3. Springboot configuration data source [Springboot]

  Springboot configuration data source

​ Spring Framework provides extensive support for SQL databases. From directly using JdbcTemplate for JDBC access to complete object relational mapping technology, such as Hibernate. Spring Data provides more levels of functionality, implemented directly from the Repository created by the interface, and uses conventions to generate queries from method names.

1、JDBC

1. Create a project and import the required dependencies

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
 		<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

2. Configure the data source

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://192.168.85.111:3306/sakila?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver

3. Test code

package com.mashibing;

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.Connection;
import java.sql.SQLException;

@SpringBootTest
class DataApplicationTests {

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
        System.out.println(dataSource.getClass());
        Connection connection = dataSource.getConnection();
        System.out.println(connection);
        connection.close();
    }

}
//可以看到默认配置的数据源为class com.zaxxer.hikari.HikariDataSource，我们没有经过任何配置，说明springboot默认情况下支持的就是这种数据源，可以在DataSourceProperties.java文件中查看具体的属性配置

4. Crud operation

​ 1. With a data source (com.zaxxer.hikari.HikariDataSource), then you can get a database connection (java.sql.Connection). With a connection, you can use the connection and native JDBC statements to operate the database

​ 2. Even if you do not use a third-party database operation framework, such as MyBatis, etc., Spring itself has done a lightweight package for native JDBC, namely org.springframework.jdbc.core.JdbcTemplate.

​ 3. All CRUD methods of database operations are in JdbcTemplate.

​ 4. Spring Boot not only provides a default data source, at the same time the JdbcTemplate has been configured by default and placed in the container, programmers only need to inject themselves to use

​ 5. The automatic configuration principle of JdbcTemplate is dependent on the org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration class under the org.springframework.boot.autoconfigure.jdbc package

package com.mashibing.contoller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
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;
import java.util.Map;

@RestController
public class JDBCController {

    @Autowired
    JdbcTemplate jdbcTemplate;

    @GetMapping("/emplist")
    public List<Map<String,Object>> empList(){
        String sql = "select * from emp";
        List<Map<String, Object>> maps = jdbcTemplate.queryForList(sql);
        return maps;
    }

    @GetMapping("/addEmp")
    public String addUser(){
        String sql = "insert into emp(empno,ename) values(1111,'zhangsan')";
        jdbcTemplate.update(sql);
        return "success";
    }

    @GetMapping("/updateEmp/{id}")
    public String updateEmp(@PathVariable("id") Integer id){
        String sql = "update emp set ename=? where empno = "+id;
        String name = "list";
        jdbcTemplate.update(sql,name);
        return "update success";
    }

    @GetMapping("/deleteEmp/{id}")
    public String deleteEmp(@PathVariable("id")Integer id){
        String sql = "delete from emp where empno = "+id;
        jdbcTemplate.update(sql);
        return "delete success";
    }
}

2. Custom data source DruidDataSource

View DataSourceAutoConfiguration.java through the source code

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
@EnableConfigurationProperties(DataSourceProperties.class)
@Import({ DataSourcePoolMetadataProvidersConfiguration.class, DataSourceInitializationConfiguration.class })
public class DataSourceAutoConfiguration {

	@Configuration(proxyBeanMethods = false)
	@Conditional(EmbeddedDatabaseCondition.class)
	@ConditionalOnMissingBean({ DataSource.class, XADataSource.class })
	@Import(EmbeddedDataSourceConfiguration.class)
	protected static class EmbeddedDatabaseConfiguration {

	}

	@Configuration(proxyBeanMethods = false)
	@Conditional(PooledDataSourceCondition.class)
	@ConditionalOnMissingBean({ DataSource.class, XADataSource.class })
	@Import({ DataSourceConfiguration.Hikari.class, DataSourceConfiguration.Tomcat.class,
			DataSourceConfiguration.Dbcp2.class, DataSourceConfiguration.Generic.class,
			DataSourceJmxConfiguration.class })
	protected static class PooledDataSourceConfiguration {

	}

	/**
	 * {@link AnyNestedCondition} that checks that either {@code spring.datasource.type}
	 * is set or {@link PooledDataSourceAvailableCondition} applies.
	 */
	static class PooledDataSourceCondition extends AnyNestedCondition {

		PooledDataSourceCondition() {
			super(ConfigurationPhase.PARSE_CONFIGURATION);
		}

		@ConditionalOnProperty(prefix = "spring.datasource", name = "type")
		static class ExplicitType {

		}

		@Conditional(PooledDataSourceAvailableCondition.class)
		static class PooledDataSourceAvailable {

		}

	}

1. Add druid's maven configuration

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.12</version>
</dependency>

2. Add the configuration of the data source

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://192.168.85.111:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource

3. The test found that the data source has been changed

4. Druid is a database connection pool, you can add a unique configuration of druid

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://192.168.85.111:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource
    #Spring Boot 默认是不注入这些属性值的，需要自己绑定
    #druid 数据源专有配置
    initialSize: 5
    minIdle: 5
    maxActive: 20
    maxWait: 60000
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true

    #配置监控统计拦截的filters，stat:监控统计、log4j：日志记录、wall：防御sql注入
    #如果允许时报错  java.lang.ClassNotFoundException: org.apache.log4j.Priority
    #则导入 log4j 依赖即可，Maven 地址： https://mvnrepository.com/artifact/log4j/log4j
    filters: stat,wall,log4j
    maxPoolPreparedStatementPerConnectionSize: 20
    useGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500

Test class, found that the configured parameters did not take effect

package com.mashibing;

import com.alibaba.druid.pool.DruidDataSource;
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.Connection;
import java.sql.SQLException;

@SpringBootTest
class DataApplicationTests {

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
        System.out.println(dataSource.getClass());
        Connection connection = dataSource.getConnection();
        System.out.println(connection);

        DruidDataSource druidDataSource = (DruidDataSource)dataSource;
        System.out.println(druidDataSource.getMaxActive());
        System.out.println(druidDataSource.getInitialSize());
        connection.close();
    }

}

Need to define the configuration class of druidDatasource and bind parameters

package com.mashibing.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
public class DruidConfig {
    @ConfigurationProperties(prefix = "spring.datasource")
    @Bean
    public DataSource druidDataSource(){
        return new DruidDataSource();
    }
}

Druid data sources also have monitoring functions and provide a web interface for users to view.

Add log4j log dependency

        <!-- https://mvnrepository.com/artifact/log4j/log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

Add code to DruidConfig to configure the servlet of the druid monitoring management console

package com.mashibing.config;

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.support.http.StatViewServlet;
import com.alibaba.druid.support.http.WebStatFilter;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.servlet.Servlet;
import javax.sql.DataSource;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

@Configuration
public class DruidConfig {
    @ConfigurationProperties(prefix = "spring.datasource")
    @Bean
    public DataSource druidDataSource(){
        return new DruidDataSource();
    }

    @Bean
    public ServletRegistrationBean druidServletRegistrationBean(){
        ServletRegistrationBean<Servlet> servletRegistrationBean = new ServletRegistrationBean<>(new StatViewServlet(),"/druid/*");
        Map<String,String> initParams = new HashMap<>();
        initParams.put("loginUsername","admin");
        initParams.put("loginPassword","123456");
        //后台允许谁可以访问
        //initParams.put("allow", "localhost")：表示只有本机可以访问
        //initParams.put("allow", "")：为空或者为null时，表示允许所有访问
        initParams.put("allow","");
        //deny：Druid 后台拒绝谁访问
        //initParams.put("msb", "192.168.1.20");表示禁止此ip访问

        servletRegistrationBean.setInitParameters(initParams);
        return servletRegistrationBean;
    }

    //配置 Druid 监控 之  web 监控的 filter
    //WebStatFilter：用于配置Web和Druid数据源之间的管理关联监控统计
    @Bean
    public FilterRegistrationBean webStatFilter() {
        FilterRegistrationBean bean = new FilterRegistrationBean();
        bean.setFilter(new WebStatFilter());

        //exclusions：设置哪些请求进行过滤排除掉，从而不进行统计
        Map<String, String> initParams = new HashMap<>();
        initParams.put("exclusions", "*.js,*.css,/druid/*");
        bean.setInitParameters(initParams);

        //"/*" 表示过滤所有请求
        bean.setUrlPatterns(Arrays.asList("/*"));
        return bean;
    }
}

3. Springboot configures multiple data sources and switches dynamically

​ DataSource is bound to the thread, the configuration of the dynamic data source is mainly achieved by inheriting the AbstractRoutingDataSource class, and the protected Object determineCurrentLookupKey() method in the AbstractRoutingDataSource class is implemented to obtain the data source, so we need to create a multi-threaded thread data first Isolate the class to store the DataSource, and then use this class to obtain the DataSource of the current thread in the determineCurrentLookupKey() method. In the AbstractRoutingDataSource class, the DataSource is stored by Key-value. We can store the Key through ThreadLocal to achieve data Dynamic switching of sources.

1. Modify the configuration file class

spring:
  datasource:
    local:
      username: root
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver
      jdbc-url: jdbc:mysql://localhost:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    remote:
      username: root
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver
      jdbc-url: jdbc:mysql://192.168.85.111:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8

2. Create a data source enumeration class

package com.mashibing.mult;

public enum DataSourceType {
    REMOTE,
    LOCAL
}

3. Data source switching processing

​ Create a data source switching processing class, which has methods for obtaining, setting and condition of data source variables, among which threadlocal is used to save a thread shared variable.

package com.mashibing.mult;

public class DynamicDataSourceContextHolder {

    /**
     * 使用ThreadLocal维护变量，ThreadLocal为每个使用该变量的线程提供独立的变量副本，
     *  所以每一个线程都可以独立地改变自己的副本，而不会影响其它线程所对应的副本。
     */
    private static final ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();

    /**
     * 设置数据源变量
     * @param dataSourceType
     */
    public static void setDataSourceType(String dataSourceType){
        System.out.printf("切换到{%s}数据源", dataSourceType);
        CONTEXT_HOLDER.set(dataSourceType);
    }

    /**
     * 获取数据源变量
     * @return
     */
    public static String getDataSourceType(){
        return CONTEXT_HOLDER.get();
    }

    /**
     * 清空数据源变量
     */
    public static void clearDataSourceType(){
        CONTEXT_HOLDER.remove();
    }
}

4. Inherit AbstractRoutingDataSource

​ The dynamic switching of data sources mainly relies on AbstractRoutingDataSource. Create a subclass of AbstractRoutingDataSource and override the determineCurrentLookupKey method to determine which data source to use. The two properties of AbstractRoutingDataSource, defaultTargetDataSource and targetDataSources, are mainly used here. defaultTargetDataSource default target data source, targetDataSources (map type) store the data source used to switch.

package com.mashibing.mult;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import javax.sql.DataSource;
import java.util.Map;

public class DynamicDataSource extends AbstractRoutingDataSource {

    public DynamicDataSource(DataSource defaultTargetDataSource, Map<Object, Object> targetDataSources) {
        super.setDefaultTargetDataSource(defaultTargetDataSource);
        super.setTargetDataSources(targetDataSources);
        // afterPropertiesSet()方法调用时用来将targetDataSources的属性写入resolvedDataSources中的
        super.afterPropertiesSet();
    }

    /**
     * 根据Key获取数据源的信息
     *
     * @return
     */
    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicDataSourceContextHolder.getDataSourceType();
    }
}

5. Inject the data source

package com.mashibing.mult;

import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

@Configuration
public class DataSourceConfig {
    @Bean
    @ConfigurationProperties("spring.datasource.remote")
    public DataSource remoteDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.local")
    public DataSource localDataSource() {
        return DataSourceBuilder.create().build();
    }
    
    @Bean(name = "dynamicDataSource")
    @Primary
    public DynamicDataSource dataSource(DataSource remoteDataSource, DataSource localDataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceType.REMOTE.name(), remoteDataSource);
        targetDataSources.put(DataSourceType.LOCAL.name(), localDataSource);
        return new DynamicDataSource(remoteDataSource, targetDataSources);
    }
}

6. Customize multiple data source switch annotations

​ Set the annotation of the intercepted data source, which can be set on a specific class or on a specific method

package com.mashibing.mult;

import java.lang.annotation.*;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {
    /**
     * 切换数据源名称
     */
    DataSourceType value() default DataSourceType.REMOTE;
}

7, the realization of AOP interception class

​ By intercepting the above annotation, processing the data source information of the currently executed SQL before its execution, the data source information in CONTEXT_HOLDER.set(dataSourceType) is obtained from the annotations we set, if not set, the default data is used Source information.

package com.mashibing.mult;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

@Aspect
@Order(1)
@Component
public class DataSourceAspect {

    @Pointcut("@annotation(com.mashibing.mult.DataSource)")
    public void dsPointCut() {

    }

    @Around("dsPointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Method method = signature.getMethod();
        DataSource dataSource = method.getAnnotation(DataSource.class);
        if (dataSource != null) {
            DynamicDataSourceContextHolder.setDataSourceType(dataSource.value().name());
        }
        try {
            return point.proceed();
        } finally {
            // 销毁数据源 在执行方法之后
            DynamicDataSourceContextHolder.clearDataSourceType();
        }
    }
}

8. Use switch data source annotation

package com.mashibing.mult;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;
import java.util.Map;


@RestController
public class EmpController {

    @Autowired
    JdbcTemplate jdbcTemplate;

    @GetMapping("/local")
    @DataSource(value = DataSourceType.LOCAL)
    public List<Map<String, Object>> local(){
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("select * from emp");
        return maps;
    }
    @GetMapping("/remote")
    @DataSource(value = DataSourceType.REMOTE)
    public List<Map<String, Object>> remote(){
        List<Map<String, Object>> maps = jdbcTemplate.queryForList("select * from emp");
        return maps;
    }

}

9. In the process of starting the project, the problem of circular dependency will occur, just modify the startup class directly

package com.mashibing;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;

@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
public class SpringbootDataApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootDataApplication.class, args);
    }
}

4. Springboot integrates mybatis

1. Import the dependencies of mybatis

<!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

2. Configure the data source

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://192.168.85.111:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver

3. Testing

package com.mashibing;

import com.alibaba.druid.pool.DruidDataSource;
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.Connection;
import java.sql.SQLException;

@SpringBootTest
class DataApplicationTests {

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
        System.out.println(dataSource.getClass());
        Connection connection = dataSource.getConnection();
        System.out.println(connection);
        System.out.println(connection.getMetaData().getURL());

        connection.close();
    }
}

4. Create an entity class

package com.mashibing.entity;

import java.sql.Date;
import java.util.Objects;

public class Emp {
    private Integer empno;
    private String ename;
    private String job;
    private Integer mgr;
    private Date hiredate;
    private Double sal;
    private Double comm;
    private Integer deptno;

    public Emp() {
    }

    public Emp(Integer empno, String ename) {
        this.empno = empno;
        this.ename = ename;
    }

    public Emp(Integer empno, String ename, String job, Integer mgr, Date hiredate, Double sal, Double comm, Integer deptno) {
        this.empno = empno;
        this.ename = ename;
        this.job = job;
        this.mgr = mgr;
        this.hiredate = hiredate;
        this.sal = sal;
        this.comm = comm;
        this.deptno = deptno;
    }

    public Integer getEmpno() {
        return empno;
    }

    public void setEmpno(Integer empno) {
        this.empno = empno;
    }

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

    public Integer getMgr() {
        return mgr;
    }

    public void setMgr(Integer mgr) {
        this.mgr = mgr;
    }

    public Date getHiredate() {
        return hiredate;
    }

    public void setHiredate(Date hiredate) {
        this.hiredate = hiredate;
    }

    public Double getSal() {
        return sal;
    }

    public void setSal(Double sal) {
        this.sal = sal;
    }

    public Double getComm() {
        return comm;
    }

    public void setComm(Double comm) {
        this.comm = comm;
    }

    public Integer getDeptno() {
        return deptno;
    }

    public void setDeptno(Integer deptno) {
        this.deptno = deptno;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Emp)) return false;
        Emp emp = (Emp) o;
        return Objects.equals(empno, emp.empno) &&
                Objects.equals(ename, emp.ename) &&
                Objects.equals(job, emp.job) &&
                Objects.equals(mgr, emp.mgr) &&
                Objects.equals(hiredate, emp.hiredate) &&
                Objects.equals(sal, emp.sal) &&
                Objects.equals(comm, emp.comm) &&
                Objects.equals(deptno, emp.deptno);
    }

    @Override
    public int hashCode() {

        return Objects.hash(empno, ename, job, mgr, hiredate, sal, comm, deptno);
    }

    @Override
    public String toString() {
        return "Emp{" +
                "empno=" + empno +
                ", ename='" + ename + '\'' +
                ", job='" + job + '\'' +
                ", mgr=" + mgr +
                ", hiredate=" + hiredate +
                ", sal=" + sal +
                ", comm=" + comm +
                ", deptno=" + deptno +
                '}';
    }
}

5. Configure the Mapper interface class

package com.mashibing.mapper;

import com.mashibing.entity.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface EmpMapper {

    List<Emp> selectEmp();

    Emp selectEmpById(Integer empno);

    Integer addEmp(Emp emp);

    Integer updateEmp(Emp emp);

    Integer deleteEmp(Integer empno);
}

6. Create an Emp.xml file under resources

<?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.mashibing.mapper.EmpMapper">

    <select id="selectEmp" resultType="Emp">
    select * from emp
  </select>

    <select id="selectEmpById" resultType="Emp">
    select * from emp where empno = #{empno}
    </select>

    <insert id="addEmp" parameterType="Emp">
    insert into emp (empno,ename) values (#{empno},#{ename})
    </insert>

    <update id="updateEmp" parameterType="Emp">
    update emp set ename=#{ename} where empno = #{empno}
    </update>

    <delete id="deleteEmp" parameterType="int">
    delete from emp where empno = #{empno}
</delete>
</mapper>

7. Add configuration file

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://192.168.85.111:3306/demo?serverTimezone=UTC&useUnicode=true@characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
mybatis:
  mapper-locations: classpath:mybatis/mapper/*.xml
  type-aliases-package: com.mashibing.entity

8. Write the controller

package com.mashibing.contoller;

import com.mashibing.entity.Emp;
import com.mashibing.mapper.EmpMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class EmpController {
    @Autowired
    private EmpMapper empMapper;

    //选择全部用户
    @GetMapping("/selectEmp")
    public String selectEmp(){
        List<Emp> emps = empMapper.selectEmp();
        for (Emp Emp : emps) {
            System.out.println(Emp);
        }
        return "ok";
    }
    //根据id选择用户
    @GetMapping("/selectEmpById")
    public String selectEmpById(){
        Emp emp = empMapper.selectEmpById(1234);
        System.out.println(emp);
        return "ok";
    }
    //添加一个用户
    @GetMapping("/addEmp")
    public String addEmp(){
        empMapper.addEmp(new Emp(1234,"heheda"));
        return "ok";
    }
    //修改一个用户
    @GetMapping("/updateEmp")
    public String updateEmp(){
        empMapper.updateEmp(new Emp(1234,"heihei"));
        return "ok";
    }
    //根据id删除用户
    @GetMapping("/deleteEmp")
    public String deleteEmp(){
        empMapper.deleteEmp(1234);
        return "ok";
    }
}

9. Just test