SpringBoot整合PostgreSQL的示例代码

<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
    <version>3.0.4</version>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.26</version>
</dependency>

spring:
  datasource:
    driver-class-name: org.postgresql.Driver
    username: postgres
    password: root
    url: jdbc:postgresql://127.0.0.1:5432/postgres

@Slf4j
@SpringBootTest
class MypgApplicationTests {
    @Autowired
    JdbcTemplate jdbcTemplate;
    @Test
    void contextLoads() {
        Long count = jdbcTemplate.queryForObject("select count(*) from test", Long.class);
        log.info("记录总数：{}",count);
    }
}

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.3.0</version>
</dependency>

mybatis:
  mapper-locations: classpath:mapper/*.xml
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl 

@Data
public class Test {
    private Long id;
}

public interface TestMapper {
    Long queryForMybatis(Test testDO);
}

<?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.vainycos.dao.TestMapper">
    <select id="queryForMybatis" parameterType="com.vainycos.domain.Test" resultType="java.lang.Long">
        select count(*) from test
        <where>
            <if test="id != null and id != ''">
                and id = #{id}
            </if>
        </where>
    </select>
</mapper>

@Service
public class TestService {
    @Resource
    private TestMapper testMapper;
    public Long queryForMybatis(Test testDO){
        return testMapper.queryForMybatis(testDO);
    }
}

@MapperScan("com.vainycos.dao")
@SpringBootApplication
public class MypgApplication {
    public static void main(String[] args) {
        SpringApplication.run(MypgApplication.class, args);
    }
}

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.3</version>
</dependency>

public interface TestMapper extends BaseMapper<Test> {
    Long queryForMybatis(Test testDO);
}

public Long queryForMybatisPlus(Test testDO){
    Integer resultCount = testMapper.selectCount(new LambdaQueryWrapper<Test>()
            .eq(testDO.getId() != null, Test::getId, testDO.getId())
    );
    return resultCount.longValue();
}

@GetMapping("/queryForMybatisPlus")
public Long queryForMybatisPlus(Test testDO){
    return testService.queryForMybatisPlus(testDO);
}