建立项目

spring: application: name: child-project # 名称 datasource: type: com.alibaba.druid.pool.DruidDataSource # 数据源类型 driver-class-name: com.mysql.cj.jdbc.Driver # 数据库驱动包 url: jdbc:mysql://127.0.0.1:3306/irscloud?useSSL=false&characterEncoding=utf8&useUnicode=true username: … password: …

mybatis: mapper-locations: classpath:mapper/*.xml type-aliases-package: com.ilirus.springcloud.entities # entity别名类所在的package

</details>

### 创建启动类
在子工程的`src/main/java/<groupId>`目录下创建对应的启动类
<details><summary>点击展开</summary>```java
package com.ilirus.springcloud;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import java.io.Serializable;

@Data @AllArgsConstructor @NoArgsConstructor public class Payment implements Serializable { private Long id; private String serial; }

返回给前端的Result类
```java
package com.ilirus.springcloud.entities;

import com.ilirus.springcloud.enums.Status;
import org.jetbrains.annotations.Contract;
import org.jetbrains.annotations.NotNull;

public class CommonResult<T> {
    private Integer code;
    private String message;
    private T data;

    @NotNull
    @Contract("_ -> new")
    public static<T> CommonResult<T> Of(@NotNull Status status) {
        return new CommonResult<T>(status.getCode(), status.getMessage());
    }

    @NotNull
    @Contract("_, _ -> new")
    public static<T> CommonResult<T> OfData(@NotNull Status status, T data) {
        return new CommonResult<T>(status.getCode(), status.getMessage(), data);
    }

    private CommonResult(Integer code, String message) {
        this(code, message, null);
    }

    private CommonResult(Integer code, String message, T data) {
        this.code = code;
        this.message = message;
        this.data = data;
    }

    public Integer getCode() {
        return this.code;
    }

    public String getMessage() {
        return this.message;
    }

    public T getData() {
        return this.data;
    }
}

import org.jetbrains.annotations.Contract;

public enum Status { SUCCESS(200,“sucess”), FAIL(400,“fail”), NO_DATA_FOUND(404,“not found”) ;

private Integer code;
private String message;

Status(Integer code, String message) {
    this.code = code;
    this.message = message;
}

@Contract(pure = true)
public Integer getCode() {
    return code;
}

@Contract(pure = true)
public String getMessage() {
    return message;
}

}

</details>

### 编写Dao
<details><summary>点击展开</summary>```java
package com.ilirus.springcloud.dao;

import com.ilirus.springcloud.entities.Payment;
import org.apache.ibatis.annotations.Param;

import java.util.Optional;

public interface PaymentDao {
    public Optional<Payment> getPaymentByID(@Param("id") Long id);

    public int createPayment(Payment payment);
}

mapper文件

<?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.ilirus.springcloud.dao.PaymentDao">

  <resultMap id="BaseResultMap" type="com.ilirus.springcloud.entities.Payment">
    <id column="id" property="id" jdbcType="BIGINT"/>
    <id column="serial" property="serial" jdbcType="VARCHAR"/>
  </resultMap>
  <select id="getPaymentByID" parameterType="Long" resultMap="BaseResultMap">
    select id, serial from payment where id=#{id} limit 1;
  </select>

  <insert id="createPayment" parameterType="Payment" useGeneratedKeys="true" keyProperty="id">
    insert into payment(serial) values(#{serial});
  </insert>

</mapper>

import com.ilirus.springcloud.entities.Payment; import org.apache.ibatis.annotations.Param;

public interface PaymentService { public Payment getPaymentByID(@Param(“id”) Long id);

public int createPayment(Payment payment);

}

实现类
```java
package com.ilirus.springcloud.service.impl;

import com.ilirus.springcloud.dao.PaymentDao;
import com.ilirus.springcloud.entities.Payment;
import com.ilirus.springcloud.service.PaymentService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;

@Service
public class PaymentServiceImpl implements PaymentService {
    @Resource
    private PaymentDao paymentDao;

    @Override
    public Payment getPaymentByID(Long id) throws NullPointerException {
        return paymentDao.getPaymentByID(id).orElse(null);
    }

    @Override
    public int createPayment(Payment payment) {
        return paymentDao.createPayment(payment);
    }
}

import com.ilirus.springcloud.entities.CommonResult; import com.ilirus.springcloud.entities.Payment; import com.ilirus.springcloud.enums.Status; import com.ilirus.springcloud.service.PaymentService; import lombok.extern.slf4j.Slf4j; import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController @RequestMapping("/payment") @Slf4j public class PaymentController { @Resource private PaymentService paymentService;

@PostMapping("/create")
public CommonResult create(@RequestBody Payment payment) {
    int res = paymentService.createPayment(payment);
    log.info("插入结果: "+res);

    if(res > 0) {
        return CommonResult.Of(Status.SUCCESS);
    } else {
        return CommonResult.Of(Status.FAIL);
    }
}

@GetMapping("/query/{id}")
public CommonResult queryByID(@PathVariable("id") Long id) {
    Payment payment = paymentService.getPaymentByID(id);
    if(payment != null) {
        return CommonResult.OfData(Status.SUCCESS, payment);
    } else {
        return CommonResult.Of(Status.NO_DATA_FOUND);
    }
}

}

</details>

### 编写测试
在子工程的`src/test/java/<groupId>`目录下创建对应的测试类
<details><summary>点击展开</summary>```java
package com.ilirus.springcloud;

import com.ilirus.springcloud.entities.Payment;
import com.ilirus.springcloud.service.PaymentService;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.annotation.Rollback;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.sql.SQLException;
import java.time.Duration;

@SpringBootTest
class ChildProjectTest {
    @Resource
    PaymentService paymentService;

    @BeforeEach
    void echo() {
        System.out.println("====Test Start====");
    }

    @AfterAll
    static void done() {
        System.out.println("====Test Done.====");
    }

    @Test
    void checkQuery() {
        Payment payment = paymentService.getPaymentByID(1L);
        Assertions.assertNotNull(payment);
    }

    @Test
    @Transactional
    @Rollback
    void checkCreate() throws SQLException {
        Payment payment = new Payment();
        payment.setSerial("test");
        int res = paymentService.createPayment(payment);
        System.out.println(res);
        Assertions.assertNotEquals(res, 0);

        Assertions.assertThrows(SQLException.class, () -> {
            ...
        });
        Assertions.assertTimeout(Duration.ofSeconds(3), () -> {
            ...
        });
    }
}