我有一个 Web 应用程序，其中包含一些以前在 Linux 机器上运行的 JSP。我需要让它在运行 Tomcat 5.5.29 的 Windows XP SP3 机器上运行。现在几乎一切正常，但只有一项:该应用程序能够将配置文件写入其 Windows 目录(即 C:\Program Files\Apache\Tomcat\webapps\myapp)。但是当它尝试这样做时，应用程序无法打开 FileOutputStream(返回 null)。如果我放下路径说明符，让它打开文件，它会在 Tomcat 目录中成功打开它。

第一行失败，第二行成功:

//  outputFile2 = new PrintWriter(new FileOutputStream(basePathName + "programAll.txt", false));
    outputFile2 = new PrintWriter(new FileOutputStream("programAll.txt", false));

这是创建 basePathName 的代码:

    String basePathName = getBaseFilePath();  
    ...
    public String getBaseFilePath()
            {
            String curDir = System.getProperty("catalina.home");  
            curDir = curDir + "/webapps/pubmed/"; 
            curDir = "file:///" + formatPathNameForOS(curDir);
            return curDir;
            }

   public String formatPathNameForOS(String pathName)
        {
        if (codeIsOnWindows())
            {
            pathName = pathName.replace('/','\\');
            }
        else
            {
            pathName = pathName.replace('\\','/');
            }
        return pathName;
    }

这是异常消息:

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:460)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:321)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:257)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
root cause

java.lang.NullPointerException
    org.apache.jsp.updateMemberLists_jsp._jspService(updateMemberLists_jsp.java:1492)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:321)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:257)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

这是堆栈跟踪:

Aug 6, 2010 1:20:39 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
    at org.apache.jsp.updateMemberLists_jsp._jspService(updateMemberLists_jsp.java:1492)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:321)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:257)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.globus.tomcat.coyote.valves.HTTPSValve55.invoke(HTTPSValve55.java:45)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Thread.java:595)

我查看了 updateMembersLists_jsp.java，这里是出现空指针的部分:

//create a file to write to the output
PrintWriter outputFile2 = null;
try
    {
    outputFile2 = new PrintWriter(new FileOutputStream(basePathName + "programAll.txt", false));
//  outputFile2 = new PrintWriter(new FileOutputStream("programAll.txt", false));
    }
    catch (FileNotFoundException e)
        {
        out.write("<p><font color='red'>Error Saving</font></p>");
        }
outputFile2.print(output);  // THIS IS LINE 1492 -- NULL POINTER
outputFile2.close();

此外:我们现在从根目录而不是 Program Files 运行 Tomcat。我已经检查了 basePathName 并且计算正确。

现在我发现 Tomcat 的策略设置可能需要调整。我将以下几行添加到 catalina.policy 希望它能解决问题:

// The permissions granted to the pubmed webapp
grant codeBase "file:${catalina.home}/webapps/pubmed/-" {
        permission java.io.FilePermission "${catalina.home}/webapps/pubmed/-", "read, write";
        permission java.io.FilePermission "${catalina.home}/webapps/pubmed/*", "read, write";
};

这似乎没有任何效果。运行 tomcat 的 Windows 用户对 pubmed 目录具有读/写权限。除了这个 webapp 将文件写入它自己的目录似乎有问题之外，我还缺少什么？

肖恩