Spring MVC開發流程詳解

其實開發Spring MVC流程並不困難。開發Spring MVC程序，需要掌握Spring MVC的組件和流程，所以在開發過程中也會貫穿着Spring MVC的運行流程。
如果不清楚Spring MVC的運行流程，可以參考博客：Spring MVC運行流程淺析

在目前的開發過程中，大部分都會採用註解的開發方式，主要是以一個註解@Controller標註，一般只需要通過掃描配置，就能夠將其掃描出來，只是往往還要結合註解@RequestMapping去配置它。@RequestMapping可以配置在類和方法之上，它的作用是指定URI和哪個類（或者方法）作爲一個處理請求的處理器，爲了更加靈活，Spring MVC還定義了處理器的攔截器，當啓動Spring MVC的時候，Spring MVC就會去解析@Controller中的@RequestMapping的配置，再結合所配置的攔截器，這樣它就會組成多個攔截器和一個控制器得形式，存放到一個HandlerMapping中去。當請求來到服務器，首先是通過請求信息找到對應的HandlerMapping，進而可以找到對應的攔截器和處理器，這樣就能夠運行對應的控制器和攔截器。

配置@RequestMapping

	@RequestMapping(value = "/getRole",method= RequestMethod.GET)
    public ModelAndView getRole(@RequestParam("id") Long id){
        Role role=roleService.getRole(id);
        ModelAndView mv=new ModelAndView();
        mv.addObject("role",role);
        //指定視圖類型
        mv.setViewName("roleDetails");
        return mv;
    }

一般配置@RequestMapping最常用到的是請求路徑和請求類型，其他的大部分作爲限定項，根據需要進行配置。

控制器的開發

控制器開發是Spring MVC的核心內容，其步驟一般分爲三步：

• 獲取請求參數。
• 處理業務邏輯。
• 綁定模型和視圖。

獲取請求參數：
在Spring MVC中接收參數的方法很多，比如如果要獲取一個HTTP請求的參數——id，它是一個長整型，那麼可以使用註解@RequestParam來獲取它。

public ModelAndView getRole(@RequestParam("id") Long id)

通過@RequestParam註解，Spring MVC 就知道從HTTP請求中獲取參數，即使用類似於如下的邏輯進行轉換：

String idStr=request.getParameter("id");
Long id=Long.parseLong(idStr);

下面我用一個簡單的實例來展示一下Spring MVC開發流程以及參數的獲取。

實例文件框架：

RoleController.java

package com.ssm.example1.controller;

import com.ssm.example1.pojo.Role;
import com.ssm.example1.service.RoleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/role")
public class RoleController {
    //注入角色服務類
    @Autowired
    private RoleService roleService=null;

    @RequestMapping(value = "/getRole",method= RequestMethod.GET)
    public ModelAndView getRole(@RequestParam("id") Long id){
        Role role=roleService.getRole(id);
        ModelAndView mv=new ModelAndView();
        mv.addObject("role",role);
        //指定視圖類型
        mv.setViewName("roleDetails");
        return mv;
    }
}

RoleMapper.java

package com.ssm.example1.mapper;

import com.ssm.example1.pojo.Role;
import org.springframework.stereotype.Repository;

@Repository
public interface RoleMapper {
    public int insertRole(Role role);
    public Role getRole(Long id);
}

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <mappers>
        <mapper resource="com/ssm/example1/sqlMapper/RoleMapper.xml" />
    </mappers>
</configuration>

Role.java

package com.ssm.example1.pojo;

public class Role {
    private Long id;
    private String roleName;
    private String note;

    public Long getId() {
        return id;
    }

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

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    public Role(){}
}

RoleService.java

package com.ssm.example1.service;


import com.ssm.example1.pojo.Role;

public interface RoleService {
    public int insertRole(Role role);
    public Role getRole(Long id);
}

RoleServiceImpl.java

package com.ssm.example1.service.impl;


import com.ssm.example1.mapper.RoleMapper;
import com.ssm.example1.pojo.Role;
import com.ssm.example1.service.RoleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Isolation;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@Service
public class RoleServiceImpl implements RoleService {
    @Autowired
    private RoleMapper roleMapper=null;

    @Override
    @Transactional(propagation = Propagation.REQUIRES_NEW,isolation = Isolation.READ_COMMITTED)
    public int insertRole(Role role) {
        return roleMapper.insertRole(role);
    }

    @Override
    @Transactional(propagation = Propagation.REQUIRES_NEW,isolation = Isolation.READ_COMMITTED)
    public Role getRole(Long id) {
        return roleMapper.getRole(id);
    }
}

RoleMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.ssm.example1.mapper.RoleMapper">
        <resultMap id="roleMap" type="com.ssm.example1.pojo.Role">
            <id property="id" column="id" />
            <result property="roleName" column="role_name" />
            <result property="note" column="note" />
        </resultMap>

        <insert id="insertRole" parameterType="com.ssm.example1.pojo.Role">
            insert into role(role_name,note) values (#{roleName},#{note})
        </insert>

        <select id="getRole" resultMap="roleMap">
            select id,role_name,note from role where id=#{id}
        </select>
    </mapper>
    

roleDetails.jsp

<%--
  Created by IntelliJ IDEA.
  User: win
  Date: 2020/4/26
  Time: 14:52
  To change this template use File | Settings | File Templates.
--%>
<%@ page pageEncoding="gbk" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>out標籤的使用</title>
</head>
<body>
</body>
<center>
    <table border="1">
        <tr>
            <td>
                標籤
            </td>
            <td>
                值
            </td>
        </tr>
        <tr>
            <td>
                角色編號
            </td>
            <td>
                <c:out value="${role.id}"></c:out>
            </td>
        </tr>
        <tr>
            <td>
                角色名稱
            </td>
            <td>
                <c:out value="${role.roleName}"></c:out>
            </td>
        </tr>
        <tr>
            <td>
                角色備註
            </td>
            <td>
                <c:out value="${role.note}"></c:out>
            </td>
        </tr>
    </table>
</center>
</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!-- 配置Spring IoC配置文件路徑-->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>
    <!-- 配置ContextLoaderListener用以初始化Spring IoC容器-->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!--配置DispatcherServlet -->
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>2</load-on-startup>
    </servlet>
    <!-- Servlet 攔截配置-->
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>
</web-app>

applicationContext

<?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"
       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">

    <!-- 使用註解驅動-->
    <context:annotation-config />

    <!-- 數據庫連接池-->
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/ssm" />
        <property name="username" value="root" />
        <property name="password" value="123456" />
        <property name="maxActive" value="255" />
        <property name="minIdle" value="5" />
        <property name="maxIdle" value="10000" />
    </bean>

    <!--集成mybaties -->
    <bean id="SqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="configLocation" value="classpath:com/ssm/example1/mybatis/mybatis-config.xml" />
    </bean>

    <!-- 配置數據源事務管理器-->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>

    <!-- 採用自動掃描方式創建mapper bean-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.ssm.example1" />
        <property name="sqlSessionFactory" ref="SqlSessionFactory" />
        <property name="annotationClass" value="org.springframework.stereotype.Repository" />
    </bean>
</beans>

dispatcher-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:p="http://www.springframework.org/schema/p"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       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/tx
       http://www.springframework.org/schema/tx/spring-tx.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!-- 使用註解驅動-->
    <mvc:annotation-driven />
    <!-- 定義掃描裝載的包-->
    <context:component-scan base-package="com.*" />
    <!-- 定義視圖解析器-->
    <!-- 找到Web工程/WEB-INF/JSP文件夾，且文件結尾爲jsp的文件作爲映射-->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          p:prefix="/WEB-INF/jsp/" p:suffix=".jsp" />

</beans>

然後通過tomcat運行，輸入網址：http://localhost:8080/role/getRole.do?id=1

運行結果