Java 非常简单的代码不适用于HtmlUnit

我正在使用HtmlUnit 2.9（本月发布的稳定版本）。你知道为什么下面的代码不起作用吗

public class Main {

    public static void main(String[] args) {
        WebClient webClient = new WebClient(BrowserVersion.FIREFOX_3_6);
        webClient.setCssEnabled(true);
        webClient.setCssErrorHandler(new SilentCssErrorHandler());
        webClient.setThrowExceptionOnFailingStatusCode(false);
        webClient.setThrowExceptionOnScriptError(false);
        webClient.setRedirectEnabled(false);
        webClient.setAppletEnabled(false);
        webClient.setJavaScriptEnabled(false);
        webClient.setPopupBlockerEnabled(true);
        webClient.setTimeout(60000);
        webClient.setPrintContentOnFailingStatusCode(false);

        System.out.println("This is printed on screen");
        try {
            webClient.getPage("http://www.2cash.info/index.php");
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("This is NEVER printed on screen");
    }
}

我还添加了jstack的结果。注意，我标记了一个不断重复的部分：

2011-08-26 03:15:45
Full thread dump Java HotSpot(TM) Server VM (20.1-b02 mixed mode):

"Attach Listener" daemon prio=10 tid=0x09520400 nid=0x5363 waiting on condition [0x00000000]
   java.lang.Thread.State: RUNNABLE

"JS executor for com.gargoylesoftware.htmlunit.WebClient@a7c45e" daemon prio=10 tid=0x6feb7400 nid=0x5356 waiting on condition [0x6fcfe000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
    at java.lang.Thread.sleep(Native Method)
    at com.gargoylesoftware.htmlunit.javascript.background.JavaScriptExecutor.run(JavaScriptExecutor.java:166)
    at java.lang.Thread.run(Thread.java:662)

"Low Memory Detector" daemon prio=10 tid=0x70204c00 nid=0x5352 runnable [0x00000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=10 tid=0x70202800 nid=0x5351 runnable [0x00000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=10 tid=0x70200800 nid=0x5350 waiting on condition [0x00000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=10 tid=0x09514c00 nid=0x534f runnable [0x00000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=10 tid=0x09503400 nid=0x534e in Object.wait() [0x70798000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x76af2ff0> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118)
    - locked <0x76af2ff0> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134)
    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)

"Reference Handler" daemon prio=10 tid=0x09501c00 nid=0x534d in Object.wait() [0x707e9000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x7675cc58> (a java.lang.ref.Reference$Lock)
    at java.lang.Object.wait(Object.java:485)
    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
    - locked <0x7675cc58> (a java.lang.ref.Reference$Lock)

"main" prio=10 tid=0x09482400 nid=0x5349 runnable [0xb6c34000]
   java.lang.Thread.State: RUNNABLE
    at net.sourceforge.htmlunit.corejs.javascript.ScriptableObject.getSlot(ScriptableObject.java:2603)
    at net.sourceforge.htmlunit.corejs.javascript.ScriptableObject.defineProperty(ScriptableObject.java:1699)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.configureConstantsPropertiesAndFunctions(JavaScriptEngine.java:350)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.configureClass(JavaScriptEngine.java:330)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.init(JavaScriptEngine.java:199)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.access$000(JavaScriptEngine.java:79)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$1.run(JavaScriptEngine.java:146)
    at net.sourceforge.htmlunit.corejs.javascript.Context.call(Context.java:537)
    at net.sourceforge.htmlunit.corejs.javascript.ContextFactory.call(ContextFactory.java:538)
    at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.initialize(JavaScriptEngine.java:157)
    at com.gargoylesoftware.htmlunit.WebClient.initialize(WebClient.java:1141)
    at com.gargoylesoftware.htmlunit.WebWindowImpl.setEnclosedPage(WebWindowImpl.java:109)
    at com.gargoylesoftware.htmlunit.html.FrameWindow.setEnclosedPage(FrameWindow.java:102)
    at com.gargoylesoftware.htmlunit.html.HTMLParser.parse(HTMLParser.java:200)
    at com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml(HTMLParser.java:179)
    at com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage(DefaultPageCreator.java:221)
    at com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage(DefaultPageCreator.java:106)
    at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:433)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:311)
    at com.gargoylesoftware.htmlunit.html.BaseFrame.<init>(BaseFrame.java:73)
    at com.gargoylesoftware.htmlunit.html.HtmlInlineFrame.<init>(HtmlInlineFrame.java:46)
    at com.gargoylesoftware.htmlunit.html.DefaultElementFactory.createElementNS(DefaultElementFactory.java:288)
    at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.startElement(HTMLParser.java:506)
    at org.apache.xerces.parsers.AbstractSAXParser.startElement(Unknown Source)
    at org.cyberneko.html.HTMLTagBalancer.callStartElement(HTMLTagBalancer.java:1136)
    at org.cyberneko.html.HTMLTagBalancer.startElement(HTMLTagBalancer.java:742)
    at org.cyberneko.html.filters.DefaultFilter.startElement(DefaultFilter.java:136)
    at org.cyberneko.html.filters.NamespaceBinder.startElement(NamespaceBinder.java:278)
    at org.cyberneko.html.HTMLScanner$ContentScanner.scanStartElement(HTMLScanner.java:2652)
    at org.cyberneko.html.HTMLScanner$ContentScanner.scan(HTMLScanner.java:2022)
    at org.cyberneko.html.HTMLScanner.scanDocument(HTMLScanner.java:908)
    at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:499)
    at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:452)
    at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
    at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.parse(HTMLParser.java:789)
    at com.gargoylesoftware.htmlunit.html.HTMLParser.parse(HTMLParser.java:225)
    at com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml(HTMLParser.java:179)
    at com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage(DefaultPageCreator.java:221)
    at com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage(DefaultPageCreator.java:106)
    at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:433)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:311)

    <THIS_SECTION_IS_PRINTED_AS_IF_IT_WERE_IN_A_LOOP>
    at com.gargoylesoftware.htmlunit.html.BaseFrame.loadInnerPageIfPossible(BaseFrame.java:149)
    at com.gargoylesoftware.htmlunit.html.BaseFrame.loadInnerPage(BaseFrame.java:99)
    at com.gargoylesoftware.htmlunit.html.HtmlPage.loadFrames(HtmlPage.java:1760)
    at com.gargoylesoftware.htmlunit.html.HtmlPage.initialize(HtmlPage.java:194)
    at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:440)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:311)
    </THIS_SECTION_IS_PRINTED_AS_IF_IT_WERE_IN_A_LOOP>

    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:311)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:373)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:358)
    at main.Main.<init>(Main.java:42)
    at main.Main.main(Main.java:23)

"VM Thread" prio=10 tid=0x094fe000 nid=0x534c runnable 

"GC task thread#0 (ParallelGC)" prio=10 tid=0x09489800 nid=0x534a runnable 

"GC task thread#1 (ParallelGC)" prio=10 tid=0x0948ac00 nid=0x534b runnable 

"VM Periodic Task Thread" prio=10 tid=0x70207000 nid=0x5353 waiting on condition 

JNI global references: 1234

2011-08-2603:15:45
全线程转储Java热点（TM）服务器VM（20.1-b02混合模式）：
“附加侦听器”守护程序prio=10 tid=0x09520400 nid=0x5363等待条件[0x00000000]
java.lang.Thread.State:可运行
“com.gargoylesoftware.htmlunit的JS执行器。WebClient@a7c45e“守护进程prio=10 tid=0x6feb7400 nid=0x5356等待条件[0x6fcfe000]
java.lang.Thread.State:定时等待（休眠）
位于java.lang.Thread.sleep（本机方法）
在com.gargoylesoftware.htmlunit.javascript.background.JavaScriptExecutor.run（JavaScriptExecutor.java:166）上
运行（Thread.java:662）
“低内存检测器”守护程序prio=10 tid=0x70204c00 nid=0x5352可运行[0x00000000]
java.lang.Thread.State:可运行
“C2编译器线程1”守护程序prio=10 tid=0x70202800 nid=0x5351可运行[0x00000000]
java.lang.Thread.State:可运行
“C2编译器线程0”守护进程prio=10 tid=0x70200800 nid=0x5350等待条件[0x00000000]
java.lang.Thread.State:可运行
“信号调度器”守护程序prio=10 tid=0x09514c00 nid=0x534f runnable[0x00000000]
java.lang.Thread.State:可运行
Object.wait（）中的“Finalizer”守护程序prio=10 tid=0x09503400 nid=0x534e[0x70798000]
java.lang.Thread.State:正在等待（在对象监视器上）
在java.lang.Object.wait（本机方法）
-等待（java.lang.ref.ReferenceQueue$Lock）
位于java.lang.ref.ReferenceQueue.remove（ReferenceQueue.java:118）
-锁定（java.lang.ref.ReferenceQueue$Lock）
位于java.lang.ref.ReferenceQueue.remove（ReferenceQueue.java:134）
位于java.lang.ref.Finalizer$FinalizerThread.run（Finalizer.java:159）
对象中的“引用处理程序”守护程序prio=10 tid=0x09501c00 nid=0x534d.wait（）[0x707e9000]
java.lang.Thread.State:正在等待（在对象监视器上）
在java.lang.Object.wait（本机方法）
-等待（java.lang.ref.Reference$Lock）
等待（Object.java:485）
在java.lang.ref.Reference$ReferenceHandler.run（Reference.java:116）
-锁定（一个java.lang.ref.Reference$Lock）
“主”优先级=10 tid=0x09482400 nid=0x5349可运行[0xb6c34000]
java.lang.Thread.State:可运行
位于net.sourceforge.htmlunit.corejs.javascript.ScriptableObject.getSlot（ScriptableObject.java:2603）
位于net.sourceforge.htmlunit.corejs.javascript.ScriptableObject.defineProperty（ScriptableObject.java:1699）
位于com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.configureConstantsPropertiesAndFunctions（JavaScriptEngine.java:350）
位于com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.configureClass（JavaScriptEngine.java:330）
在com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.init（JavaScriptEngine.java:199）上
在com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.access$000（JavaScriptEngine.java:79）
位于com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$1.run（JavaScriptEngine.java:146）
位于net.sourceforge.htmlunit.corejs.javascript.Context.call（Context.java:537）
位于net.sourceforge.htmlunit.corejs.javascript.ContextFactory.call（ContextFactory.java:538）
在com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.initialize（JavaScriptEngine.java:157）上
位于com.gargoylesoftware.htmlunit.WebClient.initialize（WebClient.java:1141）
位于com.gargoylesoftware.htmlunit.WebWindowImpl.setEnclosedPage（WebWindowImpl.java:109）
在com.gargoylesoftware.htmlunit.html.FrameWindow.setEnclosedPage（FrameWindow.java:102）上
位于com.gargoylesoftware.htmlunit.html.HTMLParser.parse（HTMLParser.java:200）
位于com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml（HTMLParser.java:179）
在com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage上（DefaultPageCreator.java:221）
在com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage（DefaultPageCreator.java:106）
在com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto（WebClient.java:433）上
在com.gargoylesoftware.htmlunit.WebClient.getPage（WebClient.java:311）上
位于com.gargoylesoftware.htmlunit.html.BaseFrame.（BaseFrame.java:73）
位于com.gargoylesoftware.htmlunit.html.HtmlInlineFrame.（HtmlInlineFrame.java:46）
在com.gargoylesoftware.htmlunit.html.DefaultElementFactory.createElementNS（DefaultElementFactory.java:288）
位于com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.startElement（HTMLParser.java:506）
位于org.apache.xerces.parsers.AbstractSAXParser.startElement（未知源）
位于org.cyberneko.html.HTMLTagBalancer.callStartElement（HTMLTagBalancer.java:1136）
位于org.cyberneko.html.HTMLTagBalancer.startElement（HTMLTagBalancer.java:742）
位于org.cyberneko.html.filters.DefaultFilter.startElement（DefaultFilter.java:136）
位于org.cyberneko.html.filters.NamespaceBinder.startElement（NamespaceBinder.java:278）
位于org.cyberneko.html.HTMLScanner$ContentScanner.scanStartElement（HTMLScanner.java:2652）
位于org.cyberneko.html.HTMLScanner$ContentScanner.scan（HTMLScanner.java:2022）
位于org.cyberneko.html.HTMLScanner.scanDocument（HTMLScanner.java:908）
位于org.cyberneko.html.HTMLConfiguration.parse（HTMLConfiguration.java:499）
位于org.cyberneko.html.HTMLConfiguration.parse（HTMLConfiguration.java:452）
位于org.apache.xerces.parsers.XMLParser.parse（未知源）
位于com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.parse（HTMLParser.java:789）
位于com.gargoylesoftware.htmlunit.html.HTMLParser.parse（HTMLParser.java:225）
位于com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml（HTMLParser.java:179）
在com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage上（DefaultPageCreator.java:221）
在com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage（DefaultPageCreator.java:106）
位于com.gargoylesoftware.htmlunit.WebClient.loadWebRes
try {
    HtmlPage page = webClient.getPage("http://www.w3schools.com/HTML/tryit.asp?filename=tryhtml_noframes");
    HtmlInlineFrame frame = page.getFirstByXPath("//iframe[@name='view']");
    page = webClient.getPage(page.getFullyQualifiedUrl(frame.getSrcAttribute()));
    System.out.println(page.asXml());
} catch (Exception e) {
    e.printStackTrace();
}