spring mvc（五）CRUD及PUT/DELETE参数

使用springmvc实现基于页面的增删改查，只要对Controller不同方法返回不同的的View（页面或json/xml)即可。
本节示例对Teacher集合进行CRUD的操作。

1.设计
设计Teacher模块前台需要一个页面进行列表展示和交互，通过ajax异步提交form并返回json结果；后台需要提供查询列表、创建、删除、修改、查询等方法。考虑到分页需求，还需要一个统计总数方法。

地址	请求方法	说明
/teacher	GET	模块入口，返回jsp
/teacher/list	GET	查询teacher集合
/teacher/count	GET	查询teacher数量
/teacher/get	GET	根据id查询某个teacher
/teacher/save	POST	创建新teacher，content中包含资源内容
/teacher/update	POST	更新teacher，content中包含资源内容
/resource/remove	GET	根据id删除teacher

2.Teacher POJO、DAO、SERVICE
在com.sunbin.test.teacher包下创建POJO、DAO、SERVICE。
Teacher类：

package com.sunbin.test.teacher.pojo;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "Teacher")
public class Teacher {

	private int id;
	private int age;
	private String name;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "Teacher [id=" + id + ", age=" + age + ", name=" + name + "]";
	}
}

@XmlRootElement(name = "Teacher")注解使得Teacher类可以被转换成xml/json格式输出。
TeacherService接口：

package com.sunbin.test.teacher.service;

import java.util.List;

import com.sunbin.test.teacher.pojo.Teacher;

public interface TeacherService {

	@SuppressWarnings("rawtypes")
	public List list();

	public int count();

	public void save(Teacher teacher);

	public void remove(Teacher teacher);

	public void update(Teacher teacher);

	public Teacher get(Teacher teacher);

}

定义了6个服务层抽象方法：查询列表、统计总数、创建、删除、修改、查询。
TeacherDao接口：

package com.sunbin.test.teacher.dao;

import java.util.List;

import com.sunbin.test.teacher.pojo.Teacher;

public interface TeacherDao {

	@SuppressWarnings("rawtypes")
	public List list();

	public int count();

	public void save(Teacher teacher);

	public void remove(Teacher teacher);

	public void update(Teacher teacher);

	public Teacher get(Teacher teacher);

}

定义了与service接口对应的6个数据层抽象方法。

3.接口实现
示例中不使用数据库，而是使用一个List来存储Teacher集合。
TeacherDaoImpl数据层接口实现：

package com.sunbin.test.teacher.dao.impl;

import java.util.ArrayList;
import java.util.List;
import org.springframework.stereotype.Repository;

import com.sunbin.test.teacher.dao.TeacherDao;
import com.sunbin.test.teacher.pojo.Teacher;

@Repository("teacherDao")
public class TeacherDaoImpl implements TeacherDao {

	private static List<Teacher> teachers = new ArrayList<Teacher>();

	@SuppressWarnings("rawtypes")
	@Override
	public List list() {
		System.out.println("TeacherDaoImpl.list:" + teachers);
		return teachers;
	}

	@Override
	public int count() {
		System.out.println("TeacherDaoImpl.count:" + teachers.size());
		return teachers.size();
	}

	@Override
	public void save(Teacher teacher) {
		System.out.println("TeacherDaoImpl.save:" + teacher);
		int teacherId = 1;
		if (teachers.size() > 0) {
			teacherId = teachers.get(teachers.size() - 1).getId() + 1;
		}
		teacher.setId(teacherId);
		teachers.add(teacher);
	}

	@Override
	public void remove(Teacher teacher) {
		System.out.println("TeacherDaoImpl.remove:" + teacher);
		int teacherId = teacher.getId();
		for (int i = 0; i < teachers.size(); i++) {
			Teacher teacherI = teachers.get(i);
			if (teacherI.getId() == teacherId) {
				teachers.remove(i);
				return;
			}
		}
	}

	@Override
	public void update(Teacher teacher) {
		System.out.println("TeacherDaoImpl.update:" + teacher);
		int teacherId = teacher.getId();
		for (int i = 0; i < teachers.size(); i++) {
			Teacher teacherI = teachers.get(i);
			if (teacherI.getId() == teacherId) {
				teachers.remove(i);
				teachers.add(i, teacher);
				return;
			}
		}
	}

	@Override
	public Teacher get(Teacher teacher) {
		System.out.println("TeacherDaoImpl.get:" + teacher);
		int teacherId = teacher.getId();
		for (int i = 0; i < teachers.size(); i++) {
			Teacher teacherI = teachers.get(i);
			if (teacherI.getId() == teacherId) {
				return teacherI;
			}
		}
		return null;
	}

}

该类实现了数据层接口，且@Repository("teacherDao")注解声明一个名为teacherDao的数据层Bean。
TeacherServiceImpl服务层接口实现：

package com.sunbin.test.teacher.service.impl;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.sunbin.test.teacher.dao.TeacherDao;
import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

@Service("teacherService")
public class TeacherServiceImpl implements TeacherService {

	@Autowired
	private TeacherDao teacherDao;

	@SuppressWarnings("rawtypes")
	@Override
	public List list() {
		System.out.println("TeacherServiceImpl.list");
		return teacherDao.list();
	}

	@Override
	public int count() {
		System.out.println("TeacherServiceImpl.count");
		return teacherDao.count();
	}

	@Override
	public void save(Teacher teacher) {
		System.out.println("TeacherServiceImpl.save:" + teacher);
		teacherDao.save(teacher);
	}

	@Override
	public void remove(Teacher teacher) {
		System.out.println("TeacherServiceImpl.remove:" + teacher);
		teacherDao.remove(teacher);
	}

	@Override
	public void update(Teacher teacher) {
		System.out.println("TeacherServiceImpl.update:" + teacher);
		teacherDao.update(teacher);
	}

	@Override
	public Teacher get(Teacher teacher) {
		System.out.println("TeacherServiceImpl.get:" + teacher);
		return teacherDao.get(teacher);
	}

}

该类实现了服务层接口，且@Service("teacherService")注解声明一个名为teacherService的服务层Bean，@Autowired注解将注入teacherDao bean。

4.Contoller
Conroller需要实现设计的7个方法：

package com.sunbin.test.teacher.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.view.json.MappingJackson2JsonView;
import org.springframework.stereotype.Controller;
import org.springframework.beans.factory.annotation.Autowired;

import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

@Controller
@RequestMapping("/teacher")
public class TeacherController {

	@Autowired
	private TeacherService teacherService;

	@RequestMapping("")
	public ModelAndView index(HttpServletRequest arg0, HttpServletResponse arg1)
			throws Exception {
		ModelAndView modelAndView = new ModelAndView("teacher/index");
		return modelAndView;
	}

	@RequestMapping("/list")
	public ModelAndView list(HttpServletRequest arg0, HttpServletResponse arg1)
			throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		modelAndView.addObject("list", teacherService.list());
		return modelAndView;
	}

	@RequestMapping("/count")
	public ModelAndView count(HttpServletRequest arg0, HttpServletResponse arg1)
			throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		modelAndView.addObject("count", teacherService.count());
		return modelAndView;
	}

	@RequestMapping(value = "/save", method = { RequestMethod.POST })
	public ModelAndView save(Teacher teacher, HttpServletRequest arg0,
			HttpServletResponse arg1) throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		teacherService.save(teacher);
		modelAndView.addObject("status", "y");
		return modelAndView;
	}

	@RequestMapping("/remove")
	public ModelAndView remove(Teacher teacher, HttpServletRequest arg0,
			HttpServletResponse arg1) throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		teacherService.remove(teacher);
		modelAndView.addObject("status", "y");
		return modelAndView;
	}

	@RequestMapping(value = "/update", method = { RequestMethod.POST })
	public ModelAndView update(Teacher teacher, HttpServletRequest arg0,
			HttpServletResponse arg1) throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		teacherService.update(teacher);
		modelAndView.addObject("status", "y");
		return modelAndView;
	}

	@RequestMapping("/get")
	public ModelAndView get(Teacher teacher, HttpServletRequest arg0,
			HttpServletResponse arg1) throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		modelAndView.addObject("teacher", teacherService.get(teacher));
		return modelAndView;
	}

}

除了首页使用teacher/index.jsp展示，其他接口返回MappingJackson2JsonView。
save和update配置了method = { RequestMethod.POST }，必须使用POST方法访问。
Controller中的方法可以使用Teacher作为参数，springmvc自动将页面输入组装成pojo传入后台。

5.首页
在WEB-INF/jsp/teacher/下创建index.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<title>teacher</title>
	<script type="text/javascript" src="<%=path %>/resources/js/jquery-3.2.0.js"></script>
	<script type="text/javascript">
		$(document).ready(function(){
			list();
			var ajaxOption = null;
			$("#saveButton").click(function(){
				save();
			});
		});
		function list(){
			$.ajax({
				url:"teacher/list",
				dataType:"json",
				success:function(data){
					$("#listBody").empty();
					$.each(data.list, function(i, item){
						var teacherTr = "<tr><form name='updateForm_"+item.id+"' action='teacher/update' method='POST'>"
							+"<td><input type='hidden' name='id' id='id_"+item.id+"' value='"+item.id+"'/>"+item.id+"</td>"
							+"<td><input type='text' name='name' id='name_"+item.id+"' value='"+item.name+"' /></td>"
							+"<td><input type='text' name='age' id='age_"+item.id+"' value='"+item.age+"' /></td>"
							+"<td><a href='javascript:void(0);' onclick='get("+item.id+");'>get</a> "
							+"<a href='javascript:void(0);' onclick='remove("+item.id+");'>remove</a> "
							+"<input type='submit' value='update' id='updateButton_"+item.id+"' onclick='update("+item.id+");' /></td></tr>";
							//alert(teacherTr);
						$("#listBody").append(teacherTr);
					});
					count();
				}
			});
		}
		function count(){
			$.ajax({
				url:"teacher/count",
				dataType:"json",
				success:function(data){
					$("#count").html(data.count);
				}
			});
		}
		function save(){
			$("#saveButton").attr("disabled", true);
			$.ajax({
				url:"teacher/save",
				type:"POST",
				data:"name="+$("#name").val()+"&"+"age="+$("#age").val(),
				dataType:"json",
				complete:function(){
					$("#saveButton").attr("disabled", false);
				},
				success:function(data){
					alert(data.status);
					list();
				}
			});
		}
		function get(id){
			$.ajax({
				url:"teacher/get",
				data:"id="+id,
				dataType:"json",
				success:function(data){
					var teacherInfo = "id:"+data.teacher.id+"\nname:"+data.teacher.name+"\nage:"+data.teacher.age;
					alert(teacherInfo);
				}
			});
		}
		function remove(id){
			$.ajax({
				url:"teacher/remove",
				data:"id="+id,
				dataType:"json",
				success:function(data){
					alert(data.status);
					list();
				}
			});
		}
		function update(id){
			$("#updateButton_"+id).attr("disabled", true);
			$.ajax({
				url:"teacher/update",
				type:"POST",
				data:"id="+id+"&name="+$("#name_"+id).val()+"&"+"age="+$("#age_"+id).val(),
				dataType:"json",
				complete:function(data){
					$("#updateButton_"+id).attr("disabled", false);
				},
				success:function(data){
					alert(data.status);
					list();
				}
			});
		}
	</script>
</head>
<body>
	save
	<form name="saveForm" action="teacher/save" method="POST">
		name:<input type="text" name="name" id="name" /> 
		
 
		age:<input type="text" name="age" id="age" /> 
		
 
		<input type="button" value="save" id="saveButton" />
	</form>
	count:<span id="count"></span>
	<br/>
	list
	<table border="1">
		<thead>
			<tr>
				<td>id</td>
				<td>name</td>
				<td>age</td>
				<td>操作</td>
			</tr>
		</thead>
		<tbody id="listBody">
		</tbody>
	</table>
</body>
</html>

list()方法GET teacher/list，对返回的teacher集合使用表格展示，并调用count()更改统计数量。
count()方法GET teacher/count，显示返回数量。
save()方法将数据POST至teacher/save保存，成功后刷新表格。
get(id)方法GET teacher/get，弹窗显示单条记录。
remove(id)方法GET teacher/remove，删除单挑记录，成功后刷新表格。
update(id)方法将数据POST至teacher/save更新，成功后刷新表格。

6.测试
重新部署至tomcat，访问 http://localhost:8080/testRest/teacher。
可看到页面内容，并进行增删改查操作


7.springmvc PUT/DELETE调用及参数的坑
如果想要支持http的PUT和DELETE方法，实现RESTFUL接口，只需将Controller方法的注解改为PUT/DELETE：

@RequestMapping(value = "/update", method = { RequestMethod.PUT })

可以使用ajax直接调用PUT请求：

$.ajax({
	url:"teacher/update",
	type:"PUT",
	data:"id="+id+"&name="+$("#name_"+id).val()+"&"+"age="+$("#age_"+id).val(),
...

如果通过表单form调用就没这么简单了。因为html的form只支持GET、POST方法，不能直接发送PUT、DELETE请求。springmvc为了解决这个问题，增加了特殊的过滤器。
在web.xml中增加配置：

<filter>  
    <filter-name>HttpMethodFilter</filter-name>  
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>  
</filter>  
<filter-mapping>  
    <filter-name>HttpMethodFilter</filter-name>  
    <servlet-name>spring</servlet-name>  
</filter-mapping>

配置拦截器处理隐藏参数。HiddenHttpMethodFilter主要源码如下：

public class HiddenHttpMethodFilter extends OncePerRequestFilter {

	/** Default method parameter: {@code _method} */
	public static final String DEFAULT_METHOD_PARAM = "_method";

	private String methodParam = DEFAULT_METHOD_PARAM;


	/**
	 * Set the parameter name to look for HTTP methods.
	 * @see #DEFAULT_METHOD_PARAM
	 */
	public void setMethodParam(String methodParam) {
		Assert.hasText(methodParam, "'methodParam' must not be empty");
		this.methodParam = methodParam;
	}

	@Override
	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		String paramValue = request.getParameter(this.methodParam);
		if ("POST".equals(request.getMethod()) && StringUtils.hasLength(paramValue)) {
			String method = paramValue.toUpperCase(Locale.ENGLISH);
			HttpServletRequest wrapper = new HttpMethodRequestWrapper(request, method);
			filterChain.doFilter(wrapper, response);
		}
		else {
			filterChain.doFilter(request, response);
		}
	}

拦截器会处理POST请求中的_method参数，转换为PUT/DELETE请求。
修改页面form，增加_method参数：

<form action="..." method="POST">
	<input type="hidden" name="_method" value="PUT">
	...
</form>

这种配置虽然能调用到PUT/DELETE，但是参数传递会出现问题，因为springmvc的HiddenHttpMethodFilter不能组装参数成pojo。增加以下拦截器：

<filter>  
    <filter-name>HttpMethodFilter</filter-name>  
    <filter-class>org.springframework.web.filter.HttpPutFormContentFilter</filter-class>  
</filter>  
<filter-mapping>  
    <filter-name>HttpMethodFilter</filter-name>  
    <servlet-name>spring</servlet-name>  
</filter-mapping>

查看HttpPutFormContentFilter拦截器源码，可以看到是对PUT请求的contentbody进行处理。

	@Override
	protected void doFilterInternal(final HttpServletRequest request, HttpServletResponse response,
			FilterChain filterChain) throws ServletException, IOException {

		if (("PUT".equals(request.getMethod()) || "PATCH".equals(request.getMethod())) && isFormContentType(request)) {
			HttpInputMessage inputMessage = new ServletServerHttpRequest(request) {
				@Override
				public InputStream getBody() throws IOException {
					return request.getInputStream();
				}
			};
			MultiValueMap<String, String> formParameters = formConverter.read(null, inputMessage);
			HttpServletRequest wrapper = new HttpPutFormContentRequestWrapper(request, formParameters);
			filterChain.doFilter(wrapper, response);
		}
		else {
			filterChain.doFilter(request, response);
		}
	}

两种方法都可以发送PUT请求调用/update。

该拦截器只能处理PUT的contentbody。
对于DELETE请求，不能获取通过body提交的内容，只能使用参数或者地址变量。
POST content：

function remove(id){
	$.ajax({
		url:"teacher/remove",
		type:"POST",
		data:"id="+id,

修改为DELETE请求参数：

function remove(id){
	$.ajax({
		url:"teacher/remove?id="+id,
		type:"DELETE",

Controller方法：

	@RequestMapping(value = "/remove", method = { RequestMethod.DELETE })
	public ModelAndView remove(Integer id,
			HttpServletRequest arg0, HttpServletResponse arg1) throws Exception {
		ModelAndView modelAndView = new ModelAndView(
				new MappingJackson2JsonView());
		Teacher teacher = new Teacher();
		teacher.setId(id);
		teacherService.remove(teacher);
		modelAndView.addObject("status", "y");
		return modelAndView;
	}

通过ajax发送DELETE请求调用/remove地址成功。
同样可以使用form隐藏参数：

<form action="..." method="POST">
	<input type="hidden" name="_method" value="DELETE">
	...
</form>