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我在我的项目中使用 CUPS4J，它依赖于 http-client、http-core 和 slf4j。

为了解决依赖关系，我们使用 Maven，我定义了如下依赖关系：

<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>

cups4j 依赖项位于我们的 ArtiFactory 服务器上（我在网上找不到）。

如果我创建一个示例main方法来打印一些文档并将其作为 java 应用程序启动，那么一切都像一个魅力。

当我将我的类发布到 Websphere 服务器并从网页调用该方法时，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);
    }
}

似乎它已经存在并且与Apache 库HttpUriRequest提供的存在冲突，但是如果我尝试从 中删除该依赖项，我会得到该类的一个。httpclientpom.xmlNoClassDefFoundException

如果重要的话，我的 IDE 是 Eclipse Luna。

我该如何解决这个异常？

4

1 回答 1

0

WebSphere 还使用 httpclient 库，它可能与您提供的库发生冲突。尝试通过在管理控制台中创建隔离的共享库Environment > Shared Libraries。将http-*,slf4j和cups4jjars 放在那里并将共享库与您的应用程序相关联。

于 2014-11-06T16:56:26.477 回答