java - Servlet - 包括来自另一个类的其他 jar

Question

我有一个servlet使用另一个 class命名Converter ，这个类使用了我放入 WEB-INF/lib 中的一些外部 jar。但当尝试使用此类时，我仍然得到 java.lang.ClassNotFoundException ，我在这里尝试了无数的解决方案，但仍然没有一个有效:

• 将 jar 放入 classpath .
• 将 jar 放在 WEB-INF/classes 下

它们都不起作用，这是我的 servlet 中的相关部分:

private Converter htmlCon = new Converter(webInfPath);

protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        StringBuffer jb = new StringBuffer();
        String line = null;
        try {
            BufferedReader reader = request.getReader();
            while ((line = reader.readLine()) != null) {
                jb.append(line);
            }
        } catch (IOException IOE) {
            IOE.printStackTrace();
        }
        try {
            htmlCon.createPdf(jb.toString(), "pdf.pdf");
        } catch (DocumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

和Converter :

package com.mataf.converters;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
//the external jars
import org.xhtmlrenderer.pdf.ITextRenderer;

import com.lowagie.text.DocumentException;

public class Converter {

    private Types m_type;
    private String m_pathToCreateFileIn;

    public Converter(String i_path) {
        this.m_pathToCreateFileIn = i_path;
    }

    public void createPdf(String html, String fileName) throws IOException, DocumentException{

        ITextRenderer renderer = new ITextRenderer();
        // if you have html source in hand, use it to generate document object
        renderer.setDocumentFromString( html);
        renderer.layout();
        String fileNameWithPath = m_pathToCreateFileIn + File.separator + "PDF-FromHtmlString.pdf";
        FileOutputStream fos = new FileOutputStream( fileNameWithPath );
        renderer.createPDF( fos );
        fos.close();
        System.out.println( "File 2: '" + fileNameWithPath + "' created." );
        System.out.println(html);
        System.out.println(fileName);
    }

}

完整stacktrace :

com.ibm.ws.webcontainer.servlet.ServletWrapper run SRVE8052E: Logging ClassNotFoundException
                                 java.lang.ClassNotFoundException: class java.lang.NullPointerException: null
    at java.beans.Beans.instantiate(Beans.java:190)
    at java.beans.Beans.instantiate(Beans.java:75)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper$1.run(ServletWrapper.java:1461)
    at com.ibm.ws.security.util.AccessController.doPrivileged(AccessController.java:118)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper.loadServlet(ServletWrapper.java:1450)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper.load(ServletWrapper.java:1348)
    at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:980)
    at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3703)
    at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304)
    at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:962)
    at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1662)
    at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195)
    at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:458)
    at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:522)
    at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:311)
    at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:87)
    at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
    at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
    at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
    at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
    at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
    at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
    at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
    at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1783)

Answer 1

请参阅此链接以了解您所看到的异常的原因:Odd behavior in WAS 7.0: java.lang.ClassNotFoundException: class java.lang.NullPointerException: null

“WebSphere Application Server 中包含的 Java 6 版本丢失了对 Java 错误 4256569 的修复，这掩盖了失败的实际原因。”

如果您更新了 websphere 应用程序中的 Java 版本，那么问题的实际原因应该很明显。