/> inside the activation-property.
     |
    <profile>
      <id>env-dev</id>

      <activation>
        <property>
          <name>target-env</name>
          <value>dev</value>
        </property>
      </activation>

      <properties>
        <tomcatPath>/path/to/tomcat/instance</tomcatPath>
      </properties>
    </profile>
    -->
  

<profile>

                <id>adobe-public</id>

                <activation>

                    <activeByDefault>true</activeByDefault>

                </activation>

                <repositories>

                  <repository>

                    <id>adobe</id>

                    <name>Nexus Proxy Repository</name>

                    <url>http://repo.adobe.com/nexus/content/groups/public/</url>

                    <layout>default</layout>

                  </repository>

                </repositories>

                <pluginRepositories>

                  <pluginRepository>

                    <id>adobe</id>

                    <name>Nexus Proxy Repository</name>

                    <url>http://repo.adobe.com/nexus/content/groups/public/</url>

                    <layout>default</layout>

                  </pluginRepository>

                </pluginRepositories>

            </profile>

</profiles>

  <!-- activeProfiles
   | List of profiles that are active for all builds.
   |
  <activeProfiles>
    <activeProfile>alwaysActiveProfile</activeProfile>
    <activeProfile>anotherAlwaysActiveProfile</activeProfile>
  </activeProfiles>
  -->
</settings>

Create an Experience Manager archetype project 

You can create an Experience Manager archetype project by using the Maven archetype plugin. In this example, assume that the working directory is C:\AdobeCQ.  

Maven

To create an archetype project, perform these steps::

1. Open the command prompt and go to your working directory (for example, C:\AdobeCQ).

2. Run the following Maven command:

mvn archetype:generate -DarchetypeRepository=https://repo.adobe.com/nexus/content/groups/public/ -DarchetypeGroupId=com.day.jcr.vault -DarchetypeArtifactId=multimodule-content-package-archetype -DarchetypeVersion=1.0.2 -DgroupId=com.adobe.cq.sling.download -DartifactId=download -Dversion=1.0-SNAPSHOT -Dpackage=com.adobe.cq.sling.download -DappsFolderName=myproject -DartifactName="My Project" -DcqVersion="5.6.1" -DpackageGroup="My Company"

3. When prompted for additional information, specify Y.

4. Once done, you will see a message like:
[INFO] Finished at: Wed Mar 27 13:38:58 EDT 2013
[INFO] Final Memory: 10M/184M

5. Change the command prompt to the generated project. For example: C:\AdobeCQ\download. Run the following Maven command:
mvn eclipse:eclipse

After you run this command, you can import the project into Eclipse as discussed in the next section.
 

Add Java files to the Maven project using Eclipse 

To make it easier to work with the Maven generated project, import it into the Eclipse development environment, as shown in the following illustration. 

project

The next step is to add Java file to the com.adobe.cq.sling.download package. The Java class, named DownloadAssets, that you create in this section extends the Sling class named org.apache.sling.api.servlets.SlingAllMethodsServlet. This class supports the doGet method that lets you sent a request to the servlet and get back a response (in this use case, the response is a ZIP file). For information about this class, see Class SlingAllMethodsServlet.

DownloadAssets class 

The DownloadAssets class uses the following Apache Felix SCR annotations:

  • @SlingServlet- defines the class as a Sling Servlet
  • @Reference - injects ResourceResolverFactory and QueryBuilder instances into the Sling Servlet

Note:

For information about Apache Felix SCR annotations, see http://felix.apache.org/documentation/subprojects/apache-felix-maven-scr-plugin/scr-annotations.html

In this development article, a QueryBuilder instance is injected into the doGet method. This instance is used to retrieve DAM Assets located in /content/dam/car.  

@Reference
	private QueryBuilder builder;

Note:

When working with the QueryBuilder API, it is strongly recommended that you use the QueryBuilder debugger tool. For more information, see How to Use CQ’s Query Debugger Tool

Within the doGet method, a ResourceResolverFactory instance is injected. This instance is required to create a Session instance that lets you create a Query instance. To inject a ResourceResolverFactory instance, you use the @Reference annotation to define a class member, as shown in the following example.

@Reference
private ResourceResolverFactory resolverFactory;

The goGet method creates a ZIP file (that contains the digital assets) and uses a ServletOutputStream instance to write out the ZIP file in the HTTP Response stream.

The Java class uses a SlingServlet annotation:

@SlingServlet(paths="/bin/myDownloadServlet", methods = "POST", metatype=true)

The paths property corresponds to the URL that you specify when using invoking the servlet. Later in this article, this is invoked using an href tag.

The following Java code represents the entire DownloadAssets class. 

package com.adobe.cq.sling.download;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedInputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.rmi.ServerException;
import java.util.Dictionary;
import java.util.HashMap;
import java.util.Map;
import java.io.*;
import java.util.ArrayList;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
import java.util.Iterator;
import javax.servlet.ServletOutputStream ; 

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
import org.apache.felix.scr.annotations.Properties;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.sling.SlingServlet;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.apache.sling.commons.osgi.OsgiUtil;
import org.apache.sling.jcr.api.SlingRepository;
import org.apache.felix.scr.annotations.Reference;
import org.osgi.service.component.ComponentContext;
import javax.jcr.Session;
import javax.jcr.Node; 
  
  
//Sling Imports
import org.apache.sling.api.resource.ResourceResolverFactory ; 
import org.apache.sling.api.resource.ResourceResolver; 
import org.apache.sling.api.resource.Resource; 
   
 
//QueryBuilder APIs
import com.day.cq.search.QueryBuilder; 
import com.day.cq.search.Query; 
import com.day.cq.search.PredicateGroup;
import com.day.cq.search.result.SearchResult;
import com.day.cq.search.result.Hit; 

//DAM API
import com.day.cq.dam.api.Asset ; 

@SlingServlet(paths="/bin/myDownloadServlet", methods = "GET", metatype=true)
public class DownloadAssets extends org.apache.sling.api.servlets.SlingAllMethodsServlet{
	
	
	//Set up References
	/** Default log. */
	protected final Logger log = LoggerFactory.getLogger(this.getClass());
	          
	private Session session;
	              
	//Inject a Sling ResourceResolverFactory
	@Reference
	private ResourceResolverFactory resolverFactory;
	          
	@Reference
	private QueryBuilder builder;
	
	
	@Override
	//The GET Method uses the AEM QueryBuilder API to retrieve DAM Assets, places them in a ZIP and returns it
	//in the HTTP output stream
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServerException, IOException {
      
     try
     {
    	//Invoke the adaptTo method to create a Session 
    	ResourceResolver resourceResolver = resolverFactory.getAdministrativeResourceResolver(null);
    	session = resourceResolver.adaptTo(Session.class);
         
    	// create query description as hash map (simplest way, same as form post)
        Map<String, String> map = new HashMap<String, String>();
     
        //set QueryBuilder search criteria                   
        map.put("type", "dam:Asset");
        map.put("path", "/content/dam/car"); 
        map.put("property.value", "image/png");
       
        builder= resourceResolver.adaptTo(QueryBuilder.class);
        
        //INvoke the Search query
        Query query = builder.createQuery(PredicateGroup.create(map), session);
        
        SearchResult sr= query.getResult();
        
        //write out to the AEM Log file
        log.info("Search Results: " +sr.getTotalMatches() ) ;
        
        //Create a MAP to store results
        Map<String, InputStream> dataMap = new HashMap<String, InputStream>();
    
        // iterating over the results
        for (Hit hit : sr.getHits()) {
            
        	//Convert the HIT to an asset - each asset will be placed into a ZIP for downloading
        	String path = hit.getPath();
        	Resource rs = resourceResolver.getResource(path);
            Asset asset = rs.adaptTo(Asset.class);   
              
            //We have the File Name and the inputstream
            InputStream data = asset.getOriginal().getStream();
            String name =asset.getName(); 
                        
           //Add to map
            dataMap.put(name, data); // key is fileName and value is inputStream - this will all be placed in ZIP file
       }
                   
        //ZIP up the AEM DAM Assets
        byte[] zip = zipFiles(dataMap);
        
        //
        // Sends the response back to the user / browser. The
        // content for zip file type is "application/zip". We
        // also set the content disposition as attachment for
        // the browser to show a dialog that will let user 
        // choose what action will he do to the sent content.
        //
        
        ServletOutputStream sos = response.getOutputStream();
        
        response.setContentType("application/zip");
        response.setHeader("Content-Disposition", "attachment;filename=dam.zip");
        
        
        // Write bytes to tmp file.
        sos.write(zip);
        sos.flush();    
        log.info("The ZIP is sent" ) ;    
     }
     catch(Exception e)
     {
    	 log.info("OH NO-- AN EXCEPTION: " +e.getMessage() );
     }
   }
	
	
	
	/**
     * Create the ZIP with AEM DAM Assets.
     */
    private byte[] zipFiles(Map data) throws IOException {
       
    	
    	
    	
    	ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ZipOutputStream zos = new ZipOutputStream(baos);
        byte bytes[] = new byte[2048];
    	Iterator<Map.Entry<String, InputStream>> entries = data.entrySet().iterator();
    	
    	while (entries.hasNext()) {
    	    Map.Entry<String, InputStream> entry = entries.next();
    	    
    	    String fileName =(String) entry.getKey(); 
    	    InputStream is1 =(InputStream) entry.getValue(); 
    	    
    	    BufferedInputStream bis = new BufferedInputStream(is1);

            //populate the next entry of the ZIP with the AEM DAM asset
            zos.putNextEntry(new ZipEntry(fileName));

            int bytesRead;
            while ((bytesRead = bis.read(bytes)) != -1) {
                zos.write(bytes, 0, bytesRead);
               
            }
            zos.closeEntry();
            bis.close();
            is1.close();
            
            
    	}
        
       zos.flush();
        baos.flush();
        zos.close();
        baos.close();

        return baos.toByteArray();
    }

}

Modify the Maven POM file 

Modify the POM files to successfully build the OSGi bundle. In the POM file located at C:\AdobeCQ\querybuilder\bundle, add the following dependencies. 

  • org.apache.felix.scr
  • org.apache.felix.scr.annotations
  • org.apache.jackrabbit
  • org.apache.sling
     

Because the QueryBuilder API is used, a Maven dependency on the repository that contains the QueryBuilder API exists. Add the following <repositories> element to your POM file.

<repositories>
    <repository>
        <id>adobe</id>
        <name>Adobe Public Repository</name>
        <url>http://repo.adobe.com/nexus/content/groups/public/</url>
        <layout>default</layout>
    </repository>
    </repositories>
        <pluginRepositories>
        <pluginRepository>
        <id>adobe</id>
        <name>Adobe Public Repository</name>
        <url>http://repo.adobe.com/nexus/content/groups/public/</url>
        <layout>default</layout>
    </pluginRepository>
</pluginRepositories>
 

Once you add this repository element to your POM file, you can add the following dependency to your POM file, that lets you use the QueryBuilder API in your Java code.

<dependency>
    <groupId>com.day.cq</groupId>
    <artifactId>cq-search</artifactId>
    <version>5.5.4</version>
    <scope>provided</scope>
</dependency>

The following XML represents the POM file to build the OSGi bundle that contains the QueryBuilder API.  

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd ">
    <modelVersion>4.0.0</modelVersion>
    <!-- ====================================================================== -->
    <!-- P A R E N T P R O J E C T D E S C R I P T I O N -->
    <!-- ====================================================================== -->
    <parent>
        <groupId>com.adobe.cq.sling.download</groupId>
        <artifactId>download</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <!-- ====================================================================== -->
    <!-- P R O J E C T D E S C R I P T I O N -->
    <!-- ====================================================================== -->

    <artifactId>download-bundle</artifactId>
    <packaging>bundle</packaging>
    <name>My Project Bundle</name>

  <dependencies>
        <dependency>
            <groupId>org.osgi</groupId>
            <artifactId>org.osgi.compendium</artifactId>
        </dependency>
        <dependency>
            <groupId>org.osgi</groupId>
            <artifactId>org.osgi.core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.apache.felix.scr.annotations</artifactId>
        </dependency>
    
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
    
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
           
      <dependency>
         <groupId>org.apache.felix</groupId>
         <artifactId>org.osgi.core</artifactId>
        <version>1.4.0</version>
      </dependency>
        
    <dependency>
        <groupId>org.apache.sling</groupId>
        <artifactId>org.apache.sling.commons.osgi</artifactId>
        <version>2.2.0</version>
    </dependency>
               
         
           
    <dependency>
    <groupId>org.apache.jackrabbit</groupId>
    <artifactId>jackrabbit-core</artifactId>
    <version>2.4.3</version>
    </dependency>
        
    <dependency>
    <groupId>org.apache.jackrabbit</groupId>
    <artifactId>jackrabbit-jcr-commons</artifactId>
    <version>2.4.3</version>
    </dependency>
    
    <dependency>
        <groupId>org.apache.sling</groupId>
        <artifactId>org.apache.sling.jcr.api</artifactId>
        <version>2.0.4</version>
      </dependency>
      
       <dependency>
            <groupId>org.apache.sling</groupId>
            <artifactId>org.apache.sling.api</artifactId>
            <version>2.2.4</version>
            <scope>provided</scope>
        </dependency>
 
       <dependency>
        <groupId>org.apache.sling</groupId>
        <artifactId>org.apache.sling.api</artifactId>
        <version>2.0.2-incubator</version>
      </dependency>    
          
      <dependency>
         <groupId>javax.jcr</groupId>
         <artifactId>jcr</artifactId>
         <version>2.0</version>
      </dependency>
 
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
</dependency>
             
    <dependency>
            <groupId>com.day.cq</groupId>
            <artifactId>cq-search</artifactId>
            <version>5.5.4</version>
            <scope>provided</scope>
        </dependency>
     
     
     
     
     <dependency>
            <groupId>com.day.cq</groupId>
            <artifactId>cq-search</artifactId>
            <version>5.5.4</version>
            <scope>provided</scope>
        </dependency>
         
         
         
        <dependency>
            <groupId>org.osgi</groupId>
            <artifactId>org.osgi.compendium</artifactId>
        </dependency>
        <dependency>
            <groupId>org.osgi</groupId>
            <artifactId>org.osgi.core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.apache.felix.scr.annotations</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
          
        <dependency>
         <groupId>org.apache.felix</groupId>
   
         <artifactId>org.osgi.core</artifactId>
   
         <version>1.4.0</version>
      </dependency>
         
         <dependency>
            <groupId>org.apache.sling</groupId>
            <artifactId>org.apache.sling.api</artifactId>
            <version>2.2.4</version>
            <scope>provided</scope>
        </dependency>
          
    <dependency>
    <groupId>org.apache.jackrabbit</groupId>
    <artifactId>jackrabbit-core</artifactId>
    <version>2.4.3</version>
    </dependency>
       
    <dependency>
    <groupId>org.apache.jackrabbit</groupId>
    <artifactId>jackrabbit-jcr-commons</artifactId>
    <version>2.4.3</version>
    </dependency>
   
    <dependency>
        <groupId>org.apache.sling</groupId>
        <artifactId>org.apache.sling.jcr.api</artifactId>
        <version>2.0.4</version>
      </dependency>
         
      <dependency>
         <groupId>javax.jcr</groupId>
         <artifactId>jcr</artifactId>
         <version>2.0</version>
      </dependency>
      
       <dependency>
            <groupId>com.day.cq.dam</groupId>
            <artifactId>cq-dam-api</artifactId>
            <version>5.5.0</version>
            <scope>provided</scope>
        </dependency>    
               
    </dependencies>

    <!-- ====================================================================== -->
    <!-- B U I L D D E F I N I T I O N -->
    <!-- ====================================================================== -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-scr-plugin</artifactId>
                <executions>
                    <execution>
                        <id>generate-scr-descriptor</id>
                        <goals>
                            <goal>scr</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-bundle-plugin</artifactId>
                <extensions>true</extensions>
                <configuration>
                    <instructions>
                        <Bundle-SymbolicName>com.adobe.cq.sling.download.download-bundle</Bundle-SymbolicName>
                    </instructions>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.sling</groupId>
                <artifactId>maven-sling-plugin</artifactId>
                <configuration>
                    <slingUrl>http://${crx.host}:${crx.port}/apps/myproject/install</slingUrl>
                    <usePut>true</usePut>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-javadoc-plugin</artifactId>
                 <configuration>
                    <excludePackageNames>
                        *.impl
                    </excludePackageNames>
                 </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Build the OSGi bundle using Maven 

To build the OSGi component by using Maven, perform these steps:

  1. Open the command prompt and go to the C:\AdobeCQ\download folder.
  2. Run the following maven command: mvn clean install.
  3. The OSGi component can be found in the following folder: C:\AdobeCQ\download\bundle\target. The file name of the OSGi component is download-bundle-1.0-SNAPSHOT.jar.

 

Deploy the bundle to Experience Manager

Once you deploy the OSGi bundle, you are able to invoke the doGet method defined in the DownloadAssets class (this is shown later in this development article). After you deploy the OSGi bundle, you will be able to see it in the Apache Felix Web Conole.

OSGiDownLoad

Deploy the OSGi bundle by performing these steps:

  1. Login to Apache Felix Web Console at http://server:port/system/console/bundles (default admin user = admin with password= admin).
  2. Click the Bundles tab, sort the bundle list by Id, and note the Id of the last bundle.
  3. Click the Install/Update button.
  4. Browse to the bundle JAR file you just built using Maven. (C:\AdobeCQ\download\bundle\target).
  5. Click Install.
  6. Click the Refresh Packages button.
  7. Check the bundle with the highest Id.
  8. Click Active. Your new bundle should now be listed with the status Active.
    If the status is not Active, check the CQ error.log for exceptions.

Modify the render component to invoke SearchService operations  

To create the AEM client that invokes the Sling Servlet and downloads the ZIP file, modify the downloadTemplate JSP file. The doGet method is invoked by using an a href tag.

<a href="/bin/myDownloadServlet" style="font-size: 30px; text-decoration: none">Download AEM DAM Assets</a>

Notice in the a href tag, the URL to the sling servlet is specified. This maps to the path property specified in the SlingServlet annotation

Add the following code to this file located at /apps/download/components/page/downloadTemplate/downloadTemplate.jsp.  

<%@include file="/libs/foundation/global.jsp"%>
<html>
<head>
<meta charset="UTF-8">
<title>Adobe AEM DAM Download Page</title>

</head>
    
<title>Sling Mobile Page</title>
    
<body>
  
           
<h1>Adobe Experience Manager DAM Download Example</h1>
          
<a href="/bin/myDownloadServlet" style="font-size: 30px; text-decoration: none">Download AEM DAM Assets</a>
        
 
  
</body>
  
</html>

Modify the downloadTemplate file:

  1. To view the CQ welcome page, enter the URL: http://[host name]:[port] into a web browser. For example, http://localhost:4502.
  2. Select CRXDE Lite. (If you are using AEM 5.6, click Tool in the left menu)
  3. Double-click apps/download/components/page/downloadTemplate/downloadTemplate.jsp.
  4. Replace the JSP code with the new code shown in this section.
  5. Click Save All.

 

Create an AEM web page that downloads DAM assets

The final task is to create a site that contains a page that is based on the downloadTemplate (the template created earlier in this development article). When the user clicks the download link, a ZIP file is downloaded, as shown here.

downloadClient

Create an AEM web page that downloads AEM DAM assets:

  1. Go to the Websites page at http://localhost:4502/siteadmin#/content.
  2. Select New Page.
  3. Specify the title of the page in the Title field.
  4. Specify the name of the page in the Name field.
  5. Select downloadTemplate from the template list that appears. This value represents the template that is created in this development article. If you do not see it, then repeat the steps in this development article. For example, if you made a typing mistake when entering in path information, the template will not show up in the New Page dialog box.
  6. Open the new page that you created by double-clicking it in the right pane. The new page opens in a web browser. You should see a page similar to the previous illustration.

See also

Congratulations, you have just created an AEM application that uses a custom Sling Servlet to download DAM Assets. Please refer to the AEM community page for other articles that discuss how to build AEM services/applications.

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