SpringMVC基礎知識(3)

阿新 • • 發佈：2021-07-09

1、SpringMVC的返回JSON資料

　　到目前為止我們編寫的所有Controller的方法的返回值都是String型別，但是大家應該都知道，我們有時候資料傳遞特別是在ajax中，我們返回的資料經常需要使用json，那麼如何來保證返回的資料的是json格式呢？使用@ResponseBody註解

　　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.llxazy</groupId>
    <artifactId>springmv_ajax</artifactId>
    <version>1.0-SNAPSHOT</version>
    < 
dependencies>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</ 
version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.0</version>
            <scope>provided</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.10.3</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.10.3</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.10.3</version>
        </dependency>
    </dependencies>
</project>

　　springmvc.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">

    <context:component-scan base-package="com.llxazy"></context:component-scan>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/page/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>
    <mvc:default-servlet-handler></mvc:default-servlet-handler>
    <mvc:annotation-driven></mvc:annotation-driven>
</beans>

　　JsonController.java

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

@Controller
public class JsonController {

    @ResponseBody
    @RequestMapping("/json")
    public List<User> json(){
        List<User> list = new ArrayList<User>();
        list.add(new User(1,"zhangsan",12,"男",new Date(),"[email protected]"));
        list.add(new User(2,"zhangsan2",12,"男",new Date(),"[email protected]"));
        list.add(new User(3,"zhangsan3",12,"男",new Date(),"[email protected]"));
        return list;
    }
}

　　User.java

package com.llxazy.bean;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnore;

import java.util.Date;

public class User {

    private Integer id;
    private String name;
    private Integer age;
    private String gender;
    @JsonFormat( pattern = "yyyy-MM-dd")
    private Date birth;
    @JsonIgnore
    private String email;

    //set、get、toString和構造方法省略
}

　　同時@ResponseBody可以直接將返回的字串資料作為響應內容

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.http.HttpEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class OtherController {
    @ResponseBody
    @RequestMapping("/testResponseBody")
    public String testResponseBody(){
        return "<h1>success</h1>";
    }
}

2、傳送ajax請求獲取json資料

　　ajax.jsp

<%@ page import="java.util.Date" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <script type="text/javascript" src="script/jquery-1.9.1.min.js"></script>
</head>
<%
    pageContext.setAttribute("ctp",request.getContextPath());
%>
<body>
<%=new Date()%>
<a href="${ctp}/json">獲取使用者資訊</a>
<div>

</div>
<script type="text/javascript">
    $("a:first").click(function () {
        $.ajax({
            url:"${ctp}/json",
            type:"GET",
            success:function (data) {
                console.log(data)
                $.each(data,function() {
                    var user = this.id+"--"+this.name+"--"+this.age+"--"+this.gender+"--"+this.birth+"--"+this.email;
                    $("div").append(user+'<br/>');
                })
            }
        });
        return false;
    });
</script>
</body>
</html>

3、使用@RequestBody獲取請求體資訊

　　同時@RequestBody能夠接受json格式的請求資料：

　　testOther.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<script type="text/javascript" src="script/jquery-1.9.1.min.js"></script>
<html>
<%
    pageContext.setAttribute("ctp",request.getContextPath());
%>
<head>
    <title>Title</title>
</head>
<body>
<form action="${ctp}/testRequestBody" method="post" enctype="multipart/form-data">
    <input name="username" value="zhangsan"><br>
    <input name="password" value="123456"><br>
    <input type="file" name="file" ><br>
    <input type="submit"><br>
</form>
<hr/>
<a href="${ctp}/testRequestJson">傳送json資料</a>
<script type="text/javascript">
    $("a:first").click(function () {
        var user = {id:"1",name:"zhangsan",age:"12",gender:"男",birth:"2020-3-13",email:"[email protected]"};
        var userJson = JSON.stringify(user);
       $.ajax({
           url:"${ctp}/testRequestJson",
           type:"POST",
           data:userJson,
           contentType:"application/json",
           success:function (data) {
               alert(data);
           }
       });
       return false;
    });
</script>
</body>
</html>

　　OtherController.java

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class OtherController {

    @RequestMapping("/testRequestBody")
    public String testRequestBody(@RequestBody String body){
        System.out.println("請求體："+body);
        return "success";
    }

    @RequestMapping("/testRequestJson")
    public String testRequestBody(@RequestBody User user){
        System.out.println("物件："+user);
        return "success";
    }
}

　　在接受請求的時候還可以使用HttpEntity物件，用來接受引數，可以獲取請求頭資訊。

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.http.HttpEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class OtherController {

    @RequestMapping("/testHttpEntity")
    public String testRequestBody(HttpEntity<String> httpEntity){
        System.out.println(httpEntity);
        return "success";
    }
}

4、使用RespsonseEntity可以用來定製響應內容

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class OtherController {

    @RequestMapping("/testResponseEntity")
    public ResponseEntity<String> testResponseEntity(){

        String body = "<h1>hello</h1>";
        MultiValueMap<String,String> header = new HttpHeaders();
        header.add("Set-Cookie","name=zhangsan");
        returnnew ResponseEntity<String>(body,header, HttpStatus.OK);
    }
}

5、檔案下載

package com.llxazy.controller;

import com.llxazy.bean.User;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

@Controller
public class OtherController {

    @RequestMapping("/download")
    public ResponseEntity<byte[]> download(HttpServletRequest request) throws Exception {
        //獲取要下載檔案的路徑及輸入流物件
        ServletContext servletContext = request.getServletContext();
        String realPath = servletContext.getRealPath("/script/jquery-1.9.1.min.js");
        FileInputStream fileInputStream = new FileInputStream(realPath);

        byte[] bytes = new byte[fileInputStream.available()];
        fileInputStream.read(bytes);
        fileInputStream.close();
        //將要下載檔案內容返回
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.set("Content-Disposition","attachment;filename=jquery-1.9.1.min.js");
        return  new ResponseEntity<byte[]>(bytes,httpHeaders,HttpStatus.OK);
    }
}

6、檔案上傳

　　Spring MVC 為檔案上傳提供了直接的支援，這種支援是通過即插即用的 MultipartResolver 實現的。Spring 用 Jakarta Commons FileUpload 技術實現了一個 MultipartResolver 實現類：CommonsMultipartResovler

　　Spring MVC 上下文中預設沒有裝配 MultipartResovler，因此預設情況下不能處理檔案的上傳工作，如果想使用 Spring 的檔案上傳功能，需現在上下文中配置 MultipartResolver。

　　pom.xml

    　　<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.4</version>
        </dependency>

　　springmvc.xml

　　 <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="defaultEncoding" value="UTF-8"></property>
        <property name="maxUploadSize" value="1024000"></property>
    </bean>

　　index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <form action="testUpload" method="post" enctype="multipart/form-data">
    檔案: <input type="file" name="file"/><br><br>
    描述: <input type="text" name="desc"/><br><br>
    <input type="submit" value="提交"/>
  </form>
  </body>
</html>

　　UploadHandler.java

package com.llxazy.controller;

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.multipart.MultipartFile;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

@Controller
public class UploadHandler {

    @RequestMapping(value = "/testUpload", method = RequestMethod.POST)
    public String testUpload(@RequestParam(value = "desc", required = false) String desc, @RequestParam("file") MultipartFile multipartFile) throws IOException {
        System.out.println("desc : " + desc);
        System.out.println("OriginalFilename : " + multipartFile.getOriginalFilename());
        multipartFile.transferTo(new File("D:\\file\\"+multipartFile.getOriginalFilename()));

        return "success"; //增加成功頁面: /views/success.jsp
    }
}

　　如果是多檔案上傳

<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <form action="testUpload" method="post" enctype="multipart/form-data">
    檔案: <input type="file" name="file"/><br><br>
    檔案: <input type="file" name="file"/><br><br>
    檔案: <input type="file" name="file"/><br><br>
    描述: <input type="text" name="desc"/><br><br>
    <input type="submit" value="提交"/>
  </form>
  </body>
</html>

　　UploadHandler.java

package com.llxazy.controller;

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.multipart.MultipartFile;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

@Controller
public class UploadHandler {

    @RequestMapping(value = "/testUpload", method = RequestMethod.POST)
    public String testUpload(@RequestParam(value = "desc", required = false) String desc, @RequestParam("file") MultipartFile[] multipartFile) throws IOException {
        System.out.println("desc : " + desc);
        for (MultipartFile file : multipartFile) {
            if (!file.isEmpty()) {
                System.out.println("OriginalFilename : " + file.getOriginalFilename());
                file.transferTo(new File("D:\\file\\" + file.getOriginalFilename()));
            }
        }

        return "success"; //增加成功頁面: /views/success.jsp
    }
}

7、Springmvc攔截器

　　SpringMVC提供了攔截器機制，允許執行目標方法之前進行一些攔截工作或者目標方法執行之後進行一下其他相關的處理。自定義的攔截器必須實現HandlerInterceptor介面。

　　preHandle()：這個方法在業務處理器處理請求之前被呼叫，在該方法中對使用者請求 request 進行處理。如果程式設計師決定該攔截器對請求進行攔截處理後還要呼叫其他的攔截器，或者是業務處理器去進行處理，則返回true；如果程式設計師決定不需要再呼叫其他的元件去處理請求，則返回false

　　postHandle()：這個方法在業務處理器處理完請求後，但是DispatcherServlet 向客戶端返回響應前被呼叫，在該方法中對使用者請求request進行處理。

　　afterCompletion()：這個方法在DispatcherServlet完全處理完請求後被呼叫，可以在該方法中進行一些資源清理的操作。

SpringMVC基礎知識(3)

1、SpringMVC的返回JSON資料

2、傳送ajax請求獲取json資料

3、使用@RequestBody獲取請求體資訊

4、使用RespsonseEntity可以用來定製響應內容

5、檔案下載

6、檔案上傳

7、Springmvc攔截器

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SpringMVC基礎知識(3)

1、SpringMVC的返回JSON資料

2、傳送ajax請求獲取json資料

3、使用@RequestBody獲取請求體資訊

4、使用RespsonseEntity可以用來定製響應內容

5、檔案下載

6、檔案上傳

7、Springmvc攔截器

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