Getting started with Springboot

Springboot

The biggest feature of Springboot is automatic assembly

JSR303 data verification

1.举个栗子春暖花开
@Component  //组件，方便springboot自动配置
@ConfigurationProperties(prefix = "person")  //给实体类赋值
@Validated //数据验证
public class Person {
    
    
    @Email(message="邮箱格式错误")
    private String name; //name必须是邮箱格式
}
2.数据校验常见参数
@NotNull(message="名字不能为空")
private String userName;
@Max(value=120,message="年龄最大不能查过120")
private int age;
@Email(message="邮箱格式错误")
private String email;

空检查
@Null       验证对象是否为null
@NotNull    验证对象是否不为null, 无法查检长度为0的字符串
@NotBlank   检查约束字符串是不是Null还有被Trim的长度是否大于0,只对字符串,且会去掉前后空格.
@NotEmpty   检查约束元素是否为NULL或者是EMPTY.

Booelan检查
@AssertTrue     验证 Boolean 对象是否为 true  
@AssertFalse    验证 Boolean 对象是否为 false  

长度检查
@Size(min=, max=) 验证对象（Array,Collection,Map,String）长度是否在给定的范围之内  
@Length(min=, max=) string is between min and max included.

日期检查
@Past       验证 Date 和 Calendar 对象是否在当前时间之前  
@Future     验证 Date 和 Calendar 对象是否在当前时间之后  
@Pattern    验证 String 对象是否符合正则表达式的规则

Principles of automatic assembly

SpringBoot startup will load a large number of automatic configuration classes
Let's see if the functions we need are in the automatic configuration classes written by SpringBoot by default
Let's look at which components are configured in this automatic configuration class (as long as the components we want to use exist in them, we don't need to configure them manually)

When adding components to the auto-configuration class in the container, certain properties are obtained from the properties class. We only need to specify the values of these properties in the configuration file

xxxxAutoConfigurartion: Automatic configuration class to add components to the container
xxxxProperties: The relevant properties in the package configuration file have a one-to-one correspondence with our application.yml file to configure
Give a chestnut spring blossoms

@ConfigurationProperties(prefix = "server")
public class ServerProperties {
      
      
    private Integer port;
    //...
}
首先在autoconfigure文件下的META-INF里找到spring.factories文件
HttpEncodingAutoConfiguration-----------------ServerProperties-----------------server
所以我们才可以在application.yml文件中使用server.port
我们也可以通过在application.yml文件中写入debug=true 从而知道哪些自动配置类生效

A simple web project

1. Home page configuration
- The static resources of all pages need to be taken over by thymeleaf
2. Page internationalization
- We need to configure the i18n file name to not change
- If we need to automatically switch buttons in the project, we need to customize a componentLocaleResolver
- Remember to configure the components you wrote to the spring container @bean
3. Login + interceptor
4. Add, delete, modify and check
- Employee list display
  - Extract public pages and place them in the commons folder
    - extract:th:fragment="sidebar"
    - insert:th:replace="~{commons/commons::sidebar(active='main.html')}
      - Insert can use replace or insert
      - (active='main.html') is the equivalent of passing parameters during the insertion process? active='main.html' This may ensure that the label is highlighted
  - List loop display
- Add employee
  - Button submit
  - Jump to add page
  - Added employee successfully
  - Back to homepage

Springboot integrates Mybatis

Import the dependencies required by MyBatis

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

Configure database connection information and integrate mybatis configuration

spring:
  datasource:
    username: root
    password: 123qwe
    #?serverTimezone=UTC解决时区的报错
    url: jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.cj.jdbc.Driver
#整合mybatis
mybatis:
  type-aliases-package: com.kuang.pojo
  mapper-locations: classpath:mybatis/mapper/*.xml

Test whether the database connection is successful

package com.kuang;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import javax.sql.DataSource;
import java.sql.SQLException;

@SpringBootTest
class Springboot03ApplicationTests {
    
    

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
    
    
        System.out.println(dataSource);
        System.out.println(dataSource.getConnection());
    }
}

Create entity class

package com.kuang.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Department {
    
    

    private Integer id;
    private String departmentName;

}

DAO layer (Mapper interface)

package com.kuang.mapper;

import com.kuang.pojo.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

//这个注解表示了这是一个mybatis的mapper类
@Mapper
@Repository
public interface UserMapper {
    
    
    List<User> queryUserList();

    User queryUserById(int id);

    int addUser(User user);

    int deleteUser(int id);
}

Interface implementation classes (Mapper mapping files) are generally placed in the resources directory

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.kuang.mapper.UserMapper">
    <select id="queryUserList" resultType="User">
        select * from user;
    </select>
    <select id="queryUserById" resultType="User">
        select * from user where id=#{
    
    id};
    </select>
    <insert id="addUser" parameterType="User">
        insert into user(id,name,pwd) values(#{
    
    id},#{
    
    name},#{
    
    pwd});
    </insert>
    <delete id="deleteUser" parameterType="int">
        delete from user where id=#{
    
    id};
    </delete>
</mapper>

controller class

package com.kuang.controller;

import com.kuang.mapper.UserMapper;
import com.kuang.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class UserController {
    
    
    @Autowired
    private UserMapper userMapper;
    @GetMapping("/queryUserList")
    public List<User> queryUserList(){
    
    
        List<User> userList=userMapper.queryUserList();
        return userList;
    }
    @GetMapping("/queryUserById/{id}")
    public User queryUserById(@PathVariable("id") int id){
    
    
        User user=userMapper.queryUserById(id);
        return user;
    }
    @GetMapping("/addUser")
    public String addUser(){
    
    
        userMapper.addUser(new User(8,"阿毛","423562"));
        return "add ok";
    }
    @GetMapping("/deleteUser")
    private String deleteUser(){
    
    
        userMapper.deleteUser(8);
        return "delete ok";
    }
}

test
- Request in the browserhttp:localhost/8080/queryUserList

to sum up

If you plan to use Springboot+mybatis for your project in the short term, then you can master how to use this framework (it's actually very simple).
- Recommended video station B: Mad God said
- The recommended method is 1.5 times faster. If you encounter the key, you can slow down and you can skip the source code explanation.
If you are going to be engaged in java back-end development in the future, it is recommended to look at the source code, see the official documents, do your own summary, and participate in some forums.

[Springboot] basic framework learning