springMVC之增删改查

一、核心原理

1. 用于发送请求给server: /home.htm

2. 请求被DispatchServlet拦截到

3. DispatchServlet通过HandleMapping检查url有没有相应的Controller, 假设有则调用Controller

4. Controller開始运行业务逻辑

5. Controller运行完成后, 假设返回字符串, 则ViewResolver将字符串转化成对应的视图对象;

假设返回ModelAndView对象, 该对象本身就包括了视图对象信息.

6. DispatchServlet将视图对象中的数据输出给server.

7. server将数据输出给client.

二、REST风格

1. 查询:
传统:  /user_query?id=123
rest: /user/123
2. 删除:
传统:  /user_delete?id=123
rest: /user/123/delete
3. 更新:
传统:  /user_update?

id=123
rest: /user/123/update
4. 列表:
传统:  /user_list
rest: /user/users

三、增删改查

1. 代码结构

2. web.xml 配置DispatchServlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xmlns="http://java.sun.com/xml/ns/javaee" 
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
         http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
         
  <!-- user须要和配置文件user-servlet.xml名字相应 -->
  <servlet>
  	<servlet-name>user</servlet-name>
  	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  	<load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
  	<servlet-name>user</servlet-name>
  	<url-pattern>/</url-pattern>
  </servlet-mapping>
  
  <!-- 配置过滤器, 设置编码为UTF-8 -->
  <filter>
		<filter-name>CharacterFilter</filter-name>
		<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>UTF-8</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>CharacterFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
</web-app>

 <load-on-startup>1</load-on-startup>是启动顺序。让这个Servlet随Servletp容器一起启动。

 <url-pattern>/</url-pattern> 会拦截全部的请求。

在DispatcherServlet的初始化过程中，框架会在web应用的 WEB-INF目录下寻找名为[servlet-name]-servlet.xml 的配置文件，

生成文件里定义的bean。我们配的是user。所以它会找到user-servlet.xml文件。

3. user-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="http://www.springframework.org/schema/mvc 
		http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.1.xsd">
	
	<!-- spring自己主动扫描的包名 -->
	<context:component-scan base-package="com.zdp"></context:component-scan>
	
	<!-- 使用spring注解 -->
	<mvc:annotation-driven />
	
	<!-- 设置返回url前缀和后缀 -->
	<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
		<property name="prefix" value="/WEB-INF/jsp/"></property>
		<property name="suffix" value=".jsp"></property>
	</bean>
	
	<!-- 指明静态资源位置 -->
	<mvc:resources location="/WEB-INF/resources/" mapping="/resources/**"/>
</beans>

<context:component-scan/> 扫描指定的包中的类上的注解，经常使用的注解有：

@Controller 声明Action组件
@Service  声明Service组件    @Service("userService") 
@Repository 声明Dao组件
@Component 泛指组件, 当不好归类时. 
@RequestMapping("/user") 将url和类绑定 

@RequestParam("name") String username   用于将指定的请求參数赋给方法中的形參, 假设请求參数名称和形參一致, 则不须要这样的写法

@Resource 用于注入，( j2ee提供的 ) 默认按名称装配，@Resource(name="beanName") 
@Autowired 用于注入，(srping提供的) 默认按类型装配 
@Transactional( rollbackFor={Exception.class}) 事务管理
@ResponseBody
@Scope("prototype")   设定bean的作用域

/WEB-INF/resources映射到ResourceHttpRequestHandler进行处理。location指定静态资源的位置.

配置了<mvc:annotation-driven />，spring会自己主动帮我们注冊这个bean,就不需要我们显示的注冊这个bean了。

4. User.java

/**
 * 实体类
 */
public class User {
	private String username;
	private String password;

	public User() {
		
	}

	public User(String username, String password) {
		this.username = username;
		this.password = password;
	}
	
	@NotEmpty(message="用户名不能为空")
	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}
	
	@Size(min=1,max=10,message="密码的长度应该在1和10之间")
	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}

5. UserController.java

@Controller
@RequestMapping("/user")
public class UserController {
	// 使用map模拟数据库 
	private Map<String, User> userMap = new HashMap<String, User>();

	public UserController() {
		userMap.put("zhangsan", new User("zhangsan", "123"));
		userMap.put("lishimin", new User("lishimin", "456"));
	}

	// 获取用户列表 
	// 訪问方法: http://localhost/springmvc_user/user/users
	@RequestMapping(value = "/users", method = RequestMethod.GET)
	public String list(Model model) {
		model.addAttribute("users", userMap);
		return "/user/list";
	}

	// 跳转到加入用户页面(get请求)
	// 訪问方法: http://localhost/springmvc_user/user/add
	@RequestMapping(value = "/add", method = RequestMethod.GET)
	public String add(@ModelAttribute("user") User user) {
		return "user/add";
	}

	// 详细的加入用户处理方法(post请求) 
	// 注意: BindingResult必须在User之后, 中间不能有其它的參数
	@RequestMapping(value = "/add", method = RequestMethod.POST)
	public String add(@Validated User user, BindingResult br) throws IOException { // @Validated: 对User数据进行校验
		if (br.hasErrors()) {
			return "user/add"; // 假设有错误, 则直接跳转到add加入用户页面
		}
		userMap.put(user.getUsername(), user);
		return "redirect:/user/users"; // 重定向到用户列表页面
	}
	
	// 查看用户信息
	// 訪问方法: http://localhost/springmvc_user/user/zhangsan
	@RequestMapping(value="/{username}", method=RequestMethod.GET)
	public String show(@PathVariable String username, Model model) { // @PathVariable: 路径里面的值作为參数
		model.addAttribute(userMap.get(username)); 
		return "user/show";
	}
	
	// 跳转到改动用户信息页面
	// 訪问方法: http://localhost/springmvc_user/zhangsan/update
	@RequestMapping(value="/{username}/update", method=RequestMethod.GET) 
	public String update(@PathVariable String username, Model model) { // @PathVariable: 路径里面的值作为參数
		model.addAttribute(userMap.get(username)); // 等同: model.addAttribute("user", userMap.get(username));
		return "user/update";
	}
	
	// 详细的改动用户处理方法(post请求) 
	// 注意: BindingResult必须在User之后, 中间不能有其它的參数
	@RequestMapping(value="/{username}/update", method=RequestMethod.POST)
	public String update(@PathVariable String username, @Validated User user, BindingResult br) {
		if(br.hasErrors()) {
			return "user/update"; // 假设有错误, 则直接跳转到update改动用户页面
		}
		userMap.remove(username);
		userMap.put(user.getUsername(), user);
		return "redirect:/user/users";
	}
	
	// 删除用户信息
	// 訪问方法: http://localhost/springmvc_user/zhangsan/delete
	@RequestMapping(value="/{username}/delete",method=RequestMethod.GET)
	public String delete(@PathVariable String username) {
		userMap.remove(username);
		return "redirect:/user/users";
	}
	
}

一般建议返回字符串, 但我们也能够返回ModelMap、ModelAndView、map、List、Set、Object、无返回值。 

返回字符串: 依据返回值找相应的显示页面。路径规则为：prefix前缀 + 返回值 + suffix后缀组成

6. jsp pages

① list.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!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>用户列表 </title>
<!-- 引入静态文件, 须要在user-servlet.xml配置映射关系 -->
<link rel="stylesheet" href="<%=request.getContextPath()%>/resources/css/main.css" type="text/css">
</head>
<body>
<a href="add">加入</a>
<br/>
	<c:forEach items="${users}" var="usermap">
		<a href="${usermap.value.username}">${usermap.value.username}</a>
		-- <a href="${usermap.value.username}/update">改动</a>
		-- <a href="${usermap.value.username}/delete">删除</a><br/>
	</c:forEach>
</body>
</html>

② add.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="sf" uri="http://www.springframework.org/tags/form" %>
<!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>加入用户</title>
</head>
<body>
<!-- 如没写action, 也会提交给add(匹配文件名称) -->
<sf:form method="post" modelAttribute="user" action="add">
	Username:<sf:input path="username"/><sf:errors path="username"/><br/>
	Password:<sf:password path="password"/><sf:errors path="password"/><br/>
	<input type="submit" value="加入用户"/>
</sf:form>
</body>
</html>

③ show.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="sf" uri="http://www.springframework.org/tags/form" %>
<!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>用户具体信息</title>
</head>
<body>
	Username:${user.username}<br/>
	Password:${user.password}<br/>
</body>
</html>

④ update.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="sf" uri="http://www.springframework.org/tags/form" %>
<!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>改动用户</title>
</head>
<body>
<!-- 如没写action, 也会提交给update(匹配文件名称) -->
<sf:form method="post" modelAttribute="user" action="update">
	Username:<sf:input path="username"/><sf:errors path="username"/><br/>
	Password:<sf:password path="password"/><sf:errors path="password"/><br/>
	<input type="submit" value="改动用户"/>
</sf:form>
</body>
</html>