Java WebStart速度慢，从无效文件夹中请求库 [英] Java WebStart slow, requesting libraries from invalid folder

问题描述

问题和疑问：Java webstarted应用程序在基础文件夹而不是./lib中查找其类。

Problem and question: Java webstarted app looking for its classes in base folder instead of ./lib.

正如 Java Web Start应用程序反复询问未存在的文件我已经关闭 jar签名，以排除安全问题问题仍然存在。

As suggested in similar question at Java Web Start applications ask repeatedly for un-existing files I have turned off the jar signing, to rule out the security issue, and the problem persists.

下面找到关于这个简单的java程序网络内容的简洁示例：

Below find the clean example on what is going over the network for this simple java program:

public static void main(String[] args) {
    // TODO code application logic here
    System.out.println("Hello World! Initializing the class from the jar residing in lib/ folder. Expecting heavy network traffic...");

    //This class resides in lib/SampleJavaLibrary.jar
    //Initializing it just to excercise the class loader problem
    CDummyClass sDummy = new CDummyClass();

    System.out.println("Done");

}

在网络上（通过wireshark），可以观察到重复对基本文件夹中的jar请求，在一些调用中，我最多计算10次重试，由web服务器回复404.最终，loadClass成功，但仅在10或更多请求不存在的jar之后。将其与给定程序中正在访问的类的数量相乘，最终会导致初始化非常慢。
在这个简单的例子中，这个简单的类只有仅2次重试。

On the network (by wireshark), one can observe repeated requests for jars in base folder, On some calls I counted up to 10 retries, replied by web server with 404. Ultimately, the loadClass is successful, but only after 10 or more requests for nonexisting jars. Multiply this with the number of classes being accessed in given program, and you end up with very slow initialization. In this simple case, there are "only" 2 retries for this simple class.

这一切都正常开始，罐装了，一切都很好，不错：

It all starts normal, the jars are loaded, all is good and nice:

6   0.020921    192.168.1.35    192.168.1.130   HTTP    GET /mnt/vbox/workspace/WebStartSample/distC/launch.jnlp HTTP/1.1
8   0.028092    192.168.1.130   192.168.1.35    HTTP    HTTP/1.1 200 OK  (application/x-java-jnlp-file)
10  0.514038    192.168.1.35    192.168.1.130   HTTP    GET /mnt/vbox/workspace/WebStartSample/distC/lib/SampleJavaLibrary.jar HTTP/1.1 
11  0.520688    192.168.1.130   192.168.1.35    HTTP    HTTP/1.1 200 OK  (application/java-archive)
12  0.618640    192.168.1.35    192.168.1.130   HTTP    GET /mnt/vbox/workspace/WebStartSample/distC/WebStartSample.jar HTTP/1.1 
14  0.652541    192.168.1.130   192.168.1.35    HTTP    HTTP/1.1 200 OK  (application/java-archive)

这是故障开始的地方，在图书馆班级电话会议上：

This is where the trouble begins, at library class call:

16  0.943801    192.168.1.35    192.168.1.130   HTTP    GET /mnt/vbox/workspace/WebStartSample/distC/SampleJavaLibrary.jar HTTP/1.1 
18  0.991748    192.168.1.130   192.168.1.35    HTTP    HTTP/1.1 404 Not Found  (text/html)
22  0.997281    192.168.1.35    192.168.1.130   HTTP    GET /mnt/vbox/workspace/WebStartSample/distC/SampleJavaLibrary.jar HTTP/1.1 
24  1.004799    192.168.1.130   192.168.1.35    HTTP    HTTP/1.1 404 Not Found  (text/html)

最终，在上面重试之后，正在找到并初始化类（！），很可能来自已经存在的jar，它是在应用程序启动时加载的。

Ultimately, after above retrying, the class is being found and initialized (!), most likely from the already existing jar, which was loaded at application startup.

为什么jnlp类加载器会查看基本文件夹，为什么这么多次重试都超出了我的范围。我确实尝试在调试器下运行，但是找不到类加载器的源代码并且无法自己解决。

Why is jnlp class loader looking into base folder, and why for so many retries, is beyond me. I did tried to run under debugger, but could not find the sources for class loaders and could not figure it myself.

FWIW这里是我的jnlp文件，是的，我我尝试了更新标签的所有变体，懒惰，渴望，没有变化

FWIW here is my jnlp file, and yes, I did tried all variations of update tag, lazy, eager, no changes

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<jnlp codebase="http://mydebian.mydomain/mnt/vbox/workspace/WebStartSample/distC"    href="launch.jnlp" spec="1.0+">
    <information>
        <title>WebStartSample</title>
        <vendor>user</vendor>
        <homepage href=""/>
        <description>WebStartSample</description>
        <description kind="short">WebStartSample</description>

    </information>
<update check="always"/>

    <resources>
<j2se version="1.5+"/>
<jar href="WebStartSample.jar" main="true"/>


    <jar href="lib/SampleJavaLibrary.jar"/>
</resources>
    <application-desc main-class="webstartsample.Main">

    </application-desc>
</jnlp>

我怀疑JNLPClassLoader（）有问题，这是webstart中使用的特定加载器。

I suspect there is something wrong with the JNLPClassLoader(), that is the particular loader used within the webstart.

问候，

Robert

推荐答案

感谢大家的建议。这是安德鲁暗示为罐子编制索引，它指出了正确的方向......

Thanks everyone for suggestions. It was Andrew hint to 'index the jars' which pointed me to the right direction...

即罐子（我现在选择的IDE，Netbeans） 已编入索引。但是，主jar中的META-INF / INDEX.LIST包含对其他jar的引用，就好像它们位于主jar的当前文件夹中一样。

Namely, the jars (produced my current IDE of choice, Netbeans) were indexed. However, the META-INF/INDEX.LIST within the main jar contained the references to other jars as if they were in current folder, next to the main jar.

JarIndex-Version: 1.0

WebStartSample.jar
webstartsample

SampleJavaLibrary.jar
newpackage

这导致jnlpClassLoader（），使用主索引，并在codebase url中查找jar，而实际上它们位于。 / lib url子文件夹。

That resulted in jnlpClassLoader(), using the main index, and looking for jars in codebase url, while they actually resided under ./lib url subfolder.

这是正确的索引（手动重新创建）的样子：

This is how the correct index (recreated manually) looks:

JarIndex-Version: 1.0

WebStartSample.jar
webstartsample

lib/SampleJavaLibrary.jar
newpackage

为了使问题变得更糟，这样的webstarted应用程序不会失败，他们只会先在错误的位置查找类/ jar，然后最终找到它们，大概已经加载了bu jnlp loader，如原始问题所述。

To make the problem worst, such webstarted application would not fail, they would just look for classes/jars in wrong places first, and then eventually find them, presumably already loaded bu jnlp loader as described in original question.

简而言之，这与Netbeans构建和打包程序有关。

Briefly, this IS related to Netbeans build and packaging procedure.

我的即时修复是禁用jar索引，这导致了正确和最小的网络流量，并大大改善了应用程序初始化。

My immediate fix was disabling the jar indexing, and that resulted in correct and minimal network traffic, and greatly improved application initialization.

要在Netbeans中执行此操作，请转到工具 - >选项 - >其他 - > Ant->属性并添加 jar.index = false

To do it in Netbeans, go to Tools->Options->Miscellaneous->Ant->Properties and add jar.index=false

正确的解决方法是让Netbeans正确地对jar进行索引，但这是另一个问题。

Proper fix would be to make Netbeans index the jar correctly but that is the another question.

再次感谢大家的建议。

ps。

• janela util在我的jnlp中没有发现重大错误


• 包元素包括不做任何更改


• mydebian指的是我的服务器，客户端是win7，包含所有最新和最好的java运行时和jdks，包括netbeans 6.9 （也用7.0测试，产生相同的问题索引）

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