Spring MVC浅入浅出——不吹牛逼不装逼

泰斗贤若如

发布于 2019-08-09 18:58:46

5400

发布于 2019-08-09 18:58:46

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）。

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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";

    }

}