SpringMvc learning - create a new springWeb project in idea & browser request and server response & SpringMvc file related

lead out

---

What is mvc, what is springMvc, how to build a springWeb project,
how to send requests and responses under springMvc, and how to respond?
SpringMvc processing files related: upload files, rename uuid, static resource mapping, yaml configuration path, preliminary spring configuration file;

Basic knowledge: three-tier architecture and MVC

1. Three-tier architecture

1. Presentation (view) layer: WEB layer, used for data interaction with clients. servlet-controller
2. Business layer: service that handles company-specific business logic
3. Persistence layer: dao-mapper used to operate the database

2. MVC model

1. The full name of MVC is Model View Controller Model View Controller, and each part performs its own duties.

2. Model: data model, JavaBean class, used for data encapsulation.

3. View: Refers to JSP and HTML used to display data to users Android-http, Apple, applets

4. Controller: used to receive user requests, the controller of the entire process. Used for data verification, etc.

springWeb project IDEA construction

1. Create a new normal maven project

2. Import package, pom.xml file

(1) Inherit a parent

    <!--    继承一个父-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
    </parent>

(2) Package of web project + front-end template engine

       <!--    做web项目的包-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
<!--        前端模板引擎，类似于jsp-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

(3) Complete pom.xml file

<?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.tianju</groupId>
    <artifactId>springMvc620</artifactId>
    <version>1.0-SNAPSHOT</version>

<!--    继承一个父-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
    </parent>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>

        <!--    做web项目的包-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

<!--        前端模板引擎，类似于jsp-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        
<!--        其他需要的包-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>2.0.22</version>
        </dependency>

    </dependencies>
    
</project>

3. Write the main startup class Main.java file @SpringBootApplication

Main points:

• It is the configuration class of spingMvc: @SpringBootApplication;
• Start: SpringApplication.run(Main.class);
• The problem of directory hierarchy, and other directories of the same level;

Main.java file

package com.tianju;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;


/**
 * springMvc的主启动类
 * 1.本质是配置类；@SpringBootApplication :@Configuration是它的爷爷辈
 * 2.启动容器，SpringApplication.run(Main.class);
 */
@SpringBootApplication
public class Main {
    
    
    public static void main(String[] args) {
    
    
        // 集成了的new对象，放容器，启动执行
        ApplicationContext ac = SpringApplication.run(Main.class);
    }
}

4. Write the application.yml file spring configuration file

Main points:

• The file name is application.yml
• If the color is yellow, there must be a space

server:
  port: 80

5. Start, run main.java to start

SpringMvc browser request preliminary

1. Getting to know springMvc @RequestMapping("/demo")

Main points:

• 1. The controller should be in the container: @Controller
• 2. Used to process browser requests: @RequestMapping(“/demo”)
• @RequestMapping("/demo") can be on the class or on the method: first-level and second-level directories;

ResponseControllerDemo.java file

package com.tianju.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    
    @RequestMapping({
    
    "/hello","/hello2"}) // 二级目录
    @ResponseBody
    public String hello(){
    
    
        return "Hello SpringMvc";
    }
}

2. Derived from @RequestMapping

@PostMapping，@GetMapping，@DeleteMapping，@PutMapping

@RequestMapping

@PostMapping(“/hello”)
@GetMapping
@DeleteMapping
@PutMapping

405 exception: the server can only process post, and the browser requests the get method

The way the browser requests Request to pass parameters

1. Basic data types and String

Main points:

• If the string is not passed, the default is an empty string;
• Integer is not passed, the default is null;

http://localhost/demo/hello?username=&age=

package com.tianju.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    
    @RequestMapping("/hello") // 二级目录
    @ResponseBody
    public String hello(String username,Integer age){
    
    
        System.out.println(username);
        System.out.println(age);
        return "Hello SpringMvc";
    }
}

2. Send name, receive is username, @RequestParam(value = "name")

Main points:

• By default, the value must be passed, and if it is not passed, a 400 exception will be reported;

• If you don't want to pass it, add required=false;

• You can also give a default value, defaultValue="admin"; [Application: When paging, the default is the first page, and the default is 10 data per page]

http://localhost/demo/hello?name=hell

    @RequestMapping("/hello") // 二级目录
    @ResponseBody
    public String hello(@RequestParam(value = "name") String username){
    
    
        System.out.println(username);
        return "Hello SpringMvc";
    }

400 exception, added @RequestParam(value = "name") must pass value

400 exception, the backend type is Integer, the frontend is string, and the conversion fails

2. [Application] You can use @RequestParam(value = “pageNum”, defaultValue = “1”) for pagination

package com.tianju.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    
    @RequestMapping("/hello") // 二级目录
    @ResponseBody
    public String hello(@RequestParam(value = "pageNum",defaultValue = "1") Integer pageNum,
                        @RequestParam(value = "pageSize",defaultValue = "10") Integer pageSize){
    
    
        System.out.println(pageNum);
        System.out.println(pageSize);
        return "Hello SpringMvc";
    }
}

3.Rest style query xxx/search/mobile phone/white----xxx/search?item=mobile phone&color=white

Main points:

• Access path: @RequestMapping("/search/{item}/{color}");
• Get parameters: @PathVariable("item")

http://localhost/demo/search/mobilephone/red

package com.tianju.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.security.SignedObject;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    

    // http://localhost/demo/search/mobilephone/red
    @RequestMapping("/search/{item}/{color}") // 二级目录
    @ResponseBody
    public String hello(@PathVariable("item") String item,
                        @PathVariable("color") String color){
    
    
        System.out.println(item);
        System.out.println(color);
        return "Hello SpringMvc";
    }
}

4. The backend uses object reception + array/collection

Main points:

• Objects can be used to receive data from the front end, and the mapping will be done automatically
• Arrays or collections can be passed

http://localhost/demo/add/user?username=peter&password=123&hobby=learn&hobby=game

package com.tianju.controller;

import com.tianju.entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.security.SignedObject;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    

    // http://localhost/demo/add/user?username=peter
    // &password=123&hobby=learn&hobby=game
    @RequestMapping("/add/user") // 二级目录
    @ResponseBody
    public String hello(User user){
    
    
        System.out.println(user);
        return "Hello SpringMvc";
    }
}

5. Date processing, the default format is 2021/05/28, [to be continued]

Main points:

• By default, only dates in the format of 2021/05/28 can be sent

http://localhost/demo/date?birthday=2021/05/28

package com.tianju.controller;

import com.tianju.entity.User;
import lombok.Data;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.security.SignedObject;
import java.util.Date;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    

    // http://localhost/demo/date?birthday=2021/05/28
    @RequestMapping("/date") // 二级目录
    @ResponseBody
    public String hello(Date birthday){
    
    
        System.out.println(birthday);
        return "Hello SpringMvc";
    }
}

400 exception, date format conversion failed

Failed to convert from type [java.lang.String] to type [java.util.Date] for value ‘2021-5-28’; nested exception is java.lang.IllegalArgumentException]

6. How to get the request header, the value in the cookie, and the original request and response, etc.

Main points:

• write what you need;

• HttpServletRequest request,

• HttpSession httpSession,

http://localhost/demo/set/session
http://localhost/demo/native

package com.tianju.controller;

import com.tianju.entity.User;
import lombok.Data;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.security.SignedObject;
import java.util.Date;

/**
 * controller层，
 * 1.在容器中: @Controller
 * 2.用来处理网络请求：即 @RequestMapping("/demo")
 * 既可以放在类上：一级目录；
 * 也可以在方法上：二级目录：http://localhost/demo/hello
 */
@Controller
@RequestMapping("/demo") // 一级目录
public class ResponseControllerDemo {
    
    

    // http://localhost/demo/date?birthday=2021/05/28
    @RequestMapping("/native") // 二级目录
    @ResponseBody
    public String hello(HttpServletRequest request,
                        HttpSession httpSession,
                        HttpServletResponse response,
                        @RequestHeader("Connection") String connection,
                        @CookieValue("JSESSIONID") String jsessionid){
    
    
        // 1.request里面就可以获得session，之前servlet就是这样的
        HttpSession session = request.getSession();
        // 2.加上httpSession，也能获得；
        Object username = httpSession.getAttribute("username");
        System.out.println(username);
        System.out.println(response);
        System.out.println("----获取请求头里的connection------");
        System.out.println(connection);
        System.out.println(jsessionid);
        return "Hello SpringMvc";
    }

    @RequestMapping("/set/session")
    @ResponseBody
    public String setSession(HttpSession session){
    
    
        session.setAttribute("username", "peter");
        System.out.println(session);
        return "success";
    }
}

Request header
to get connection and jsessionid

The server responds with Response—the backend sends content to the frontend

Need a package, front-end template engine, similar to jsp

<!--        前端模板引擎，功能类似于jsp-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

1. Respond to a Json + time display @JsonFormat [with pits]

Main points:

• The response is json, add @ResponseBody;

• For the time display problem, GMT+8 is required:

• @JsonFormat(pattern = “yyyy-MM-DD hh:mm:ss”, timezone = “GMT+8”)

• If a controller response is all json, @RestController can be used instead of @Controller and @ResponseBody

Note here, the date conversion format is wrong, DD should be changed to lowercase dd

date format conversion

    @JsonFormat(pattern = "yyyy-MM-dd hh:mm:ss",timezone = "GMT+8")
    private Date birthday;

controller's code

package com.tianju.controller;

import com.tianju.entity.ResData;
import com.tianju.entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.Arrays;
import java.util.Date;

/**
 * 响应相关：1.响应json；2.响应页面
 * 要点：
 * 1.在容器@Controller；
 * 2.路径；@RequestMapping("/resp")；
 * 3.如果是响应json，需要加@ResponseBody;
 * 4.如果响应页面，则返回值是string
 * 补充：如果一个controller响应都是json
 * 则，@RestController代替 @Controller 和 @ResponseBody
 */
@Controller
@RequestMapping("/resp")
//@RestController // 等价于@Controller + @ResponseBody
public class ResponseControllerDemo {
    
    
    @RequestMapping("/json")
    @ResponseBody // 如果响应是json，必须加
    public ResData respJson(){
    
    
        User user = new User("peter", "123",
                new Date(), Arrays.asList(new String[]{
    
    "learn","movie"}));
        return new ResData(200, "success", user);
    }
}

You can not write responseBody, use @RestController

2. Respond to a page and return the value String

Main points:

• 1. The return value is string;
• 2. Responsebody cannot be added

The server responds to the html code and displays it on the front-end page

Access to files under resources can be modified, not recommended

access connection

http://localhost/resp/list

backend code

    /**
     * 响应一个页面
     * @return list页面，会在前面拼 /templates，后面拼.html
     * 最终访问到xxx/templates/opus/list.html
     */
    @RequestMapping("/list")
    public String respHtml(){
    
    
        return "/opus/list";
    }

2. Response page, ModelAndView and shared data [[${usename}]]

Main points:

<html lang="en" xmlns:th="http://www.thymeleaf.org">

// 1.定义要跳转的页面，2.添加要共享的数据
        ModelAndView mv = new ModelAndView("opus/list");
        mv.addObject("username", "peter");

The first way: not recommended

The second method: this method will be used to share data in the future

Shared values ​​are displayed to the frontend

    @RequestMapping("/listAndData")
    public ModelAndView respHtmlData(){
    
    
        // 1.定义要跳转的页面，2.添加要共享的数据
        ModelAndView mv = new ModelAndView("opus/list");
        mv.addObject("username", "peter");
        return mv;
    }

3. If you want to handle it yourself, use void

Key points: no return value, use void

package com.tianju.controller;

import com.alibaba.fastjson.JSON;
import com.tianju.entity.ResData;
import com.tianju.entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
import java.util.Date;

/**
 * 响应相关：1.响应json；2.响应页面
 * 要点：
 * 1.在容器@Controller；
 * 2.路径；@RequestMapping("/resp")；
 * 3.如果是响应json，需要加@ResponseBody;
 * 4.如果响应页面，则返回值是string
 * 补充：如果一个controller响应都是json
 * 则，@RestController代替 @Controller 和 @ResponseBody
 */
@Controller
@RequestMapping("/resp")
//@RestController // 等价于@Controller + @ResponseBody
public class ResponseControllerDemo {
    
    
    @RequestMapping("/json")
    @ResponseBody // 如果响应是json，必须加
    public ResData respJson(){
    
    
        User user = new User("peter", "123",
                new Date(), Arrays.asList(new String[]{
    
    "learn","movie"}));
        return new ResData(200, "success", user);
    }

    /**
     * 响应一个页面
     * @return list页面，会在前面拼 /templates，后面拼.html
     * 最终访问到xxx/templates/opus/list.html
     */
    @RequestMapping("/list")
    public String respHtml(){
    
    
        return "/opus/list";
    }

    @RequestMapping("/listAndData")
    public ModelAndView respHtmlData(){
    
    
        // 1.定义要跳转的页面，2.添加要共享的数据
        ModelAndView mv = new ModelAndView("opus/list");
        mv.addObject("username", "peter");
        return mv;
    }

    /**
     * 如果想自己处理，就用void
     */
    @RequestMapping("/self")
    public void test(HttpServletResponse response) throws IOException {
    
    
        ResData resData = new ResData(200, "success", null);
        response.getWriter().write(JSON.toJSONString(resData));
    }
}

SpringMvc handles uploading files

1. Upload the file and save it to the local MultipartFile

Main points:

• 1. Submit with post + segment submission enctype="multipart/form-data";
• 2. Receive with MultipartFile to receive, you can get the name size, etc.;
• 3. Save to the local can use transferTo, or get the input stream processing;

You can get the picture, get the size of the picture, and process the size

Backend controller code

package com.tianju.controller;

import com.tianju.entity.ResData;
import org.apache.commons.io.IOUtils;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

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

/**
 * 上传文件：
 * 要点：
 * 1.前端怎么提交：
 * 2.后端怎么接收：
 * 3.接收后怎么处理：
 */
//@RestController // 等价于@Controller 和 @ResponseBody
@Controller
@RequestMapping("/file")
public class UploadController {
    
    
    // 1.先到上传图片的页面
    @RequestMapping("/uploadPage")
    public String uploadPage(){
    
    
        return "/opus/upload";
    }

    // 2.处理前端上传的图片
    @RequestMapping("/upload")
    @ResponseBody
    public ResData uploadImg(MultipartFile headImg) throws IOException {
    
    
        long size = headImg.getSize(); // 文件大小
        String filename = headImg.getOriginalFilename(); // 文件名
        System.out.println("上传的文件："+filename+"，文件大小"+size);
        // 对文件进行处理
        // (1)拿到输入流，然后保存到本地；以后也可能通过网络发送到其他地方
        InputStream inputStream = headImg.getInputStream();
        FileOutputStream outputStream = new FileOutputStream("D:/06/" + filename);
        IOUtils.copy(inputStream, outputStream);
        // 谁建的谁关
        outputStream.close();

        // (2)不用流直接存到本地文件中
        headImg.transferTo(new File("D:\\620\\"+filename));
        return new ResData(200, "ok", null);
    }

}

Front-end upload.html page code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<!-- 提交方法必须是post，并且用分段提交 -->
<form action="/file/upload"
      method="post"
      enctype="multipart/form-data">
    <input type="file" name="headImg">
    <input type="submit" value="提交">
</form>

</body>
</html>

2. The problem of uploading files with the same name being overwritten—rename with uuid

Main points:

• 1. Rename with uuid, remove - from uuid, replace method;
• 2. Get the suffix of the uploaded file int i = originalFilename.lastIndexOf(“.”); substring(i);
• 3. Save to local

package com.tianju.controller;

import com.tianju.entity.ResData;
import org.apache.commons.io.IOUtils;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.UUID;

/**
 * 上传文件：
 * 要点：
 * 1.前端怎么提交：
 * 2.后端怎么接收：
 * 3.接收后怎么处理：
 */
//@RestController // 等价于@Controller 和 @ResponseBody
@Controller
@RequestMapping("/file")
public class UploadController {
    
    
    // 1.先到上传图片的页面
    @RequestMapping("/uploadPage")
    public String uploadPage(){
    
    
        return "/opus/upload";
    }

    // 2.处理前端上传的图片
    @RequestMapping("/upload")
    @ResponseBody
    public ResData uploadImg(MultipartFile headImg) throws IOException {
    
    
        long size = headImg.getSize(); // 文件大小
        String originalFilename = headImg.getOriginalFilename(); // 文件名
        System.out.println("上传的文件："+originalFilename+"，文件大小"+size);
        // 对文件进行处理 (2)不用流直接存到本地文件中
        // 获得uuid，并把中间-去掉
        String randomStr = UUID.randomUUID().toString().replace("-", "");
        // 获取上传文件的后缀
        int i = originalFilename.lastIndexOf(".");
        String suffix = originalFilename.substring(i, originalFilename.length());
        headImg.transferTo(new File("D:\\620\\"+randomStr+suffix));
        return new ResData(200, "ok", null);
    }

}

3. Local computer pictures for display—static resource mapping—protocol file:

Main points:

• 1. Create a new configuration class to implement the WebMvcConfigurer interface;
• 2. addResourceHandlers method, local file protocol file:

Local file protocol, /** indicates that subdirectories can also be found

Web page access to local images

springMvcConfig.java file

package com.tianju.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * springMvc的配置类，spring的相关配置都在这里
 * 要点：
 * 1.是配置类；@Configuration
 * 2.是springMvc的配置类：implements WebMvcConfigurer
 */
@Configuration
public class SpringMvcConfig implements WebMvcConfigurer {
    
    

    /**
     * 能够把服务器上的一个目录，映射成一个路径，http可以直接访问到
     * @param registry
     */
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
    
    
        // 在浏览器上，如果访问/bookImg/1.jpg，springMvc就去D:\620\1.jpg找对应的文件
        // /bookimg/** 表示子目录下的文件也能找到
        registry.addResourceHandler("/bookimg/**")
                .addResourceLocations("file:D:\\620\\");
    }
}

4. Put the path of the uploaded file in the spring configuration file and get @Value(“${imgLocation}”)

Main points:

• Configure in the application.yml file;
• Get it through @Value("${imgLocation}";

application.yml file

server:
  port: 80

## 图片上传的路径
imgLocation: D:\\620\\

Other file acquisition:

package com.tianju.config;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * springMvc的配置类，spring的相关配置都在这里
 * 要点：
 * 1.是配置类；@Configuration
 * 2.是springMvc的配置类：implements WebMvcConfigurer
 */
@Configuration
public class SpringMvcConfig implements WebMvcConfigurer {
    
    
    @Value("${imgLocation}")
    private String imgLocation;

    /**
     * 能够把服务器上的一个目录，映射成一个路径，http可以直接访问到
     * @param registry
     */
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
    
    
        // 在浏览器上，如果访问/bookImg/1.jpg，springMvc就去D:\620\1.jpg找对应的文件
        // /bookimg/** 表示子目录下的文件也能找到
        registry.addResourceHandler("/bookimg/**")
                .addResourceLocations("file:"+imgLocation);
    }
}

---

Summarize

1.Model View Controller model view controller;
2.idea builds a springWeb project, a common project, inheriting a parent, the main startup class @SpringBootApplication, application.yml configuration file;
3. Browser request @RequestMapping("/demo"), It can be used on classes, methods, first-level and second-level directories;
4. Request parameter @RequestParam(value = "pageNum", defaultValue = "1"), which can be used on pagination;
5. Request: query xxx/search/mobile /white, @RequestMapping("/search/{item}/{color}")----@PathVariable("item");
6. Request: get request, parameter plus HttpServletRequest request;
7. Server response, response Page, respond to json, handle it yourself;
8. Respond to JSON, @ResponseBody, time format, @JsonFormat(pattern = "yyyy-MM-DD hh:mm:ss", timezone = "GMT+8"); 9. Response
page : The return value is string, and @ResponseBody cannot be added;
10. Response page with some data: ModelAndView and shared data [[${usename}]];
11. Upload file MultipartFile reception, segmented post submission: enctype="multipart/form -data";
12. Static resource mapping: springMvcConfig configuration class @Configuration, implement interface WebMvcConfigurer, addResourceHandlers method, local file protocol file:/;
13. Get the value in the application.yml file, use @Value(" $ {imgLocation}";