说明

开发中遇到jar包冲突问题，可以使用以下代码定位当前jvm加载的类是从哪个jar包中来的，根据输出的物理文件路径，定位问题。

使用方法

className参数为类的全名，不需要.class后缀，如 srcAdd.jsp?className=java.net.URL

代码：

<%@page contentType="text/html; charset=GBK"%>
<%@page import="java.security.*,java.net.*,java.io.*"%>
<%!
    public static URL getClassLocation(final Class cls) {
        if (cls == null)throw new IllegalArgumentException("null input: cls");
        URL result = null;
        final String clsAsResource = cls.getName().replace('.', '/').concat(".class");
        final ProtectionDomain pd = cls.getProtectionDomain();
        // java.lang.Class contract does not specify if 'pd' can ever be null;
        // it is not the case for Sun's implementations, but guard against null
        // just in case:
        if (pd != null) {
            final CodeSource cs = pd.getCodeSource();
            // 'cs' can be null depending on the classloader behavior:
            if (cs != null) result = cs.getLocation();
            if (result != null) {
                // Convert a code source location into a full class file location
                // for some common cases:
                if ("file".equals(result.getProtocol())) {
                    try {
                        if (result.toExternalForm().endsWith(".jar") ||
                                result.toExternalForm().endsWith(".zip"))
                            result = new URL("jar:".concat(result.toExternalForm())
                                    .concat("!/").concat(clsAsResource));
                        else if (new File(result.getFile()).isDirectory())
                            result = new URL(result, clsAsResource);
                    }
                    catch (MalformedURLException ignore) {}
                }
            }
        }
        if (result == null) {
            // Try to find 'cls' definition as a resource; this is not
            // document．d to be legal, but Sun's implementations seem to         //allow this:
            final ClassLoader clsLoader = cls.getClassLoader();
            result = clsLoader != null ?
                    clsLoader.getResource(clsAsResource) :
                    ClassLoader.getSystemResource(clsAsResource);
        }
        return result;
    }
%>
<html>
<head>
    <title>srcAdd.jar</title>
</head>
<body bgcolor="#ffffff">
使用方法，className参数为类的全名，不需要.class后缀，如
srcAdd.jsp?className=java.net.URL
<%
    try
    {
        String classLocation = null;
        String error = null;
        String className = request.getParameter("className");

        classLocation =  ""+getClassLocation(Class.forName(className));
        if (error == null) {
            out.print("类" + className + "实例的物理文件位于：");
            out.print("<hr>");
            out.print(classLocation);
        }
        else {
            out.print("类" + className + "没有对应的物理文件。<br>");
            out.print("错误：" + error);
        }
    }catch(Exception e)
    {
        out.print("异常。"+e.getMessage());
    }
%>
</body>
</html>

解决jar包冲突

说明

使用方法

代码：