try{
    //需要生成 .txt的数据文件 
    //FileWriter fw=new FileWriter(Messages.getString("VoteDiaochaAction.3"));

    //建立FileWriter对象，并实例化fw            
    FileWriter fw=null;
    try {

     //column.txt
     fw = new FileWriter   ("../webapps/vote/amcolumn/data/column.txt");
     } catch (RuntimeException e) {
           e.printStackTrace();
     }    
     
     /*
      //Java文件路径问题
       System.out.println(
             Thread.currentThread().getContextClassLoader().getResource(""));
       System.out.println(VoteDiaochaAction.class.getClassLoader().getResource(""));
       System.out.println(ClassLoader.getSystemResource(""));
       System.out.println(VoteDiaochaAction.class.getResource(""));
       System.out.println(VoteDiaochaAction.class.getResource("/"));
       System.out.println(new File("column2.txt").getAbsolutePath());
       System.out.println(System.getProperty("user.dir"));
     */
    
       //FileWriter fw=new FileWriter ("/webRoot/amcolumn/data/column.txt");            

       //将字符串写入文件

       fw.write(data);            
       fw.close();
    } catch (Exception e) {
       e.printStackTrace();
    }

获得文件真实路径

string file_real_path=request.getRealPath("mypath/filename");

通常使用request.getRealPath("/");