利用Gson转换json数据和java对象

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一直在使用json-lib包
每次得到数据都得转换半天 除了实体类外还要写一个影射类 非常的麻烦
利用Gson包就可以直接导入整个实体类以转换 不过需要的是json的数据名称与实体类的名称要一致
首先是实体类

public class User {
    private String userName;
    private String psw;
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPsw() {
        return psw;
    }
    public void setPsw(String psw) {
        this.psw = psw;
    }
    public User(String userName, String psw) {
        super();
        this.userName = userName;
        this.psw = psw;
    }
    @Override
    public String toString() {
        return "userName= " + userName + " psw= " + psw;
    }

}

利用Gson输出Json数据
—-原版的利用影射类

public class MyServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;
    public MyServlet() {
        super();
    }
    public void destroy() {
        super.destroy(); 
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        JSONArray array = new JSONArray();
         JdbcTemplate template=new JdbcTemplate();
         List<User>  list=null;         
         try {
             list=(List<User>)template.findAll("select * from User", new UserMapping());
//数据库已连接好的情况下...User是表 UserMapping是实体类
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
             for (int i = 0; i < list.size(); i++) 
                 {
                 JSONObject temp = new JSONObject()   
                 .element( "Name",list.get(i).getUserName() )  
                 .element( "password", list.get(i).getPsw() );           
                 array.add(temp);    }
            out.print(array.toString());
            System.out.println(array.toString());
        } 
        }

现在利用Gson就可以了

                Gson gson = new Gson();
        String msgJson = gson.toJson(list);

利用Gson转换json数据
转换单一字符串 如：
[{“userName”:”userName”,”pwd”:123}]
User user= gson.fromJson(str, User.class);
转换字符串组， 如：

List<User> users = gson.fromJson(str, new TypeToken<List<User>>(){}.getType());
for(int i = 0; i < users.size() ; i++)
{
     User user = users.get(i);
     System.out.println(user.toString());//这里想做什么都可以了 记住必须是实体类的名字和json中传送的名字相同
}

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