Spring MVC浅入浅出——不吹牛逼不装逼
前言
上文书说了Spring相关的知识,对Spring来了个浅入浅出,大家应该了解到,Spring在三层架构中主做Service层,那还有Web层,也就是Controller层,这个就由SpringMVC来解决了。SpringMVC是Web层的一个框架,它是Spring的组成部分,可以先看看下面这张图:
SpringMVC工作原理
MVC模式在之前我已经写过博客了《Web开发模式》,学SpringMVC之前有必要先看一下MVC模式。
SpringMVC框架主要由DispatcherServlet、处理器映射、控制器、视图解析器、视图组成,其工作流程如下:
- 客户端请求提交到DispatcherServlet;
- 由DispatcherServlet控制器寻找一个或多个HandlerMapping,找到处理请求的Controller;
- DispatcherServlet将请求提交到Controller;
- Controller调用业务逻辑处理后返回ModelAndView;
- DispatcherServlet寻找一个或多个ViewResolver视图解析器,找到ModelAndView指定的视图;
- 视图负责将结果显示到客户端。
在SpringMVC工作流程中包含4个SpringMVC接口,即DispatcherServlet、HandlerMapping、Controller和ViewResolver。SpringMVC所有的请求都经过DispatcherServlet来统一分发,在DispatcherServlet将请求分发给Controller之前需要借助SpringMVC提供的HandlerMapping定位到具体的Controller。
HandlerMapping接口负责完成客户请求到Controller映射。
Controller接口将处理用户请求,这和Java 中Servlet扮演的角色是一致的。一旦Controller处理完用户请求,将返回ModelAndView对象给DispatcherServlet前端控制器,ModelAndView中包含了模型(Model)和视图(View)。
从宏观角度考虑,DispatcherServlet是整个Web应用的控制器;从微观考虑,Controller是单个Http请求处理过程中的控制器,而ModelAndView是Http请求过程中返回的模型(Model)和视图(View)。
ViewResolver接口(视图解析器)在Web应用中负责查找View对象,从而将相应结果渲染给客户。
基于注解的控制器
在使用Web应用开发时Controller是Web应用的核心,Controller实现类包含了对用户请求的处理逻辑,是用户请求和业务逻辑之间的桥梁就,是SpringMVC框架的核心部分,负责具体的业务逻辑处理。传统风格的控制器是实现Controller接口的类。传统风格的控制器不仅需要在配置文件中部署映射,而且只能编写一个处理方法,不够灵活。
基于注解的控制器具有以下两个优点:
- 在基于注解的控制器类中可以编写多个处理方法,进而可以处理多个请求(动作),这就允许将相关的操作编写在同一个控制器类中,从而减少控制器类的数量,方便以后的维护。
- 基于注解的控制器不需要在配置文件中部署映射,仅需要使用RequestMapping注释类型注解一个方法进行请求处理。
在SpringMVC中使用扫描机制找到应用中所有基于注解的控制器类,所以,为了让控制器类被SpringMVC框架扫描到,需要在配置文件中声明spring-context,并使用<context:component-scan/>元素指定控制器类的基本包(确保所有控制类都在基本包及其子包下)。示例如下:
<?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:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="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.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
">
<!--配置注解要扫描的包-->
<context:component-scan base-package="com.my"></context:component-scan>
<!--配置视图解析器-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!--配置前缀-->
<property name="prefix" value="/"></property>
<!--配置后缀-->
<property name="suffix" value=".jsp"></property>
</bean>
</beans>
说这么多,用实例说话吧
实例解说
Pom.xml
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
<!--spring核心依赖-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
</dependencies>
spring-config.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:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="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.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
">
<!--配置注解要扫描的包-->
<context:component-scan base-package="com.my"></context:component-scan>
<mvc:annotation-driven></mvc:annotation-driven>
<!--配置spring-jdbcTemplate-->
<!--配置数据源-->
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<!--MySQL数据库驱动-->
<property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
<!--连接数据库的URL-->
<property name="url" value="jdbc:mysql://localhost:3306/bbb?useUnicode=true&characterEncoding=UTF-8"></property>
<!--连接数据库的用户名-->
<property name="username" value="root"></property>
<!--连接数据库的密码-->
<property name="password" value="root"></property>
</bean>
<!--配置JDBC模板-->
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"></property>
</bean>
<!--配置事务-->
<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"></property>
</bean>
<!--注册事务注解驱动-->
<tx:annotation-driven transaction-manager="txManager"></tx:annotation-driven>
<!--配置视图解析器-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!--配置前缀-->
<property name="prefix" value="/"></property>
<!--配置后缀-->
<property name="suffix" value=".jsp"></property>
</bean>
</beans>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app>
<!--部署DispatcherServlet-->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--表示容器在启动时立即加载servlet-->
<load-on-startup>1</load-on-startup>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-config.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<!--处理所有URL-->
<url-pattern>/</url-pattern>
</servlet-mapping>
<!--处理中文乱码-->
<filter>
<filter-name>encodingFilter</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>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!--设置访问静态资源-->
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.css</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.js</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.jpg</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.png</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.gif</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.mp3</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.mp4</url-pattern>
</servlet-mapping>
</web-app>
User
package com.my.pojo;
public class User {
private int id;
private String username;
private String password;
public User() {
}
public User(int id, String username, String password) {
this.id = id;
this.username = username;
this.password = password;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
UserDao
package com.my.dao;
public interface UserDao {
public void add();
public void delete();
public void update();
public void query();
}
UserDaoImpl
package com.my.dao.impl;
import com.my.dao.UserDao;
import com.my.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository("userDao")
public class UserDaoImpl implements UserDao {
@Autowired
//使用配置文件中的JDBC模板
private JdbcTemplate jdbcTemplate;
@Override
public void add() {
String insertSql = "insert into user values(null,?,?)";
for (int i=0;i<15;i++){
Object parem1[] = {"成功","123456"};
jdbcTemplate.update(insertSql,parem1);
}
System.out.println("UserDao中的添加功能实现了");
}
@Override
public void delete() {
String deleteSql = "delete from user where id=?";
Object parem2[] = {5};
jdbcTemplate.update(deleteSql,parem2);
System.out.println("UserDao中的删除功能实现了");
}
@Override
public void update() {
String updateSql = "update user set username=? , password=? where id =?";
Object parem3[] = {"修改","654321",3};
jdbcTemplate.update(updateSql,parem3);
System.out.println("UserDao中的修改功能实现了");
}
@Override
public void query() {
String selectSql = "select * from user";
RowMapper<User> rowMapper = new BeanPropertyRowMapper<User>(User.class);
List<User> list = jdbcTemplate.query(selectSql,rowMapper,null);
System.out.println("UserDao中的查询功能实现了");
for (User user : list){
System.out.println(user);
}
}
}
UserService
package com.my.service;
public interface UserService {
public void add();
public void delete();
public void update();
public void query();
}
UserServiceImpl
package com.my.service.impl;
import com.my.dao.UserDao;
import com.my.dao.impl.UserDaoImpl;
import com.my.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserDao userDao ;
@Override
public void add() {
userDao.add();
}
@Override
public void delete() {
userDao.delete();
}
@Override
public void update() {
userDao.update();
}
@Override
public void query() {
userDao.query();
}
}
UserController
package com.my.controller;
import com.my.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/user")
public class UserController {
@Autowired
private UserService userService;
@RequestMapping("/add")
public String add(){
userService.add();
return "index";
}
@RequestMapping("/delete")
public String delete(){
userService.delete();
return "index";
}
@RequestMapping("/update")
public String update(){
userService.update();
return "index";
}
@RequestMapping("/query")
public String query(){
userService.query();
return "index";
}
}
测试结果
结束
欲看下文如何,请看下回讲解。
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