srcAdd.jsp用于解决java.lang.NoSuchMethodError

来源：互联网发布：数据仓库数据加工编辑：程序博客网时间：2024/06/10 10:56

在实际开发中，经常会遇到jar包冲突而抛出的：java.lang.NoSuchMethodError
,排查起来非常的麻烦。本JSP页面的功能就是用于java类路径定位，使用时将srcAdd.jsp放置在项目的根路径下，项目运行起来之后，在地址栏输入URL，如 .../srcAdd.jsp?className=java.net.URL即可查看类所在的路径

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>  <%@ 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>

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