在Action中获取文件的路径，读写文件

ActionContext ac = ActionContext.getContext(); 

ServletContext sc = (ServletContext) ac.get(ServletActionContext.SERVLET_CONTEXT); 

String x = sc.getRealPath("/");

接着进入项目的工作空间，workspace1\bams\bin\dagl\WEB-INF\config\下找到了我们刚刚在eclipse环境中添加的

default.key.

in = new FileInputStream(x+"WEB-INF/config/default.key");

br = new BufferedReader(new InputStreamReader(in));

String code = br.readLine();

2)java项目向某一个文件中写一个字符串

File keyFile = new File("default.key");
if (!keyFile.exists()) {
keyFile.createNewFile();
}
FileWriter fw = new FileWriter(keyFile);
fw.write(finalcode);
fw.close();