spring-06 springmvc设计思想与体系结构

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1.servlet 与jsp 执行过程

流程说明：

1. 请求Servlet
2. 处理业务逻辑
3. 设置业务Model
4. forward jsp Servlet
5. jsp Servlet 解析封装html 返回

2.spring mvc 执行

spring mvc本质上还是在使用Servlet处理，并在其基础上进行了封装简化了开发流程，提高易用性、并使用程序逻辑结构变得更清晰

• 基于注解的URL映谢
• http表单参数转换
• 全局统一异常处理
• 拦截器的实现

2.1 spring mvc 执行流程

2.2 spring mvc 体系结构

• HandlerMapping:
  url与控制器的映谢
• HandlerAdapter:
  控制器执行适配器
• ViewResolver:
  视图仓库
• view:
  具体解析视图
• HandlerExceptionResolver:
  异常捕捕捉器
• HandlerInterceptor:
  拦截器

2.3 实现简单spring mvc

2.3.1 项目依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>spring-study</artifactId>
        <groupId>com.myx</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <packaging>jar</packaging>
    <artifactId>spring-mvc</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </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>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.mortbay.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <version>7.4.5.v20110725</version>
                <configuration>
                    <webApp>
                        <contextPath>/</contextPath>
                    </webApp>
                    <scanIntervalSeconds>3</scanIntervalSeconds>
                    <scanTargetPatterns>
                        <scanTargetPattern>
                            <directory>src/main/webapp</directory>
                            <includes>
                                <include>**/*.xml</include>
                            </includes>
                        </scanTargetPattern>
                    </scanTargetPatterns>
                    <connectors>
                        <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
                            <port>8081</port>
                            <maxIdleTime>400000</maxIdleTime>
                        </connector>
                    </connectors>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

2.3.2 web.xml

<?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" xmlns:web="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_3_0.xsd"
         id="WebApp_ID" version="3.0">
    <!-- root ioc -->
    <display-name>spring-mvc</display-name>
    <servlet>
        <servlet-name>dispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>
                classpath:/spring-mvc.xml
            </param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
        <welcome-file>/index.html</welcome-file>
    </welcome-file-list>

</web-app>

2.3.3 spring-mvc.xml

<?xml version="1.0" encoding="GBK"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!--控制器-->
    <bean id="simpleController" class="com.myx.spring.controller.SimpleController"></bean>

    <!-- url映谢器-->
    <bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="urlMap">
            <props>
                <prop key="/user.do">simpleController</prop>
            </props>
        </property>
    </bean>

    <!-- 执行适配器-->
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"></bean>

    <!-- 视图仓库 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/page/"/>
        <property name="suffix" value=".jsp"/>
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
    </bean>
</beans>

2.3.4 创建controller

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

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

/**
 * 描述:简单路由映射实现mvc
 * @author: myx
 * @date: 2019/1/14
 * Copyright © 2018-hotpot. All rights reserved.
 */
public class SimpleController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mv = new ModelAndView("userView");
        mv.addObject("name", "myx is good man");
        return mv;
    }
}

2.3.5 运行jeety

2.4 体系结构UML

3.mvc 执行流程解析

3.1 mvc 各组件执行流程

3.2 HandlerMapping 详解

其为mvc 中url路径与Control对像的映射，DispatcherServlet 就是基于此组件来寻找对应的Control，如果找不到就会报Not Found mapping 的异常。

3.2.1 HandlerMapping 接口方法

3.2.2 HandlerMapping 接口结构

目前主流的三种mapping:

• BeanNameUrlHandlerMapping: 基于ioc name 中已 “/” 开头的Bean时行 注册至映谢.
• SimpleUrlHandlerMapping：基于手动配置 url 与control 映谢
• RequestMappingHandlerMapping：基于@RequestMapping注解配置对应映谢

3.2.2.1 BeanNameUrlHandlerMapping 使用(4.1 以后不支持)

<!--简单控制器-->
<bean id="/bean.do" class="com.myx.spring.controller.BeanNameController"></bean>

import org.springframework.web.HttpRequestHandler;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * 描述:BeanNameUrlHandlerMapping 测试
 * @author: myx
 * @date: 2019/1/14
 * Copyright © 2018-hotpot. All rights reserved.
 */
public class BeanNameController implements HttpRequestHandler {
    @Override
    public void handleRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.getWriter().println("myx is good man");
    }
}

3.3 HandlerAdapter详解

这里spring mvc 采用适配器模式来适配调用指定Handler，根据Handler的不同种类采用不同的Adapter,其Handler与 HandlerAdapter 对应关系如下:

Handler类别	对应适配器	描述
Controller	SimpleControllerHandlerAdapter	标准控制器，返回ModelAndView
HttpRequestHandler	HttpRequestHandlerAdapter	业务自行处理 请求，不需要通过modelAndView 转到视图
Servlet	SimpleServletHandlerAdapter	基于标准的servlet 处理
HandlerMethod	RequestMappingHandlerAdapter	基于@requestMapping对应方法处理

3.3.1 HandlerAdapter 接口方法

3.3.2 HandlerAdapter 接口结构图

3.3.3 基于Servlet处理SimpleServletHandlerAdapter(4.1 以后不支持)

<!-- 配置控制器 -->
<bean id="/hello.do" class="com.myx.spring.controller.HelloServlet"/>

<!-- 配置适配器 -->
<bean class="org.springframework.web.servlet.handler.SimpleServletHandlerAdapter"/>

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        resp.getWriter().println("hello luban ");
    }
}

3.4 ViewResolver 与View 详解

找到应的Adapter 之后就会基于适配器调用业务处理，处理完之后业务方会返回一个ModelAndView ，在去查找对应的视图进行处理。其在org.springframework.web.servlet.DispatcherServlet#resolveViewName() 中遍历 viewResolvers 列表查找，如果找不到就会报一个 Could not resolve view with name 异常。

在下一步就是基于ViewResolver.resolveViewName() 获取对应View来解析生成Html并返回 。对应VIEW结构如下：

至此整个正向流程就已经走完了，如果此时程序处理异常 MVC 该如何处理呢？

3.5 HandlerExceptionResolver详解

该组件用于指示 当出现异常时 mvc 该如何处理。 dispatcherServlet 会调用org.springframework.web.servlet.DispatcherServlet#processHandlerException() 方法，遍历 handlerExceptionResolvers 处理异常，处理完成之后返回errorView 跳转到异常视图。

3.5.1 使用

<bean class="com.myx.spring.controller.SimpleExceptionHandle"/>


import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 描述:异常
 * @author: myx
 * @date: 2019/1/14
 * Copyright © 2018-hotpot. All rights reserved.
 */
public class SimpleExceptionHandle implements HandlerExceptionResolver {
    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        return new ModelAndView("error");
    }
}

3.6 HandlerInterceptor 详解

除了上述组件之外 spring 中还引入了 我Interceptor 拦截器 机制，类似于Filter。

3.6.1 演示

<!--配置interceptor 组件-->
<bean class="com.myx.spring.controller.SimpleHandlerInterceptor"></bean>

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 描述:拦截器
 * @author: myx
 * @date: 2019/1/14
 * Copyright © 2018-hotpot. All rights reserved.
 */
public class SimpleHandlerInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion");
    }
}

其实现机制是基于 HandlerExecutionChain 分别在 doDispatch 方法中执行以下方法：

• preHandle ：业务处理前执行
• postHandle：业务处理后（异常则不执行）
• afterCompletion：视图处理后

具体逻辑源码参见：org.springframework.web.servlet.DispatcherServlet#doDispatch 方法。

4.注解配置

4.1 实现

<?xml version="1.0" encoding="GBK"?>
<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/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/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <context:component-scan base-package="com.myx.spring.controller" />
    <!-- 注解驱动 -->
    <mvc:annotation-driven/>
    <!-- 视图仓库 -->
    <bean  class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/page/" />
        <property name="suffix" value=".jsp" />
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
    </bean>
</beans>

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

/**
 * 描述:注解实现
 * @author: myx
 * @date: 2019/1/14
 * Copyright © 2018-hotpot. All rights reserved.
 */
@Controller
public class SimpleController{
    /**
     * 注解方法
     * @return
     */
    @RequestMapping("/hello.do")
    public ModelAndView hello() {
        ModelAndView mv = new ModelAndView("userView");
        mv.addObject("name", "myx 注解");
        return mv;
    }
}

4.2 为什么基于 mvc:annotation-driven/ 配置就能实现mvc 的整个配置了，之前所提到的 handlerMapping 、与handlerAdapter 组件都不适用了？

只要查看以类的源就可以知晓其中原因：

• 认识 NamespaceHandler 接口
• 查看 MvcNamespaceHandler
• 查看AnnotationDrivenBeanDefinitionParser

结论：
在<mvc:annotation-driven /> 对应的解析器，自动向ioc 里面注册了两个BeanDefinition。分别是：RequestMappingHandlerMapping与BeanNameUrlHandlerMapping