Websphere上的java.lang.LinkageError尝试加载HttpUriRequest

Question

我使用的CUPS4J用于我的项目，该项目取决于http-client，http-core和slf4j。

要解决我们使用Maven的依赖，和我已经定义的依赖关系如下：

<dependency> 
    <groupId>cups4j</groupId> 
    <artifactId>cups4j</artifactId> 
    <version>0.6.4</version> 
</dependency> 

<dependency> 
    <groupId>org.apache.httpcomponents</groupId> 
    <artifactId>httpclient</artifactId> 
    <version>4.0.3</version> 
</dependency> 

<dependency> 
    <groupId>org.apache.httpcomponents</groupId> 
    <artifactId>httpcore</artifactId> 
    <version>4.1</version> 
</dependency> 

<dependency> 
    <groupId>org.slf4j</groupId> 
    <artifactId>slf4j-api</artifactId> 
    <version>1.7.7</version> 
</dependency> 

的cups4j依赖是我们artifactory的服务器上（我不能在网上找到它）。

如果我创建一个样本main方法来打印某些文档并将其作为Java应用程序启动，那么所有内容都可以作为魅力使用。

当我发表我的班到WebSphere服务器，并调用该方法从一个网页，它会生成一个java.lang.LinkageError。

这是堆栈跟踪的相关部分：

Caused by: java.lang.LinkageError: loader constraint violation: loader "org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader@208c132" previously initiated loading for a different type with name "org/apache/http/client/methods/HttpUriRequest" defined by loader "com/ibm/ws/classloader/CompoundClassLoader@1e0f797" 
    at java.lang.ClassLoader.defineClassImpl(Native Method) 
    at java.lang.ClassLoader.defineClass(ClassLoader.java:260) 
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.defineClass(DefaultClassLoader.java:188) 
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClass(ClasspathManager.java:580) 
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findClassImpl(ClasspathManager.java:550) 
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClassImpl(ClasspathManager.java:481) 
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass_LockClassName(ClasspathManager.java:460) 
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:447) 
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:216) 
    at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:393) 
    at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:469) 
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:422) 
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410) 
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107) 
    at java.lang.ClassLoader.loadClass(ClassLoader.java:612) 
    at org.apache.http.impl.client.AbstractHttpClient.determineTarget(AbstractHttpClient.java:584) 
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:708) 
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:700) 
    at org.cups4j.operations.IppOperation.sendRequest(IppOperation.java:207) 
    at org.cups4j.operations.IppOperation.request(IppOperation.java:76) 
    at org.cups4j.CupsPrinter.print(CupsPrinter.java:113) 
    at it.dropcomp.tasks.print.PrinterService.printPDF(PrinterService.java:160) 

这是打印PDF（内部it.dropcomp.tasks.print.PrinterService）的方法：

public void printPDF() throws RemoteServiceException { 
    /* 
    * generatedPDF is defined as File, and it's properly initialized 
    * before calling this method. 
    */ 
    if(generatedPDF == null) { 
     throw new RemoteServiceException("You must generate a file first!"); 
    } 
    try { 
     CupsPrinter selectedPrinter = new CupsPrinter(
      new URL(Constants.PRINTER_FULL_URL), 
      Constants.PRINTER_NAME, true 
     ); 
     InputStream is = new FileInputStream(generatedPDF); 
     PrintJob pj = new PrintJob.Builder(is).build(); 
     selectedPrinter.print(pj); //this is line 160 
    } catch (Exception e) { 
     LOG.error("Exception", e); 
     throw new RemoteServiceException(e); 
    } 
} 

似乎HttpUriRequest已经存在，使得冲突一个由Apache的httpclient库提供，但如果我尝试从pom.xml去除依赖，我得到了NoClassDefFoundException该类。

如果很重要，我的IDE是Eclipse Luna。

我该如何解决这个异常？

Answer 1

WebSphere还使用httpclient库，它可能与您提供的库冲突。 尝试通过Environment > Shared Libraries在管理控制台中创建独立的共享库。将http-*,slf4j和cups4j放置在那里，并将共享库与您的应用程序相关联。