SpringMVC（5）

于 2021-04-04 20:13:26 发布
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分类专栏： SpringMVC Java EE Spring 文章标签： java spring
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SpringMVC（5）

1.案例一：解决中文乱码问题（character-encoding-filter）

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pom.xml

<?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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.cskaoyan</groupId>
    <artifactId>demo1-character-encoding-filter</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.2.10.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>3.0-alpha-1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.18</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.11.3</version>
        </dependency>
    </dependencies>


</project>

BaseRespVo

package com.cskaoyan.bean;

import lombok.Data;

@Data
public class BaseRespVo<T> {
    T data;
    String message;
    int errno;

    public static BaseRespVo ok(){
        BaseRespVo baseRespVo = new BaseRespVo();
        baseRespVo.setMessage("成功");
        baseRespVo.setErrno(0);
        return baseRespVo;
    }

    public static BaseRespVo ok(Object data){
        BaseRespVo baseRespVo = new BaseRespVo();
        baseRespVo.setData(data);
        baseRespVo.setMessage("成功");
        baseRespVo.setErrno(0);
        return baseRespVo;
    }
}

User

package com.cskaoyan.bean;

import lombok.Data;

@Data
public class User {
    String username;
    String password;
}

UserController

package com.cskaoyan.controller;

import com.cskaoyan.bean.BaseRespVo;
import com.cskaoyan.bean.User;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @RequestMapping("login")
    public BaseRespVo login(User user){
        return BaseRespVo.ok(user);
    }
}

application.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:aop="http://www.springframework.org/schema/aop"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:component-scan base-package="com.cskaoyan"/>
    <mvc:annotation-driven/>


</beans>

index.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<form action="login" method="post">
    用户：<input type="text" name="username"><br>
    密码：<input type="text" name="password"><br>
    <input type="submit">
</form>
</body>
</html>

web.xml

1 CharacterEncodingFilter
CharacterEncodingFilter的doFilter → doFilterInternal方法 → setCharacterEncoding

setEncoding → utf-8
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<?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">
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <!--调用set方法-->
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    
    <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:application.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

结果：
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2.案例二-SpringMVC中的拦截器（handler-interceptor）

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2.1 原理

功能类似于filter

通过HandlerMapping会生成一个HandlerExecutionChain（执行链） → List Handler

底层代码;
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在执行到handler之前就会按照HandlerInterceptorList中的HandlerInterceptor的顺序去执行里面的方法

HandlerInterceptor中的方法

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2.1.1 preHandle（预处理）

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返回值为boolean → 返回值决定是否能继续流程

2.1.2 postHandle（后处理）

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handler方法执行完响应的ModelAndView，如果响应的是json，那么这里的modelAndView就是null，可以对ModelAndView做额外的处理

2.1.3 afterCompletion

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Exception是handler方法抛出的异常
handler方法抛出异常，仍有可能执行到afterCompletion

如果当前的HandlerInterceptor的preHandle方法返回值结果为true，一定可以执行到对应的afterCompletion

pom.xml(和上面一样)

HelloController

//@RestController("hello")//组件id
@Controller
@RequestMapping("hello")//窄化请求
public class HelloController {

    //localhost:8080/hello/world
    @RequestMapping("world")
    @ResponseBody
    public String hello(){//因为有@RestController,所以响应的是字符串而不是视图名
        System.out.println("hello world");
        return "helloworld";
    }
    //localhost:8080/hello/world2
    @RequestMapping("world2")
    public String hello2(){//因为有@RestController,所以响应的是字符串而不是视图名
        System.out.println("hello world");
        //return "helloworld"; //hello/helloworld
        return "/helloworld.jsp"; //helloworld.jsp
    }
}

CustomHandlerInterceptor

@Component
public class CustomHandlerInterceptor 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 {
        if (modelAndView != null){
            modelAndView.setViewName("/postHandle.jsp");

        }
        System.out.println("postHandle");
    }

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

application.xml

2.2HandlerInterceptor的作用范围

2.2.1 全局

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2.2.2 局部

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<?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:aop="http://www.springframework.org/schema/aop"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:component-scan base-package="com.cskaoyan"/>
    <mvc:annotation-driven/>

    <!--mvc:interceptors-->
    <mvc:interceptors>
        <!--
            如果使用bean标签或ref标签的话，作用范围是全局
            全局：DispatcherServlet作用范围下的全局
        -->
        <!--<ref bean="customHandlerInterceptor"/>-->
        <!--<bean class="com.cskaoyan.interceptor.CustomHandlerInterceptor"/>-->
        <mvc:interceptor>
            <!--
                /hello → hello这个请求
                /hello* → helloxxx请求
                /hello/* → hello/xxx请求
                /hello/** → hello以及hello的所有多级请求 /hello/aaa/bbb/ccc
            -->
            <mvc:mapping path="/hello/**"/>
            <ref bean="customHandlerInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

</beans>

helloworld.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>Hello world页面</h1>
</body>
</html>

postHand.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>之后处理了</h1>
</body>
</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">
    <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:application.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

结果：
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在这里插入图片描述

3.案例三（many-handler-interceptor）

3.1多个interceptor的执行顺序

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（1）如果其中的某个preHandle返回值为false，则中断流程；
（2）如果当前interceptor的preHandle返回值为true，一定可以执行到对应的afterCompletion

在这里插入图片描述
示例:

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pom.xml(和案例2一样)

HelloController(和案例2一样)

HandlerInterceptor1

@Component
public class HandlerInterceptor1 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle1");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle1");

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion1");

    }
}

HandlerInterceptor2

@Component
public class HandlerInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle2");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle2");

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion2");

    }
}

HandlerInterceptor3

@Component
public class HandlerInterceptor3 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle3");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle3");

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion3");

    }
}

application.xml
在这里插入图片描述

<?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:aop="http://www.springframework.org/schema/aop"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:component-scan base-package="com.cskaoyan"/>
    <mvc:annotation-driven/>

    <mvc:interceptors>
        <!--顺序和书写顺序相关-->
        <ref bean="handlerInterceptor1"/>
        <ref bean="handlerInterceptor2"/>
        <ref bean="handlerInterceptor3"/>
    </mvc:interceptors>

</beans>

web.xml(和案例2一样)
结果：
在这里插入图片描述
在这里插入图片描述
在这里插入图片描述
在这里插入图片描述

4.案例四（handler-exception-resolver）

在这里插入图片描述

4.1 异常处理

在这里插入图片描述

4.1.1 HandlerExceptionResolver（全局处理）

只要异常抛出就进入到该处理器，通用
只需要注册到容器中，该组件就生效

pom.xml不变

HelloController

@Controller
public class HelloController {

    @RequestMapping("hello/{username}")
    public String hello(@PathVariable("username")String username) throws SensitiveWordException {
        if ("dawa".equals(username)){
            //int i = 1 / 0;
        } else if ("erwa".equals(username) || "sanwa".equals(username)) {
            throw new SensitiveWordException(username, "小金刚");
        }
        return "/hello.jsp";
    }
}

CustomHandlerExceptionResolver

  • 只需要增加@Component则生效（只需要注册到容器中）
  • handler方法向上抛出异常，则会执行到resovleException方法

在这里插入图片描述


@Component
public class CustomHandlerExceptionResolver implements HandlerExceptionResolver {
    /**
     * @param handler → Handler方法
     * @param exception → 向上抛出的异常对应
     * @return ModelAndView → 最后处理后的ModelAndView
     */
    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response,
                                         Object handler, Exception exception) {
        ModelAndView modelAndView = new ModelAndView("/WEB-INF/exception.jsp");

        //根据抛出的异常不同，做个性化的处理 → 异常类型的不同
        if (exception instanceof SensitiveWordException) {
            SensitiveWordException sensitiveWordException = (SensitiveWordException) exception;
            String word = sensitiveWordException.getWord();//从handler方法中抛出的异常对象封装的
            String message = sensitiveWordException.getMessage();
            modelAndView.setViewName("/WEB-INF/sensitive.jsp");
            modelAndView.addObject("word", word);
            modelAndView.addObject("messagez", message);
        }

        return modelAndView;
    }
}

SensitiveWordException

public class SensitiveWordException extends Exception{
    String word;

    public SensitiveWordException(String word, String message) {
        super(message);
        this.word = word;
    }

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }
}

application.xml
在这里插入图片描述
hello.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>hello world</h1>
</body>
</html>

exception.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>正在维护,,,,,</h1>
</body>
</html>

sensitive.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1> ${word}举起手来，${messagez}已经被包围了</h1>
</body>
</html>

web.jsp

<?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">
    <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:application.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

结果：
在这里插入图片描述
在这里插入图片描述
在这里插入图片描述

5.案例五（exception-handler）

在这里插入图片描述
BaseRespVo

@Data
public class BaseRespVo<T> {
    T data;
    String message;
    int errno;
    public static BaseRespVo fail(String message){
        BaseRespVo baseRespVo = new BaseRespVo();
        baseRespVo.setMessage(message);
        baseRespVo.setErrno(500);
        return baseRespVo;
    }
}

ExceptionController

异常和Handler之间的映射，灵活 → 个性化的处理

根据异常的类型不同直接映射到不同的方法上 → ModelAndView还是json
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@RestControllerAdvice
在这里插入图片描述

@ControllerAdvice //使用该注解，才能够使用ExceptionHandler
//@RestControllerAdvice
public class ExceptionController {

    //方法的写法和HandlerMethod写法一毛一样
    @ExceptionHandler(ArithmeticException.class)
    public String exception(ArithmeticException exception){ //ModelAndView
        return "/WEB-INF/exception.jsp";
    }

    @ExceptionHandler(SensitiveWordException.class)
    @ResponseBody
    public BaseRespVo sensitive(SensitiveWordException exception){ //json
        String message = exception.getMessage();
        return BaseRespVo.fail(message);
    }
}
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