spring-06 springmvc设计思想与体系结构
文章目录
- 1.servlet 与jsp 执行过程
- 2.spring mvc 执行
- 3.mvc 执行流程解析
- 3.1 mvc 各组件执行流程
- 3.2 HandlerMapping 详解
- 3.3 HandlerAdapter详解
- 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)
- 3.4 ViewResolver 与View 详解
- 3.5 HandlerExceptionResolver详解
- 3.6 HandlerInterceptor 详解
- 4.注解配置
1.servlet 与jsp 执行过程
流程说明:
- 请求Servlet
- 处理业务逻辑
- 设置业务Model
- forward jsp Servlet
- 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