对于json
从servlet中返回给ajax的dataType类型可以是text,json
1、在servlet中构造json文本，再response.getWriter()给ajax，返回json text文本
servlet中，一面一段写在doPost或doGet中，但要相互调用this.doGet(rq,rs)或this.doGet(rq,rs)
用jquery的ajax异步提交，数据必须有一个明确的ID（不再是name，和form提交方式不一样），比如下面jsp中的username就是ID
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;;charset=utf-8");//注意要是返回文本，那么类型为text/html String username1 = request.getParameter("username"); String username = URLDecoder.decode(username1,"UTF-8"); StringBuilder message = new StringBuilder(""); if(username!=null) { EmployeeDao employeeDao = new EmployeeDao(); ArrayList employees = employeeDao.select(username); if(employees!=null&&employees.size()>0) { message.append("{\"emp\":[");// for(Employee employee: employees)// { //对于这样的集合类型的数据，不推荐使用构造字符串的方式来构造json数组// System.out.println(employee.getEmpNo());// message.append("{\"eno\":"+employee.getEmpNo()+","+"\"ename\""+employee.getEname()+"}");// } //为了说明构造json文本，仅使用2条记录 message.append("{\"eno\":"+"\""+employees.get(0).getEmpNo()+"\""+","+"\"ename\""+":"+"\""+employees.get(0).getEname()+"\""+"}"); message.append(","); message.append("{\"eno\":"+"\""+employees.get(1).getEmpNo()+"\""+","+"\"ename\""+":"+"\""+employees.get(1).getEname()+"\""+"}"); message.append("]}"); } PrintWriter out = response.getWriter(); out.println(new String(message)); } 在ajax中
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>Insert title here 输入用户名
2、用字符串构造json数据，返回json对象
servlet中返回application/json
ajax中dateType用json
servlet代码，和上面没有什么区别，主要是把contentype改为application/json
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("application/json;charset=utf-8"); String username1 = request.getParameter("username"); String username = URLDecoder.decode(username1,"UTF-8"); StringBuilder message = new StringBuilder(""); if(username!=null) { EmployeeDao employeeDao = new EmployeeDao(); ArrayList employees = employeeDao.select(username); if(employees!=null&&employees.size()>0) { message.append("{\"emp\":[");// for(Employee employee: employees)// { //对于这样的集合类型的数据，不推荐使用构造字符串的方式来构造json数组// System.out.println(employee.getEmpNo());// message.append("{\"eno\":"+employee.getEmpNo()+","+"\"ename\""+employee.getEname()+"}");// // } //为了说明构造json文本，仅使用2条记录 message.append("{\"eno\":"+"\""+employees.get(0).getEmpNo()+"\""+","+"\"ename\""+":"+"\""+employees.get(0).getEname()+"\""+"}"); message.append(","); message.append("{\"eno\":"+"\""+employees.get(1).getEmpNo()+"\""+","+"\"ename\""+":"+"\""+employees.get(1).getEname()+"\""+"}"); message.append("]}"); } System.out.println(message); PrintWriter out = response.getWriter(); out.println(new String(message)); } } jsp中代码
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>Insert title here 输入用户名
3、返回json对象，但是在servlet中直接用把一个数组或集合转换成为json类型的数组对象
如果
说明没有导包，注意导入相关的jar包
(注：导入最新的 3.1 版本会继续报如下错误)
参考：http://blog.csdn.net/wugewuge/article/details/8074272
在servlet写法
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("application/json;charset=utf-8"); String username1 = request.getParameter("username"); String username = URLDecoder.decode(username1,"UTF-8"); StringBuilder message = new StringBuilder(""); if(username!=null) { EmployeeDao employeeDao = new EmployeeDao(); ArrayList employees = employeeDao.select(username); JSONArray jsonArray=JSONArray.fromObject(employees); PrintWriter out = response.getWriter(); out.println(jsonArray.toString());//在jsp中的数据类型dataType："json" } } 在jsp中:
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>Insert title here 输入用户名
另外一篇参考: