从/JsonTest/OutJson中获取json包装的数据
index.jsp

    <script>
        $(function(){
        	$("#btn").click(function(){
        		var url="/JsonTest/OutJson";
        	$.ajax({
        				url:url,
        				type:"get",
        				dataType:"json",
        				success:function(d){
        					var $pro=$("#proId");
        					$(d).each(function(){
        						$pro.append($("<option val>"+this.name+"</option>"+"<option>"+this.password+"</option>"));
        					});
        				},
        				error:function(){},
        	});
        	});
        })
        </script>
        <input type="button" id="btn" value=>
        	<select id="proId" name="province">
        		<option>账号与密码</option>
        	</select>
        </body>

以下是定义一个Javabean的实体类； @WebServlet("/OutJson")给这个类命名一个访问的路径

    public class UserBean {
    	private String name;
    	private String password;
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getPassword() {
    		return password;
    	}
    	public void setPassword(String password) {
    		this.password = password;
    	}
    	@Override
    	public String toString() {
    		return "UserBean [name=" + name + ", password=" + password + "]";
    	}
    }

这个是index.jsp要跳转的界面

@WebServlet("/OutJson")
    public class Userservice extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	@Override
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		UserBean user=new UserBean();
    		user.setName("小明");
    		user.setPassword("123546");
    		UserBean user1=new UserBean();
    		//user1.setName("小hua");
    		//PrintWriter out=response.getWriter();
    		//out.println(JsonUtil.objToJson(user));//以下将数据发送到前端用ajax接受
    		response.getWriter().print(JsonUtil.objToJson(user));
    	}
    	@Override
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

JsonUtil是一个定义的工具类，里面的JsonUtil.objToJson(user)；就是将对象转化为String类型输出

 public class JsonUtil {
        /** * 对象转换成JSON字符串 * * @param obj * 需要转换的对象 * @return 对象的string字符 */
        public static  String objToJson(Object obj) {
            JSONObject jSONObject = JSONObject.fromObject(obj);
            return jSONObject.toString();
        }
        }