"SpringMvc Usage" - just for use, one article is enough

Work flow: First, the browser initiates a request to our controller. Then, the controller calls our service business layer, and the service layer calls our dao layer. The dao layer returns data to our service layer, and the service layer returns the data to form a Model. But Model is a Java model that the browser cannot recognize, so at this time View+Model work together at the same time to form a page returned to our browser.

Problem solved: This solves the disadvantages of the above-mentioned three-tier architecture, and one servlet can be used to handle multiple requests. ,

1.1.3, asynchronous call

Workflow: Call our back-end server through asynchronous calling, the back-end server will generate a Model object, and the back-end server will convert the Model object into josn format and return it to our front-end page.

springMvc is responsible for the development of functions corresponding to the controller and converts our data into json format

1.2, Springmvc overview

Natively integrated with Spring
Support Restful style development
Easy to integrate with other view technologies, such as theamleaf, freemarker, etc.
Powerful exception handling
Support for static resources

We will understand these things later.

2. Getting Started Case

2.1, the process of developing web programs with servlet and springmvc

2.2, springmvc develops web programs

2.2.1 First create a web project and import the tomcat7 plug-in in the pom file (I will not demonstrate how to create a web project here, because different idea versions have different creation methods)

<?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.itheima</groupId>
  <artifactId>springmvc_01_quickstart</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.2.10.RELEASE</version>
    </dependency>
  </dependencies>
  
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.tomcat.maven</groupId>
        <artifactId>tomcat7-maven-plugin</artifactId>
        <version>2.1</version>
        <configuration>
          <port>80</port>
          <path>/</path>
        </configuration>
      </plugin>
    </plugins>
  </build>


</project>

2.2.2 Write the configuration class, processor class and web configuration class

Configuration class:

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

//springmvc配置类，本质上还是一个spring配置类
@Configuration
@ComponentScan("com.itheima.controller")
public class SpringMvcConfig {
}

Processing class:

package com.itheima.controller;

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

//定义表现层控制器bean
@Controller
public class UserController {

    //设置映射路径为/save，即外部访问路径
    @RequestMapping("/save")
    //设置当前操作返回结果为指定json数据（本质上是一个字符串信息）
    @ResponseBody
    public String save(){
        System.out.println("user save ...");
        return "{'info':'springmvc'}";
    }

    //设置映射路径为/delete，即外部访问路径
    @RequestMapping("/delete")
    @ResponseBody
    public String delete(){
        System.out.println("user save ...");
        return "{'info':'springmvc'}";
    }
}

springmvc configuration class:

package com.itheima.config;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;

//web容器配置类
public class ServletContainersInitConfig extends AbstractDispatcherServletInitializer {
    //加载springmvc配置类，产生springmvc容器（本质还是spring容器）
    protected WebApplicationContext createServletApplicationContext() {
        //初始化WebApplicationContext对象
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        //加载指定配置类
        ctx.register(SpringMvcConfig.class);
        return ctx;
    }

    //设置由springmvc控制器处理的请求映射路径
    protected String[] getServletMappings() {
        //代表所有的请求都是归springmvc处理
        return new String[]{"/"};
    }

    //加载spring配置类
    protected WebApplicationContext createRootApplicationContext() {
        return null;
    }
}

2.2.3, create tomcat server

As shown below, 1. We click to add configuration, 2. Then select maven, 3. Edit the name of the maven project, 4. Select the working directory, 5. Enter the command tomcat7:run to run.

Start the maven project just configured here

2.2.3, Interlude

We can see that an error occurred here. We can see that the port is occupied, so we can change the port.

We modified the tomcat running port in the pom file to 8081, and found that it could run successfully after running it again. So problem solved.

2.2.4, access port

As you can see, we successfully connected.

2.2.5, some small details

1. Since @ResponseBody is added to the save() method body, the returned data will be treated as json data and returned directly to the page. If it is not added, we will return {'info':'springmvc'} It cannot be recognized by the browser, and the browser will report 404 because it thinks you are going to return to the page.

2. Pay attention to the classes inherited by this configuration class, and this configuration class needs to override the following three methods to respond to our requests and responses normally.

//web容器配置类
public class ServletContainersInitConfig extends AbstractDispatcherServletInitializer {
    //加载springmvc配置类，产生springmvc容器（本质还是spring容器）
    protected WebApplicationContext createServletApplicationContext() {
        //初始化WebApplicationContext对象
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        //加载指定配置类
        ctx.register(SpringMvcConfig.class);
        return ctx;
    }

    //设置由springmvc控制器处理的请求映射路径
    protected String[] getServletMappings() {
        //代表所有的请求都是归springmvc处理
        return new String[]{"/"};
    }

    //加载spring配置类
    protected WebApplicationContext createRootApplicationContext() {
        return null;
    }
}

3. Analysis of entry case process

3.1, Start the process of server initialization

web container -> webApplication object -> servletContext (the largest scope in the web container) -> load the bean into the webApplication object.

All mappings are managed together instead of inside the bean.

3.2 Process of a single request

4.Controller loads the controller

In fact, we now have a problem, that is, when we load the bean, springmvc will read the bean, and spring will also read the bean, but how can we prevent spring from reading our controller? There are two methods

4.1 Accurate reading

In our spring configuration class, we configure only to scan two packages, service and dao.

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.stereotype.Controller;

@Configuration
@ComponentScan({"com.itheima.service","com.itheima.dao"})

public class SpringConfig {
}

4.2 Filtering

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.stereotype.Controller;

@Configuration
//设置spring配置类加载bean时的过滤规则，当前要求排除掉表现层对应的bean
//excludeFilters属性：设置扫描加载bean时，排除的过滤规则
//type属性：设置排除规则，当前使用按照bean定义时的注解类型进行排除
//classes属性：设置排除的具体注解类，当前设置排除@Controller定义的bean
@ComponentScan(value="com.itheima",
    excludeFilters = @ComponentScan.Filter(
        type = FilterType.ANNOTATION,
        classes = Controller.class
    )
)
public class SpringConfig {
}

4.3, load springmvc and spring container

package com.itheima.config;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;

public class ServletContainersInitConfig extends AbstractDispatcherServletInitializer {
    //加载springmvc容器
    protected WebApplicationContext createServletApplicationContext() {
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        ctx.register(SpringMvcConfig.class);
        return ctx;
    }
    //加载spring容器
    protected WebApplicationContext createRootApplicationContext() {
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        ctx.register(SpringConfig.class);
        return ctx;
    }
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }

}

The simplified version has the same meaning as above, but the simplified version is what we use most in actual development:

package com.itheima.config;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;
//web配置类简化开发，仅设置配置类类名即可
public class ServletContainersInitConfig extends AbstractAnnotationConfigDispatcherServletInitializer {

    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{SpringConfig.class};
    }

    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{SpringMvcConfig.class};
    }

    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}

2. Request and response

1. Request mapping path

1.1 Define request path prefix

We add @RequestMapping("/user") to the class. At this time, the full path of access is localhost:port number/usr/*

package com.itheima.controller;

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

@Controller
//类上方配置的请求映射与方法上面配置的请求映射连接在一起，形成完整的请求映射路径
@RequestMapping("/user")
public class UserController {
    //请求路径映射
    @RequestMapping("/save")
    @ResponseBody
    public String save(){
        System.out.println("user save ...");
        return "{'module':'user save'}";
    }
    //请求路径映射
    @RequestMapping("/delete")
    @ResponseBody
    public String delete(){
        System.out.println("user delete ...");
        return "{'module':'user delete'}";
    }

}

2. Request parameters

Usercontroller class:

package com.itheima.controller;

import com.itheima.domain.User;
import org.springframework.format.annotation.DateTimeFormat;
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.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.Arrays;
import java.util.Date;
import java.util.List;
//请求参数
@Controller
public class UserController {

    //普通参数：请求参数与形参名称对应即可完成参数传递
    @RequestMapping("/commonParam")
    @ResponseBody
    public String commonParam(String name ,int age){
        System.out.println("普通参数传递 name ==> "+name);
        System.out.println("普通参数传递 age ==> "+age);
        return "{'module':'common param'}";
    }

    //普通参数：请求参数名与形参名不同时，使用@RequestParam注解关联请求参数名称与形参名称之间的关系
    @RequestMapping("/commonParamDifferentName")
    @ResponseBody
    public String commonParamDifferentName(@RequestParam("name") String userName , int age){
        System.out.println("普通参数传递 userName ==> "+userName);
        System.out.println("普通参数传递 age ==> "+age);
        return "{'module':'common param different name'}";
    }

   
}

Ordinary parameters: When the request parameter name is different from the formal parameter name, use the @RequestParam annotation to associate the relationship between the request parameter name and the formal parameter name.

2.1get request and post request

We enter the address http://localhost:8082/commonParam?name=zhansan&age=15 on PostMan , and it is a get request.

You can see that the parameters on the url have been obtained. We will find that the parameters on the url will be automatically passed to our formal parameters.

Then using post request to send, we found that the data can still be returned.

We can know that controller is different from servlet. There are no doGet and doPost methods because it does not distinguish between post and get.

2.3 Specify encoding format

When our URL contains Chinese, we need to use a filter to specify the encoding format, and the method is garbled. We specify this filter in the web configuration class.

The web configuration class code is as follows:

package com.itheima.config;

import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

import javax.servlet.Filter;

public class ServletContainersInitConfig extends AbstractAnnotationConfigDispatcherServletInitializer {
    protected Class<?>[] getRootConfigClasses() {
        return new Class[0];
    }

    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{SpringMvcConfig.class};
    }

    protected String[] getServletMappings() {
        return new String[]{"/"};
    }

    //乱码处理
    @Override
    protected Filter[] getServletFilters() {
        CharacterEncodingFilter filter = new CharacterEncodingFilter();
        filter.setEncoding("UTF-8");
        return new Filter[]{filter};
    }
}

3. Five types of parameter transfer

3.1，pojo

controller：

//POJO参数：请求参数与形参对象中的属性对应即可完成参数传递
    @RequestMapping("/pojoParam")
    @ResponseBody
    public String pojoParam(User user){
        System.out.println("pojo参数传递 user ==> "+user);
        return "{'module':'pojo param'}";
    }

Just pass the parameters here normally, for example url= http://localhost:8082/commonParam?name=zhansan&age=15

3.2, Nested pojo type

Corresponding writing:

@RequestMapping("/pojoContainPojoParam")
    @ResponseBody
    public String pojoContainPojoParam(User user){
        System.out.println("pojo嵌套pojo参数传递 user ==> "+user);
        return "{'module':'pojo contain pojo param'}";
    }

But here there is a little difference when passing parameters. You can see that when we pass parameters to nested types, we need to use object.properties .

3.3, array type

//数组参数：同名请求参数可以直接映射到对应名称的形参数组对象中
    @RequestMapping("/arrayParam")
    @ResponseBody
    public String arrayParam(String[] likes){
        System.out.println("数组参数传递 likes ==> "+ Arrays.toString(likes));
        return "{'module':'array param'}";
    }

When passing parameters, all the parameters you pass will be put into the array. Note that when writing, your key needs to be your array name, not other names.

3.4, set parameters

//集合参数：同名请求参数可以使用@RequestParam注解映射到对应名称的集合对象中作为数据
    @RequestMapping("/listParam")
    @ResponseBody
    public String listParam(@RequestParam List<String> likes){
        System.out.println("集合参数传递 likes ==> "+ likes);
        return "{'module':'list param'}";
    }

The method of passing parameters is the same as the method of array.

4. Respond to json data

4.1, preliminary work

Import json dependencies

    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.0</version>
    </dependency>

Send json data

Add the annotation @EnableWebMvc to the mvc configuration class so that it can convert the received json data into objects.

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

import javax.servlet.Filter;
import javax.servlet.annotation.WebFilter;

@Configuration
@ComponentScan("com.itheima.controller")
//开启json数据类型自动转换
@EnableWebMvc
public class SpringMvcConfig {
}

4.2, json array

controller

//集合参数：json格式
    //1.开启json数据格式的自动转换，在配置类中开启@EnableWebMvc
    //2.使用@RequestBody注解将外部传递的json数组数据映射到形参的集合对象中作为数据
    @RequestMapping("/listParamForJson")
    @ResponseBody
    public String listParamForJson(@RequestBody List<String> likes){
        System.out.println("list common(json)参数传递 list ==> "+likes);
        return "{'module':'list common for json param'}";
    }

Pass parameters:

4.3, json object

controller：

   //POJO参数：json格式
    //1.开启json数据格式的自动转换，在配置类中开启@EnableWebMvc
    //2.使用@RequestBody注解将外部传递的json数据映射到形参的实体类对象中，要求属性名称一一对应
    @RequestMapping("/pojoParamForJson")
    @ResponseBody
    public String pojoParamForJson(@RequestBody User user){
        System.out.println("pojo(json)参数传递 user ==> "+user);
        return "{'module':'pojo for json param'}";
    }

Passing parameters: Pay attention to the format of passing parameters

Assuming that there is a pojo nested inside, the parameters are passed as follows.

4.4, json array (pojo)

controller：

//集合参数：json格式
    //1.开启json数据格式的自动转换，在配置类中开启@EnableWebMvc
    //2.使用@RequestBody注解将外部传递的json数组数据映射到形参的保存实体类对象的集合对象中，要求属性名称一一对应
    @RequestMapping("/listPojoParamForJson")
    @ResponseBody
    public String listPojoParamForJson(@RequestBody List<User> list){
        System.out.println("list pojo(json)参数传递 list ==> "+list);
        return "{'module':'list pojo for json param'}";
    }

Parameter transmission format:

5. Pass date parameters

controller

//日期参数
    //使用@DateTimeFormat注解设置日期类型数据格式，默认格式yyyy/MM/dd
    @RequestMapping("/dataParam")
    @ResponseBody
    public String dataParam(Date date,
                            @DateTimeFormat(pattern="yyyy-MM-dd") Date date1,
                            @DateTimeFormat(pattern="yyyy/MM/dd HH:mm:ss") Date date2){
        System.out.println("参数传递 date ==> "+date);
        System.out.println("参数传递 date1(yyyy-MM-dd) ==> "+date1);
        System.out.println("参数传递 date2(yyyy/MM/dd HH:mm:ss) ==> "+date2);
        return "{'module':'data param'}";
    }

The default standard date format is 2001/3/21. If you use other date formats without processing, an error will be reported. An annotation is also provided here to create the date format you may receive.

An important interface needs to be mentioned here, the convert interface. It has many implementation classes to help us convert data formats.

Supplement: @ResponseBody annotation

The conversion process is implemented for us by a new interface HttpMessageConvert interface, not the convert interface.

This interface can convert our object data into json data and return it.

3. Rest style

1. Introduction to rest style

Principle: Resources are distinguished by access methods (path + request method)

2.restful entry case

package com.itheima.controller;

import com.itheima.domain.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
public class UserController {

    //设置当前请求方法为POST，表示REST风格中的添加操作
    @RequestMapping(value = "/users",method = RequestMethod.POST)
    @ResponseBody
    public String save(){
        System.out.println("user save...");
        return "{'module':'user save'}";
    }

    //设置当前请求方法为DELETE，表示REST风格中的删除操作
    //@PathVariable注解用于设置路径变量（路径参数），要求路径上设置对应的占位符，并且占位符名称与方法形参名称相同
    @RequestMapping(value = "/users/{id}",method = RequestMethod.DELETE)
    @ResponseBody
    public String delete(@PathVariable Integer id){
        System.out.println("user delete..." + id);
        return "{'module':'user delete'}";
    }

    //设置当前请求方法为PUT，表示REST风格中的修改操作
    @RequestMapping(value = "/users",method = RequestMethod.PUT)
    @ResponseBody
    public String update(@RequestBody User user){
        System.out.println("user update..."+user);
        return "{'module':'user update'}";
    }

    //设置当前请求方法为GET，表示REST风格中的查询操作
    //@PathVariable注解用于设置路径变量（路径参数），要求路径上设置对应的占位符，并且占位符名称与方法形参名称相同
    @RequestMapping(value = "/users/{id}" ,method = RequestMethod.GET)
    @ResponseBody
    public String getById(@PathVariable Integer id){
        System.out.println("user getById..."+id);
        return "{'module':'user getById'}";
    }

    //设置当前请求方法为GET，表示REST风格中的查询操作
    @RequestMapping(value = "/users",method = RequestMethod.GET)
    @ResponseBody
    public String getAll(){
        System.out.println("user getAll...");
        return "{'module':'user getAll'}";
    }

}









/*
    @RequestMapping
    @ResponseBody
    public String delete(){
        System.out.println("user delete...");
        return "{'module':'user delete'}";
    }

    @RequestMapping
    @ResponseBody
    public String update(){
        System.out.println("user update...");
        return "{'module':'user update'}";
    }

    @RequestMapping
    @ResponseBody
    public String getById(){
        System.out.println("user getById...");
        return "{'module':'user getById'}";
    }

    @RequestMapping
    @ResponseBody
    public String getAll(){
        System.out.println("user getAll...");
        return "{'module':'user getAll'}";
    }
    */

It is worth noting that when we need to access and pass parameters through REST style, we need to add the @PathVariable Integer annotation in front of the formal parameters, and set the parameters of the access path to correspond to the formal parameters, such as: /users/{id} , corresponding to the formal parameter id. like:

@RequestMapping(value = "/users/{id}",method = RequestMethod.DELETE)
    @ResponseBody
    public String delete(@PathVariable Integer id){
        System.out.println("user delete..." + id);
        return "{'module':'user delete'}";
    }

3.Rest rapid development

It is a simplification of REST development

package com.itheima.controller;

import com.itheima.domain.Book;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

//@Controller
//@ResponseBody配置在类上可以简化配置，表示设置当前每个方法的返回值都作为响应体
//@ResponseBody
@RestController     //使用@RestController注解替换@Controller与@ResponseBody注解，简化书写
@RequestMapping("/books")
public class BookController {

//    @RequestMapping( method = RequestMethod.POST)
    @PostMapping        //使用@PostMapping简化Post请求方法对应的映射配置
    public String save(@RequestBody Book book){
        System.out.println("book save..." + book);
        return "{'module':'book save'}";
    }

//    @RequestMapping(value = "/{id}" ,method = RequestMethod.DELETE)
    @DeleteMapping("/{id}")     //使用@DeleteMapping简化DELETE请求方法对应的映射配置
    public String delete(@PathVariable Integer id){
        System.out.println("book delete..." + id);
        return "{'module':'book delete'}";
    }

//    @RequestMapping(method = RequestMethod.PUT)
    @PutMapping         //使用@PutMapping简化Put请求方法对应的映射配置
    public String update(@RequestBody Book book){
        System.out.println("book update..."+book);
        return "{'module':'book update'}";
    }

//    @RequestMapping(value = "/{id}" ,method = RequestMethod.GET)
    @GetMapping("/{id}")    //使用@GetMapping简化GET请求方法对应的映射配置
    public String getById(@PathVariable Integer id){
        System.out.println("book getById..."+id);
        return "{'module':'book getById'}";
    }

//    @RequestMapping(method = RequestMethod.GET)
    @GetMapping             //使用@GetMapping简化GET请求方法对应的映射配置
    public String getAll(){
        System.out.println("book getAll...");
        return "{'module':'book getAll'}";
    }
}

important point:

1.@RestController is equal to @ResponseBody+@Controller

2.@DeleteMapping("/{id}")等于@RequestMapping(value = "/{id}" ,method = RequestMethod.DELETE)

at last

This blog’s introduction to sprinmvc ends here. If this blog is helpful to you, please click a like to support it. Thank you! See you in the next blog!