[Java知识库] SpringMVC（一）

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[Java知识库]SpringMVC（一）

一、引用接口开发

1.首先在web.xml中配置DispatcherServlet

<?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DispatcherServlet：请求分发器，前端控制器  -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!--    DispatcherServlet绑定Spring配置问文件    -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc-servlet.xml</param-value>
        </init-param>
        <!--    启动级别：1    -->
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

2.配置springmvc-servlet.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<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 ">
    <!--处理器映射器-->
    <bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/>
    <!--处理器适配器-->
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>
    <!--  视图解析器  -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
        <!--    前缀    -->
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <!--    后缀    -->
        <property name="suffix" value=".jsp"/>

    </bean>

    <bean id="/hello" class="com.kuang.controller.HelloController"/>

</beans>

3.在servlet层填写业务逻辑

package com.kuang.controller;

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

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

public class HelloController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {

        ModelAndView mv = new ModelAndView();
        //业务代码 attributeName：业务名字、attrValue：业务值
        mv.addObject("msg","HelloSpringMVC");
        //视图跳转
        mv.setViewName("hello");
        
        return mv;
    }
}

4.创建视图内容

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${msg}
</body>
</html>

二、注解开发

1.配置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>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

2.配置springmvc-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: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
           https://www.springframework.org/schema/context/spring-context.xsd
           http://www.springframework.org/schema/mvc
           https://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <!--  自动扫描包，让指定包下的注解生效，由IOC容器统一管理  -->
    <context:component-scan base-package="com.kuang.controller"/>
    <!--  让SpringMVC不处理静态资源  -->
    <mvc:default-servlet-handler/>
    <!--
      支持mvc注解驱动：
        在spring中一般采用@RequestMapping注解来完成映射关系
        想要使@RequestMapping注解生效
        必须向上下文注册DefaultAnnotationHandlerMapping
        和一个A你弄他汀MethodHandlerAdapter实例
        这两个实例分别在类级别和方法级别处理
        而annotation-driven配置帮助我们自动完成上述两个实例的注入
      -->
    <mvc:annotation-driven/>
    <!--  视图解析器  -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
        <!--    前缀    -->
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <!--    后缀    -->
        <property name="suffix" value=".jsp"/>
    </bean>
</beans>

3.配置Controller层

package com.kuang.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller//代表这个类被Spring托管
           //被这个注解的类，中的所有方法，如果返回值是String，并且有具体页面可以跳转，那么就会被视图解析器解析
public class ControllerTest2 {

//    @PathVariable可以直接在url中传输变量
    @RequestMapping(value = "/t2/{a}/{b}",method = RequestMethod.GET)
    public String test1(@PathVariable int a,@PathVariable int b, Model model){
        int res = a+b;
        model.addAttribute("msg","ControllerTest2"+res);
        return "test";
    }
    @RequestMapping(value = "/t2/{a}/{b}",method = RequestMethod.POST)
    public String test2(@PathVariable int a,@PathVariable int b, Model model){
        int res = a+b;
        model.addAttribute("msg","ControllerTest3"+res);
        return "test";
    }
}

4.配置前端页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${msg}
</body>
</html>

三、将数据传回前端

1.Model：只有几个方法，适用于存储数据

//@RequestParam重命名参数，前端发送username就可以连接到name，username和name不能同时使用
    @GetMapping("/t1")
    public String test1(@RequestParam("username") String name, Model model){
//        1.接收前端参数
        System.out.println("接收到前端的参数为："+name);
//        2.将返回的结果传输给前端
        model.addAttribute("msg",name);
//        3.视图跳转
        return "test";
    }

2.Modelmap：继承了LinkedMap，除了实现自身的一些方法，集成LinkedMap的方法和特性

3.LinkedMap：可以在存储数据的同时进行设置返回的逻辑视图，进行控制转换层的跳转

4ModelAndView：

    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
        ModelAndView mv = new ModelAndView();
        mv.addObject("msg","ControllerTest1");
        mv.setViewName("test");
        return mv;
    }

四、JSON的使用

JSON作为前后端交互的纽带，负责将后端的JavaScript对象转换为iString类型传回前端，也可以将JSON字符串转换为JavaScript对象，传回后端。

1.JSON使用流程

1.1导入JSON包

1.2将乱码配置在spring-servlet.xml中(如2.2)

1.3新建ObjectMapper对象，传入实体类，将其转换成Spring

@Controller
public class UserController {
    @RequestMapping(value = "/j1")
    @ResponseBody//添加该注解就不会走视图解析器，会直接返回一个字符串
    public String json1() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
//        创建一个对象
        User user = new User(123,"高崧豪", 23);
        String str = mapper.writeValueAsString(user);
        return str;
    }
}

此处可以将@ResponseBody删除，将@Controller更换为@RestController有同样的效果

2.JSON字符串乱码问题

2.1在RequestMapping中配置字符解析格式(在Controller层操作)

@Controller
public class UserController {
    @RequestMapping(value = "/j1",produces = "application/json;charset=utf-8")
    @ResponseBody//添加该注解就不会走视图解析器，会直接返回一个字符串
    public String json1() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
//        创建一个对象
        User user = new User(123,"高崧豪", 23);
        String str = mapper.writeValueAsString(user);
        return str;
    }
}

2.2在springmvc-servlet.xml中解决JSON乱码问题

    <!--  JSON乱码问题配置  -->
    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

五、其他知识点

1.重定向在controller层，与转发的区别是return部分,页面链接部分也有区别

    @RequestMapping(value = "/t2/{a}/{b}",method = RequestMethod.POST)
    public String test2(@PathVariable int a,@PathVariable int b, Model model){
        int res = a+b;
        model.addAttribute("msg","ControllerTest3"+res);
        return "redirect:/a.jsp";
    }

2.转发在controller层，与重定向的区别是return部分,页面链接部分也有区别

    @RequestMapping(value = "/t2/{a}/{b}",method = RequestMethod.GET)
    public String test1(@PathVariable int a,@PathVariable int b, Model model){
        int res = a+b;
        model.addAttribute("msg","ControllerTest2"+res);
        return "test";
    }

    @RequestMapping(value = "/t2/{a}/{b}",method = RequestMethod.GET)
    public String test1(@PathVariable int a,@PathVariable int b, Model model){
        int res = a+b;
        model.addAttribute("msg","ControllerTest2"+res);
        return "forward:/a.jsp";
    }

3.过滤器，解决页面传入参数时的乱码问题

3.1编写过滤器java代码

package com.kuang.filter;
import javax.servlet.*;
import java.io.IOException;

public class EncodingFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        filterChain.doFilter(servletRequest,servletResponse);
    }
    @Override
    public void destroy() {
    }
}

3.2在web.xml中配置过滤器文件

    <filter>
        <filter-name>encoding</filter-name>
        <filter-class>com.kuang.filter.EncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

3.3url-patten中需设定为/*这样可以覆盖.jsp文件