XULRunner with Java: JavaXPCOM Tutorial 1

这篇教程更新于2008年夏天,用来集成SWT和XULRunner来在SWT里显示一个浏览器。要想获得更多信息,请参考
http://www.eclipse.org/swt/faq.php#whatisbrowser

1,简介
       这篇教程有两个目的。首先,我们能学到一些XPCOM的概念和怎么通过JavaXPCOM来在java里使用它。其次,我们学到怎么在

java程序里嵌入Firefox浏览器。
       这里的例子我们开发,编译和测试的环境是Ubuntu 8.04和JDK1.6(译注,我使用的是windows xp)。我们在windows下遇到

一个问题,用户无法在form里输入文本,虽然在例子里并不需要这点。
1.1 下载资源  
      例子的源码在相关章节的开始以及文章的最后都有下载,当然,你也可以下载所有的代码
http://ladyr.es/wiki/attachment/wiki/XPCOMGuide/complete-guide-resources-windows.zip  windows
http://ladyr.es/wiki/attachment/wiki/XPCOMGuide/complete-guide-resources-linux.zip   linux

2. 安装XULRunner
     JavaXPCOM是一个用来访问XULRunner里XPCOM组件和服务的java库。在这里我们介绍了一些方法通过java来使用XULRunner组件

和服务。JavaXPCOM也能在java程序里嵌入Gecko。JavaXPCOM需要Java1.4.2或者更新的版本。为了使用JavaXPCOM你需要下面的步骤


    XULRunner:你需要安装XULRunner。它在开发中并不断变化。这个教程使用的是1.9的版本,这个版本built的时间是2008-6-19.

安装XULRunner的方法:
      1. 根据自己的操作系统下载合适的安装包(译注,我在windows xp下无法使用XULRunner1.9,我使用的是
                xulrunner-1.8.1.3.en-US.win32-20080128)
   2.解压它,比如把它解压到c:/XULRunner
   3.进入这个路径
   4.卸载以前的注册
   5.注册这个版本
   (译注:注册并不是必须的,注册后可以在程序里不用知道XULRunner的路径,不注册也可以,不过程序里要知道路径)
javaxpcom.jar
MozillaInterface.jar
MozillaGlue.jar

3.在Java里使用JavaXPCOM
3.1 JavaXPCOM初始化
XPCOM(Mozilla Cross-platform Object Model)是一个机遇组件的架构。为了使用XPCOM,我们需要一些初始化和清理的代码。有

两种方法来使用它,请看下面注释过的代码:
首先我们可以使用initXPCOM方法

    package es.ladyr.javaxpcom.test;  
    import java.io.File;  
    import java.io.FileNotFoundException;  
    import java.util.Properties;  
    import org.mozilla.xpcom.GREVersionRange;  
    import org.mozilla.xpcom.Mozilla;  
    public class SimplestInitializationCode {  
            public static void main(String[] args) {  
                    // JavaXPCOM initialization  
                    GREVersionRange[] range = new GREVersionRange[1];  
                    range[0] = new GREVersionRange("1.8", true, "1.9+", true);  
                    Properties props = null;  
                    File grePath = null;  
                    try {  
                            grePath = Mozilla.getGREPathWithProperties(range, props);  
                    } catch (FileNotFoundException e) {  
                            System.out.println("XULRunner not found. It is possible that it be wrong installed");  
                            return;  
                    }  
                     
                    Mozilla mozilla = Mozilla.getInstance();  
                    mozilla.initialize(grePath);  
                    try {  
                            mozilla.initXPCOM(grePath, null);  
                     
                    } catch (Throwable t) {  
                            System.out.println("initXPCOM failed");  
                            t.printStackTrace();  
                            return;  
                    }  
                    // From this line, we can use JavaXPCOM  
                    System.out.println("/n--> initialized/n");  
                     
                    // ... your application code ...  
                    // JavaXPOM finalization  
                    mozilla.shutdownXPCOM(null);  
            }  
    }  
 


为了嵌入,你应该使用 initEmbedding 方法。这个方法需要实现 IAppFileLocProvider 的类。我们使用包http://www.my400800.cn

    org.eclipse.atf.mozilla.ide.core里的一个类LocationProvider 。它的代码如下:  
    /******************************************************************* 
     * 
     * Licensed Materials - Property of IBM 
     * 
     * AJAX Toolkit Framework 6-28-496-8128 
     * 
     * (c) Copyright IBM Corp. 2006 All Rights Reserved. 
     * 
     * U.S. Government Users Restricted Rights - Use, duplication or 
     * disclosure restricted by GSA ADP Schedule Contract with IBM Corp. 
     * 
     *******************************************************************/  
    package org.eclipse.atf.mozilla.ide.core;  
    import java.io.File;  
    import java.io.FileNotFoundException;  
    import java.io.IOException;  
    import org.mozilla.xpcom.IAppFileLocProvider;  
    public class LocationProvider implements IAppFileLocProvider {  
            private File libXULPath;  
            private File profile;  
            private File history;  
             
            public LocationProvider(File aBinPath, File aProfileDir)  
            throws IOException {  
                    libXULPath = aBinPath;  
                    profile = aProfileDir;  
                    if (!libXULPath.exists() || !libXULPath.isDirectory()) {  
                            throw new FileNotFoundException("libxul directory specified is not valid: "  
                                            + libXULPath.getAbsolutePath());  
                    }  
                    if (profile != null && (!profile.exists() || !profile.isDirectory())) {  
                            throw new FileNotFoundException("profile directory specified is not valid: "  
                                            + profile.getAbsolutePath());  
                    }  
                    // create history file  
                    if (profile != null) {  
                            setupProfile();  
                    }  
            }  
             
            private void setupProfile() throws IOException {  
                    history = new File(profile, "history.dat");  
                    if (!history.exists()) {  
                            history.createNewFile();  
                    }  
            }  
            public File getFile(String aProp, boolean[] aPersistent) {  
                    File file = null;  
                    if (aProp.equals("GreD") || aProp.equals("GreComsD")) { //$NON-NLS-1$  
    //                      file = new File(grePath);  
                            file = libXULPath;  
                            if (aProp.equals("GreComsD")) { //$NON-NLS-1$  
                                    file = new File(file, "components"); //$NON-NLS-1$  
                            }  
                    }  
                    else if (aProp.equals("MozBinD") ||  //$NON-NLS-1$  
                            aProp.equals("CurProcD") || //$NON-NLS-1$  
                            aProp.equals("ComsD"))  //$NON-NLS-1$  
                    {  
                            file = libXULPath;  
                            if (aProp.equals("ComsD")) { //$NON-NLS-1$  
                                    file = new File(file, "components"); //$NON-NLS-1$  
                            }  
                    }  
                    else if (aProp.equals("ProfD")) {       //$NON-NLS-1$  
                            return profile;  
                    }  
                    else if (aProp.equals("UHist")) {       //$NON-NLS-1$  
                            return history;  
                    }  
    //              else {  
    //                      System.err.println("LocationProvider::getFile() => unhandled property = " + aProp);  
    //              }  
                    return file;  
            }  
            public File[] getFiles(String aProp) {  
                    File[] files = null;  
                    if (aProp.equals("APluginsDL")) { //$NON-NLS-1$  
                            files = new File[1];  
                            files[0] = new File(libXULPath, "plugins");  
    //              } else {  
    //                      System.err.println("LocationProvider::getFiles() => unhandled property = " + aProp);  
                    }  
                    return files;  
            }  
    }  
 



关于更多ATF的信息,请访问http://www.eclipse.org/atf/
 
为了嵌入而初始JavaXPCOM的代码如下:

    package es.ladyr.javaxpcom.test;  
    import java.io.File;  
    import java.io.FileNotFoundException;  
    import java.io.IOException;  
    import java.util.Properties;  
    import org.eclipse.atf.mozilla.ide.core.LocationProvider;  
    import org.mozilla.xpcom.GREVersionRange;  
    import org.mozilla.xpcom.Mozilla;  
    import org.mozilla.xpcom.XPCOMException;  
    public class EmbeddingInitializationCode {  
            public static void main(String[] args) {  
                    // JavaXPCOM initialization  
                    GREVersionRange[] range = new GREVersionRange[1];  
                    range[0] = new GREVersionRange("1.8", true, "1.9+", true);  
                    Properties props = null;  
                    File grePath = null;  
                    try {  
                            grePath = Mozilla.getGREPathWithProperties (range, props);  
                    } catch (FileNotFoundException e) {  
                            System.out.println("XULRunner not found. It is possible that it be wrong installed");  
                            return;  
                    }  
                    Mozilla mozilla = Mozilla.getInstance();  
                    mozilla.initialize(grePath);  
                    LocationProvider locProvider;  
                    try {  
                            locProvider = new LocationProvider(grePath, grePath);  
                    } catch (IOException e) {  
                            System.out.println("XULRunner not found. It is possible that it be wrong installed");  
                            return;  
                    }         
                    mozilla.initEmbedding(grePath, grePath, locProvider);  
                    // From this line, we can use JavaXPCOM  
                    System.out.println("/n--> initialized/n");  
                     
                    // ... your application code ...  
                    // JavaXPOM finalization  
                    try {  
                            mozilla.termEmbedding();  
                    } catch (XPCOMException e) {  
                            // this exception is thrown if termEmbedding failed  
                    }  
            }  
    }  
 



3.2 XPCOM组件和接口的基本概念
   XPCOM(Mozilla Cross-platform Object Model)如它名字,是一个基于组件的架构。XPCOM的组件一般是本地实现的。XPCOM系统

里的所有组件都有一个唯一的标识。XPCOM组件实现许多接口,这些接口提供各种功能。同一个组件可能实现不同的接口,同样,一

个接口可能北不同的组件实现。因为接口必需有一个具体的实现才能使用,我们将讨论组件和接口。在后面,我们把组件看成一段实

现了一个或多个接口的代码。
   在XULRunner里,接口名总是以nsI开头。在JavaXPCOM里,每个XPCOM接口都有一个对应的java接口。它们的名字以nsI开头,它们

位于org.mozilla.xpcom里,被放在MozillaInterfaces.jar包里面。这些接口的javaDoc在MozillaInterfaces-src.jar里。你可以在

https://developer.mozilla.org/En浏览所有的XPCOM接口,MDC是一个与语言无关的文档,并不是Java的。
   在JavaXPCOM里没有XPCOM组件的代码。后面你将看到怎么在JavaXPCOM里初始化和使用组件。因为没有java代码,所有也没有

JavaDoc。http://developer.mozilla.org/En里包含了XPCOM组件的完整文档。
   我们可以如下的步骤使用XPCOM组件:
      得到组件
      得到实现了我们想使用的接口的组件
      调用它
   组件使用URI来命名,例如,@mozilla.org/file/local;1。Mozilla的组件以@mozilla.org开头。这个URI是contractID,每个组

件也有一个组件标识符(CID)。同样,每一个接口也有一个接口标识符(IID)。IID总能使用一个static的final的属性来获取。组件可

能存在一个对象实例或者单例的服务。通常,服务包含单词Service或者Manager

3.3 使用JavaXPCOM: 与用JavaScript来使用XPCOM的不同点与相同点
   在XPCOM里,所有的接口都继承了nsISupports,它有一个函数叫做QueryInterface,这个函数返回一个组件的一个接口,如果这

个组件没有实现这个接口,那么将返回异常。在JavaXPCOM里,接口nsISupports提供了QueryInterface来返回一个nsISupports对象
。为了属于谋个接口的方法,你首先需要使用QueryInterface方法确定这个接口。

   比如,你可以使用下面的JavaScript来调用XPCOM来创建一个本地文件组件:
// Get the component
var aFile = Components.classes["@mozilla.org/file/local;1"].createInstance();

// Get the part of the component corresponding to the interface that we want to use
var aLocalFile = aFile.QueryInterface(Components.interfaces.nsILocalFile);

// Call the function (one or more than one)
aLocalFile.initWithPath("/mozilla/testfile.txt");


上面需要两行JavaScript代码来创建组件和获得接口。可以简化的代码:
// Get the component and directly the part of the component corresponding to the interface that we want to use
var aLocalFile = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile);

// Call the function (one or more than one)
aLocalFile.initWithPath("/mozilla/testfile.txt");

在JavaXPCOM里,为了得到XPCOM组件相对应的JavaXPCOM的实例,我们必须访问ComponentManager对象,这个对象允许在运行时访问

和使用。它能够通过单例类Mozilla的getComponentManager()访问。每次我们用这种方法实例化,我们创建了一个XPCOM组件。有两

种方法来创建XPCOM组件的实例:
   使用组件ID(CID):
// Get the component manager
ComponentManager cm = Mozilla.getInstance().getComponentManager();

// Get the part of the component corresponding to the interface that we want to use
nsISupports obj = cm.createInstance("{6ddb050c-0d04-11d4-986e-00c04fa0cf4a}", null, nsISupports.NS_ISUPPORTS_IID);

// Get the part of the component corresponding to the interface that we want to use
nsIInputStreamChannel isc = obj.queryInterface(nsIInputStreamChannel.NS_IINPUTSTREAMCHANNEL_IID);

// Call the method (one or more than one)
System.out.println("Content-Length: " + isc.getContentLength());

我们可以简化一下:
// Get the component manager
ComponentManager cm = Mozilla.getInstance().getComponentManager();

// Get the part of the component corresponding to the interface that we want to use
nsIInputStreamChannel isc = (nsIInputStreamChannel)
         cm.createInstance("{6ddb050c-0d04-11d4-986e-00c04fa0cf4a}", null,

nsIInputStreamChannel.NS_IINPUTSTREAMCHANNEL_IID);

// Call the method (one or more than one)
System.out.println("Content-Length: " + isc.getContentLength());

也可以通过contractID来访问:
// Get the component manager
ComponentManager cm = Mozilla.getInstance().getComponentManager();

// Get the part of the component corresponding to the interface that we want to use
nsISupports obj = cm.createInstanceByContractID("@ mozilla.org/file/local;1", null, nsISupports.NS_ISUPPORTS_IID);

// Get the part of the component corresponding to the interface that we want to use
nsILocalFile file = obj.queryInterface(nsILocalFile.NS_ILOCALFILE_IID);

// Call the method (one or more than one)
file.initWithPath("/home/alpgarcia/xpcom-file-test.txt");

简化形式:
// Get the component manager
ComponentManager cm = Mozilla.getInstance().getComponentManager();

// Get the part of the component corresponding to the interface that we want to use
nsILocalFile file = (nsILocalFile)cm.createInstanceByContractID("@ mozilla.org/file/local;1", null,

nsILocalFile.NS_ILOCALFILE_IID);

// Call the method (one or more than one)
file.initWithPath("/home/alpgarcia/xpcom-file-test.txt");

在JavaScript里,我们通过调用instanceOf来检查一个组件是否实现了一个接口:

var aFile = Components.classes["@mozilla.org/file/local;1"].createInstance();
if (aFile instanceOf Components.interfaces.nsILocalFile){
   var aLocalFile = aFile.QueryInterface(Components.interfaces.nsILocalFile);
   ...
}


在java里,instanceof运算符是其它的含义。在java里只能通过QueryInterface来判断。如果调用失败,那么这个组件就没有实现特

定的接口。如果我们还是用JavaScript的写法,那么就会得到不同的结果(错误的)。试试下面的代码:

 

    package es.ladyr.javaxpcom.test;  
      
    import java.io.File;  
    import java.io.FileNotFoundException;  
    import java.util.Properties;  
    import org.mozilla.xpcom.GREVersionRange;  
    import org.mozilla.xpcom.Mozilla;  
    import org.mozilla.xpcom.XPCOMException;  
    import org.mozilla.interfaces.nsIComponentManager;  
    import org.mozilla.interfaces.nsILocalFile;  
    import org.mozilla.interfaces.nsIMutableArray;  
    import org.mozilla.interfaces.nsISupports;  
    public class InstanceOfTest {  
            public static void main(String[] args) {  
                    // JavaXPCOM initialization  
                    GREVersionRange[] range = new GREVersionRange[1];  
                    range[0] = new GREVersionRange("1.8", true, "1.9+", true);  
                    Properties props = null;  
                    File grePath = null;  
                    try {  
                            grePath = Mozilla.getGREPathWithProperties(range, props);  
                    } catch (FileNotFoundException e) {  
                            System.out  
                                    .println("XULRunner not found. It is possible that it be wrong installed");  
                            return;  
                    }  
                    Mozilla mozilla = Mozilla.getInstance();  
                    mozilla.initialize(grePath);  
                    try {  
                            mozilla.initXPCOM(grePath, null);  
                    } catch (Throwable t) {  
                            System.out.println("initXPCOM failed");  
                            t.printStackTrace();  
                            return;  
                    }  
                    // From this line, we can use JavaXPCOM  
                    // Get the component manager  
                    nsIComponentManager cm = Mozilla.getInstance().getComponentManager();  
                    // We will not be able to know if that component implements a given  
                    // interface using instanceof in Java  
                    nsISupports aFile = cm  
                                    .createInstanceByContractID("@mozilla.org/file/local;1", null,  
                                                    nsISupports.NS_ISUPPORTS_IID);  
                    if (aFile instanceof nsILocalFile) {  
                            // The execution flow never come this way because instanceof  
                            // semantics are diferent in JavaScript and Java  
                            // (nsILocalFile is a chid class of nsISupports and not  
                            // the other way round)  
                            nsILocalFile aLocalFile = (nsILocalFile) aFile  
                                            .queryInterface(nsILocalFile.NS_ILOCALFILE_IID);  
                            System.out.println("This message will never be printed.");  
                    }  
                    try {  
                            nsILocalFile aLocalFile = (nsILocalFile) aFile  
                                            .queryInterface(nsILocalFile.NS_ILOCALFILE_IID);  
                            // The next sentences are executed if aFile component implements  
                            // nsILocalFile interface  
                            System.out  
                                            .println("nsILocalFile interface implemented by this component.");  
                            // Try to get an exception caused by a non implemented interface  
                            nsIMutableArray arr = (nsIMutableArray) aFile  
                                            .queryInterface(nsIMutableArray.NS_IMUTABLEARRAY_IID);  
                            System.out.println("This message will never be printed.");  
                    } catch (XPCOMException ex) {  
                            // The next sentences are executed if aFile component don't  
                            // implement nsILocalFile interface  
                            System.err  
                                            .println("Interface not supported. See the following exception: ");  
                            ex.printStackTrace();  
                            System.err.flush();  
                    }  
                    // The inverse case matchs with the semantics of Java instanceof  
                    // operator  
                    nsILocalFile aLocalFile = (nsILocalFile) aFile  
                                    .queryInterface(nsILocalFile.NS_ILOCALFILE_IID);  
                    if (aLocalFile instanceof nsISupports) {  
                            // The next sentence will be executed  
                            System.out.println("aLocalFile instance of nsISupports");  
                    }  
                    // JavaXPOM finalization  
                    mozilla.shutdownXPCOM(null);  
            }  
    }  
 



JavaScript和Java的主要区别是,在JavaXPCOM里没有一个特定的对象与XPCOM组件对应。
另外,我们可以使用另一类组件,叫做services。前面我们说过,Service作为一个单例存在,换句话说,你只能初始化一次。

Services被用来get和set全局的数据或者对其它对象进行操作。创建Service与创建组件类似,把getInstance()改成getService()就

行了。在JavaXPCOM里,我们需要nsIServiceManager对象来初始化一个Service。然后你需要调用getService或者

getServiceByContractID来得到service组件的引用。

在JavaScript里的代码:
// get the dns service component in JavaScript
var dnsservice = Components.classes["@mozilla.org/network/dns-service;1"].getService();
dnsservice.QueryInterface(Components.interfaces.nsIDNSService);

JavaXPCOM的代码:
//Now, we will try to use a service, for example, dns service
nsIServiceManager sm = mozilla.getServiceManager();
                               
nsIDNSService dns = (nsIDNSService) sm.getServiceByContractID(
        "@mozilla.org/network/dns-service;1", nsIDNSService.NS_IDNSSERVICE_IID);


3.4 在JavaXPCOM里使用组件和Services的完整例子
在第一个例子里我们将要创建一个本地的文件并写入一些文本。
package es.ladyr.javaxpcom.test;


 

    import java.io.File;  
    import java.io.FileNotFoundException;  
    import java.util.Properties;  
    import org.mozilla.xpcom.GREVersionRange;  
    import org.mozilla.xpcom.Mozilla;  
    import org.mozilla.interfaces.nsIComponentManager;  
    import org.mozilla.interfaces.nsIFileInputStream;  
    import org.mozilla.interfaces.nsIFileOutputStream;  
    //import org.mozilla.interfaces.nsILineInputStream;  
    import org.mozilla.interfaces.nsILocalFile;  
    import org.mozilla.interfaces.nsISeekableStream;  
    import org.mozilla.interfaces.nsISupports;  
      
    public class FileTest {  
            public static void main(String[] args) {  
                    // JavaXPCOM initialization  
                    GREVersionRange[] range = new GREVersionRange[1];  
                    range[0] = new GREVersionRange("1.8", true, "1.9+", true);  
                    Properties props = null;  
                    File grePath = null;  
                    try {  
                            grePath = Mozilla.getGREPathWithProperties(range, props);  
                    } catch (FileNotFoundException e) {  
                            System.out  
                                    .println("XULRunner not found. It is possible that it be wrong installed");  
                            return;  
                    }  
                    Mozilla mozilla = Mozilla.getInstance();  
                    mozilla.initialize(grePath);  
                    try {  
                            mozilla.initXPCOM(grePath, null);  
                    } catch (Throwable t) {  
                            System.out.println("initXPCOM failed");  
                            t.printStackTrace();  
                            return;  
                    }  
                    // From this line, we can use JavaXPCOM  
                    // First, we will create an empty file  
                    // A file is a component, we use the component manager to create an  
                    // instance  
                    // of local file component  
                    nsIComponentManager cm = mozilla.getComponentManager();  
                    // Here we create directly a component and use its nsILocalFile  
                    // interface  
                    nsILocalFile file = (nsILocalFile) cm.createInstanceByContractID(  
                                    "@mozilla.org/file/local;1", null,  
                                    nsILocalFile.NS_ILOCALFILE_IID);  
                    file.initWithPath("/home/sevi/xpcom-file-test.txt");  
                    // Check file existence because if the file already exists in filesystem  
                    // and  
                    // we try to create another one with the same path, an exception will be  
                    // thrown by XPCOM  
                    // (something like "The function "create" returned an error condition  
                    // (0x80520008)")  
                    if (!file.exists()) {  
                            file.create(nsILocalFile.NORMAL_FILE_TYPE, 0600);  
                    }  
                    // We can create a stream to write the file  
                    nsIFileOutputStream os = (nsIFileOutputStream) cm  
                                    .createInstanceByContractID(  
                                                    "@mozilla.org/network/file-output-stream;1", null,  
                                                    nsIFileOutputStream.NS_IFILEOUTPUTSTREAM_IID);  
                    os.init(file, nsISeekableStream.NS_SEEK_END, 0, 0);  
                    os.write("Hello World!/n", 13);  
                    os.flush();  
                    os.close();  
                    // And now we will use an input stream to read the file  
                    // The @mozilla.org/network/file-input-stream;1 component implements the  
                    // following interfaces:  
                    // * nsIFileInputStream  
                    // * nsIInputStream  
                    // * nsILineInputStream  
                    // * nsISeekableStream  
                    // * nsISupports  
                    // First create a parent component (top parent component). We could use  
                    // another component  
                    // implemented interface as well.  
                    nsISupports is = cm.createInstanceByContractID(  
                                    "@mozilla.org/network/file-input-stream;1", null,  
                                    nsISupports.NS_ISUPPORTS_IID);  
                    // We will use the file input stream interface to associate a local file  
                    // with the stream  
                    nsIFileInputStream fis = (nsIFileInputStream) is  
                                    .queryInterface(nsIFileInputStream.NS_IFILEINPUTSTREAM_IID);  
                    fis.init(file, nsIFileInputStream.REOPEN_ON_REWIND, 0, 0);  
                    System.out.println("The file contains " + fis.available()  
                                    + " bytes of data.");  
      
                    fis.close();  
                    // JavaXPOM finalization  
                    mozilla.shutdownXPCOM(null);  
                    System.out.println("Finish!");  
            }  
    }  
 




下面是一个关于域名的例子:

package es.ladyr.javaxpcom.test;  
import java.io.File;  
import java.io.FileNotFoundException;  
import java.util.Properties;  
import org.mozilla.xpcom.GREVersionRange;  
import org.mozilla.xpcom.Mozilla;  
import org.mozilla.interfaces.*;  
public class ServiceTest {  
        public static void main(String[] args) {  
                // JavaXPCOM initialization  
                GREVersionRange[] range = new GREVersionRange[1];  
                range[0] = new GREVersionRange("1.8", true, "1.9+", true);  
                Properties props = null;  
                File grePath = null;  
                try {  
                        grePath = Mozilla.getGREPathWithProperties(range, props);  
                } catch (FileNotFoundException e) {  
                        System.out  
                                        .println("XULRunner not found. It is possible that it be wrong installed");  
                        return;  
                }  
                Mozilla mozilla = Mozilla.getInstance();  
                mozilla.initialize(grePath);  
                 
                 
                try {  
                        mozilla.initXPCOM(grePath, null);  
                } catch (Throwable t) {  
                        System.out.println("initXPCOM failed");  
                        t.printStackTrace();  
                        return;  
                }  
                // From this line, we can use JavaXPCOM  
                // Now, we will try to use a service, for instance, dns service  
                nsIServiceManager sm = mozilla.getServiceManager();  
                nsIDNSService dns = (nsIDNSService) sm.getServiceByContractID(  
                                "@mozilla.org/network/dns-service;1",  
                                nsIDNSService.NS_IDNSSERVICE_IID);  
                System.out.println("Hostname: " + dns.getMyHostName());  
                nsIDNSRecord dnsRecord = dns.resolve("www.google.es",  
                                nsIDNSService.RESOLVE_CANONICAL_NAME  
                                                | nsIDNSService.RESOLVE_BYPASS_CACHE);  
                System.out.println("Canonical Name: " + dnsRecord.getCanonicalName()  
                                + " -- Next Address: " + dnsRecord.getNextAddrAsString());  
                // JavaXPOM finalization  
                mozilla.shutdownXPCOM(null);  
                System.out.println("Finish!");  
        }  
}  
 

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