Springboot-mybatis realizes addition, deletion, modification and query (1)

1. springboot integrates mybatis environment

1. Create a springboot project.
   initial directory structure
   

2. Introduce dependencies in pom.xml (note refresh after adding)
   first introduce mybatis-springboot integration dependencies, database drivers, and database connection pools.
   Add it within the tag of the pom.xml file <dependencies>.

		<!--mybatis和springboot整合的依赖-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.3</version>
        </dependency>
        
        <!--连接mysql,数据库驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        
        <!--数据库连接池-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.4</version>
        </dependency>

In addition, you can use the lombok plug-in, which can help us simplify the code through simple annotations, and let lombok automatically generate default getter/setter methods. Written in dependencies.

		<!--lombok插件-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

3. Build a package (new package)
   to build a dao layer under the src/main/java/personal folder
   : for data access
   pojo: to build an entity class (the entity class in java corresponds to a table in the database)
   controller: the control layer
   service: Call the dao layer to realize the operation on the database

4. Create an entity class
   Create an entity class (class) User in the pojo layer, which implements a User table

5. Database connection
   After creating the User class here, you can connect to the database to see what fields there are.
   Method: idea Click Database on the far right sidebar, click the plus sign, enter the user name and password, link to the database, and test the connection. If it is a database linked to a remote server, change the localhost and port number to the server address and port.
   
   Then select a data table
   
   The mybatis data table selected here is created in advance, and a piece of user information is stored in it, including id, name, and pwd.
   

6. pojo/User.java
   Return to the class in Section 4. The attributes of the entity class in Java are in one-to-one correspondence with the fields of the database.

public class User {
    
    
	private Integer id;
	private String name;
	private String pwd;
	private String perm;
}

Then outside the public

@Data
@AllArgsConstructor
//有参构造
@NoArgsConstructor
//无参构造
public class User {
    
    
	private Integer id;
	private String name;
	private String pwd;
	private String perm;
}

It uses lombok to directly build methods with parameters, without parameters, get, set, tostring, etc.

The entity class has been successfully built here.

7. The configuration of the configuration file (src/resources/application.yml)
   
   looks at the database version here;
   when integrating mybatis, create a new mybatis folder under resources to store all *.xml files, and then configuremapper-locations: classpath:/mybatis/*.xml

#端口
server:
  port: 8083

#数据库的驱动和url.
#url中的serverTimezone是对数据库时区的设置，8.0以上版本需要加入，而且8.0以后的mysql版本需要加入driver-class-name
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    username: root
    password: 123456
    url: jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT
    driver-class-name: com.mysql.cj.jdbc.Driver


#mybatis环境搭建.type-aliases-package是选择包，
mybatis:
  type-aliases-package: lzy.springbootuser.pojo  #别名
  mapper-locations: classpath:/mybatis/*.xml   #xml文件

Here the springboot integration mybatis environment ends.