Springcloud入門父工程創建&訂單模塊&支付模塊開發

　　開始學習springcloud，用到的主要是Spingboot+MabatisPlus + SpringdataJPA(這個是為了建表方便)。

1.父工程創建

1. 創建工程

創建maven骨架，類型選擇：maven-archetype-site，JDK版本選擇1.8。

 2.設置文件編碼、注解生效以及過濾的文件

字符編碼設置：

注解允許：

 JDK編譯選擇8：

 選擇過濾文件：(過濾掉不必要的文件)

 3. 父工程pom文件編寫

可以刪除src目錄，之后編寫pom.xml：

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.qz.cloud</groupId>
    <artifactId>cloud</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <!-- 統一管理jar包版本 -->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <junit.version>4.12</junit.version>
        <log4j.version>1.2.17</log4j.version>
        <lombok.version>1.16.18</lombok.version>
        <mybatispuls.spring.boot.version>2.3</mybatispuls.spring.boot.version>
        <jpa.version>2.3.1.RELEASE</jpa.version>
        <mysql.version>5.1.47</mysql.version>
        <druid.version>1.1.16</druid.version>
    </properties>

    <!-- 子模塊繼承之后，提供作用：鎖定版本+子modlue不用寫groupId和version  -->
    <dependencyManagement>
        <dependencies>
            <!--spring boot 2.2.2-->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.2.2.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <!--spring cloud Hoxton.SR1-->
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Hoxton.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <!--spring cloud alibaba 2.1.0.RELEASE-->
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>2.1.0.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>${mysql.version}</version>
            </dependency>
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid</artifactId>
                <version>${druid.version}</version>
            </dependency>
            <!-- spring-boot整合mybatis-plus -->
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>${mybatispuls.spring.boot.version}</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>${junit.version}</version>
            </dependency>
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>${log4j.version}</version>
            </dependency>
            <!-- springdata jpa依賴 -->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
                <version>${jpa.version}</version>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${lombok.version}</version>
                <optional>true</optional>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <addResources>true</addResources>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

這里需要注意：

(1)父工程的packagin是pom，用於父工程聚合。

(2)dependencyManagement和dependencies的區別：

dependencyManagement 通常用於項目最頂層的父pom文件。能讓所有子項目引用一個依賴而不用顯示的列出版本號。

maven子項目如果寫了版本號和scope會用自己的，如果沒寫，會沿着父子層向上走，直到找到擁有一個dependencyManagement元素的項目，然后使用此項目的version和scope。

這樣做的好處是版本便於管理，比如想要升級個jar包只需要在父類統一升級即可。

另外，dependencyManagement只是聲明依賴，不實現引入，因此子項目需要顯示的聲明所用的依賴。

2. 支付模塊構建

　　支付模塊使用8081端口。

1.新建moudle

選擇父工程之后新建moudle，GroupId和Version采用繼承的即可，如下：

(1) 新建完成之后查看父pom.xml文件會多了modules配置並引入新建的moudle。

(2)新的payment模塊的pom文件只有artifactId，沒有G和A，會采用父類的G和A。

2.修改pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud</artifactId>
        <groupId>cn.qz.cloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>cloud-provider-payment8081</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!-- spring-boot整合mybatis-plus -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.10</version>
        </dependency>
        <!--mysql-connector-java-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--jdbc-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <!-- springdata jpa依賴 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>


</project>

3.修改application.yml

server:
  port: 8081

spring:
  application:
    name: cloud-payment-service
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource            # 當前數據源操作類型
    driver-class-name: org.gjt.mm.mysql.Driver              # mysql驅動包
    url: jdbc:mysql://localhost:3306/cloud?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: 123456
  jpa:
    showSql: true
    hibernate.ddlAuto: update
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect

mybatis-plus:
  mapperLocations: classpath:mapper/*.xml
  type-aliases-package: cn.qz.cloud.bean    # 所有Entity別名類所在包

這里需要注意到mysql數據庫建立對應的database。

4. 編寫啟動類

package cn.qz.cloud;

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

/**
 * @Author: qlq
 * @Description
 * @Date: 22:24 2020/9/24
 */
@SpringBootApplication
public class PaymentMain8081 {
    public static void main(String[] args) {
        SpringApplication.run(PaymentMain8081.class, args);
    }
}

5.編寫業務代碼

(0)一個簡單的返回JSON的工具類

package cn.qz.cloud.utils;

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

import java.io.Serializable;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class JSONResultUtil<T> implements Serializable {

    private static final long serialVersionUID = 3637122497350396679L;

    private boolean success;

    private String code;

    private String msg;

    private T data;

    public static <T> JSONResultUtil<T> success() {
        return new JSONResultUtil<>(true, "200", "", null);
    }

    public static <T> JSONResultUtil<T> successWithData(T data) {
        return new JSONResultUtil<>(true, "200", "", data);
    }

    public static <T> JSONResultUtil<T> error(String codeOrMsg) {
        return errorWithData(codeOrMsg, null);
    }

    public static <T> JSONResultUtil<T> errorWithMsg(String errorCode, String msg) {
        return new JSONResultUtil<T>(false, errorCode, msg, null);
    }

    public static <T> JSONResultUtil<T> errorWithData(String codeOrMsg, T data) {
        return new JSONResultUtil<T>(false, codeOrMsg, codeOrMsg, data);
    }
}

(1)bean對象：

package cn.qz.cloud.bean;

import com.baomidou.mybatisplus.annotations.TableField;
import com.baomidou.mybatisplus.annotations.TableId;
import com.baomidou.mybatisplus.enums.IdType;
import lombok.Getter;
import lombok.Setter;
import org.hibernate.annotations.Index;

import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
import java.util.Date;

/**
 * 所有實體類中相同的部分(自增ID類型的)
 *
 * @author Administrator
 */
@MappedSuperclass
@Getter
@Setter
public abstract class AbstractSequenceEntity {

    private static final long serialVersionUID = -674790161451253326L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @TableId(type = IdType.AUTO) // 增加該注解，mybatis plus insert之后會給bean設上Id
    protected Long id;

    /**
     * 創建時間
     */
    @Index(name = "createtime")
    @TableField(update = "%s") // 增加該注解，MP修改的時候不會修改該值
    protected Date createtime;

    public AbstractSequenceEntity() {
        this.createtime = new Date();
    }
}

payment類：

package cn.qz.cloud.bean;

import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import javax.persistence.Entity;

/**
 * @Author: qlq
 * @Description
 * @Date: 22:37 2020/9/24
 */
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
@Getter
@Setter
@Entity
public class Payment extends AbstractSequenceEntity {

    private String serial;
}

(2)mapper-繼承MP的BaseMapper

package cn.qz.cloud.mapper;

import cn.qz.cloud.bean.Payment;
import com.baomidou.mybatisplus.mapper.BaseMapper;
import org.apache.ibatis.annotations.Mapper;

/**
 * @Author: qlq
 * @Description
 * @Date: 14:30 2020/9/25
 */
@Mapper
public interface PaymentMapper extends BaseMapper<Payment> {
}

(3)service

接口繼承MP的IService：

package cn.qz.cloud.service;

import cn.qz.cloud.bean.Payment;
import com.baomidou.mybatisplus.service.IService;

/**
 * @Author: qlq
 * @Description
 * @Date: 14:31 2020/9/25
 */
public interface PaymentService extends IService<Payment>{
}

實現類繼承MP的serviceImpl

package cn.qz.cloud.service;

import cn.qz.cloud.bean.Payment;
import cn.qz.cloud.mapper.PaymentMapper;
import com.baomidou.mybatisplus.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;

/**
 * @Author: qlq
 * @Description
 * @Date: 14:31 2020/9/25
 */
@Service
public class PaymentServiceImpl extends ServiceImpl<PaymentMapper, Payment> implements PaymentService {
}

(4)controller

抽象類：

package cn.qz.cloud.controller;

import cn.qz.cloud.utils.JSONResultUtil;
import com.baomidou.mybatisplus.service.IService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.*;

import java.io.Serializable;
import java.util.List;
import java.util.Map;

/**
 * @param <T>
 * @param <E>
 */
@RestController
@Slf4j
public abstract class AbstractController<T, E extends Serializable> {

    public abstract IService<T> getBaseService();

    @PostMapping("/save")
    public JSONResultUtil<Object> save(@RequestBody T bean) {
        boolean insert = getBaseService().insert(bean);
        if (insert) {
            return JSONResultUtil.successWithData(bean);
        }

        return JSONResultUtil.error("添加失敗");
    }

    @PostMapping("/delete/{id}")
    public JSONResultUtil<Object> delete(@PathVariable() E id) {
        boolean result = getBaseService().deleteById(id);
        if (result) {
            return JSONResultUtil.success();
        }

        return JSONResultUtil.error("刪除失敗");
    }

    @GetMapping("/listAll")
    public JSONResultUtil<List<Map<String, Object>>> listAll() {
        List<Map<String, Object>> datas = getBaseService().selectMaps(null);
        return JSONResultUtil.successWithData(datas);
    }
}

PaymentController：

package cn.qz.cloud.controller;

import cn.qz.cloud.bean.Payment;
import cn.qz.cloud.service.PaymentService;
import com.baomidou.mybatisplus.service.IService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Author: qlq
 * @Description
 * @Date: 14:49 2020/9/25
 */
@RestController
@RequestMapping("/pay")
public class PaymentController extends AbstractController<Payment, Long> {

    @Autowired
    private PaymentService service;

    @Override
    public IService<Payment> getBaseService() {
        return service;
    }
}

6.啟動后用postman測試 

(1)測試創建：

返回結果：

{
  "success": true,
  "code": "200",
  "msg": "",
  "data": {
    "id": 2,
    "createtime": "2020-09-25T07:06:09.754+0000",
    "serial": "測試"
  }
}

（2）測試查詢所有：

3. 訂單模塊完成 

　　步驟同上面的支付模塊類似。使用80端口。主要使用RestTemplate調用支付模塊。

1.新建moudle

(1) 新建完成之后查看父pom.xml文件會多一個moudle。

(2)新的order模塊的pom文件只有artifactId，沒有G和A，會采用父類的G和A。

2.修改pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud</artifactId>
        <groupId>cn.qz.cloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>cloud-consumer-order80</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!-- spring-boot整合mybatis-plus -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.10</version>
        </dependency>
        <!--mysql-connector-java-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--jdbc-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <!-- springdata jpa依賴 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

3.修改application.yml

server:
  port: 80

4. 編寫啟動類

package cn.qz.cloud;

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

/**
 * 啟動類
 */
@SpringBootApplication
public class OrderConsumerMain80 {
    public static void main(String[] args) {
        SpringApplication.run(OrderConsulMain80.class, args);
    }
}

5. 業務類

(0)JSON工具類

package cn.qz.cloud.utils;

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

import java.io.Serializable;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class JSONResultUtil<T> implements Serializable {

    private static final long serialVersionUID = 3637122497350396679L;

    private boolean success;

    private String code;

    private String msg;

    private T data;

    public static <T> JSONResultUtil<T> success() {
        return new JSONResultUtil<>(true, "200", "", null);
    }

    public static <T> JSONResultUtil<T> successWithData(T data) {
        return new JSONResultUtil<>(true, "200", "", data);
    }

    public static <T> JSONResultUtil<T> error(String codeOrMsg) {
        return errorWithData(codeOrMsg, null);
    }

    public static <T> JSONResultUtil<T> errorWithMsg(String errorCode, String msg) {
        return new JSONResultUtil<T>(false, errorCode, msg, null);
    }

    public static <T> JSONResultUtil<T> errorWithData(String codeOrMsg, T data) {
        return new JSONResultUtil<T>(false, codeOrMsg, codeOrMsg, data);
    }
}

(1)bean

package cn.qz.cloud.bean;

import lombok.Getter;
import lombok.Setter;

import java.util.Date;

@Getter
@Setter
public abstract class AbstractSequenceEntity {

    private static final long serialVersionUID = -674790161451253326L;

    protected Long id;

    protected Date createtime;

    public AbstractSequenceEntity() {
        this.createtime = new Date();
    }
}

Payment：

package cn.qz.cloud.bean;

import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

/**
 * @Author: qlq
 * @Description
 * @Date: 22:37 2020/9/24
 */
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
@Getter
@Setter
public class Payment extends AbstractSequenceEntity {

    private String serial;
}

(2)配置類：注入RestTemplate

package cn.qz.cloud.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

/**
 * 注入一個bean
 */
@Configuration
public class ApplicationContextConfig {
    @Bean
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }
}

(3)Controller類

package cn.qz.cloud.controller;

import cn.qz.cloud.bean.Payment;
import cn.qz.cloud.utils.JSONResultUtil;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;
import java.util.List;
import java.util.Map;

/**
 * @Author: qlq
 * @Description
 * @Date: 22:09 2020/9/25
 */
@RestController
@RequestMapping("/consumer")
public class OrderController {

    private static final String PAYMENT_URL = "http://localhost:8081";

    @Resource
    private RestTemplate restTemplate;

    @PostMapping("/pay/save")
    public JSONResultUtil<Payment> save(@RequestBody Payment payment) {
        return restTemplate.postForObject(PAYMENT_URL + "/pay/save", payment, JSONResultUtil.class);
    }

    @GetMapping("/pay/listAll")
    public JSONResultUtil<List<Map<String, Object>>> listAll() {
        return restTemplate.getForObject(PAYMENT_URL + "/pay/listAll", JSONResultUtil.class);
    }
}

　　接下來測試即可。

4. 工程重構

　　發現上面兩個工程有許多重復的地方，因此決定抽取公共模塊。

1.新建工程

 2. 修改pom.xml

　　抽取了公共pom，增加了工具類。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud</artifactId>
        <groupId>cn.qz.cloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>cloud-api-commons</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.1.0</version>
        </dependency>
    </dependencies>

</project>

3.抽取代碼

　　主要是抽取bean和抽取utils到新工程中。

 4. 發布工程

　　執行 mvn clean install發布到本地倉庫。

5.修改支付模塊和訂單模塊的pom,加入下面配置

        <!--引入自己抽取的工具包-->
        <dependency>
            <groupId>cn.qz.cloud</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>${project.version}</version>
        </dependency>

　　測試即可。

 

補充：關於mapper層注解@Mapper、@Repository、@MapperScan的區別 

　　@Mapper 是 Mybatis 的注解，和 Spring 沒有關系， @Mapper不需要配置掃描地址，通過xml里面的namespace里面的接口地址，生成了Bean后注入到Service層中。在 Spring 程序中，Mybatis 需要找到對應的 mapper，在編譯的時候動態生成代理類，實現數據庫查詢功能，所以我們需要在接口上添加 @Mapper 注解。

　　@Repository 是 Spring 的注解，用於聲明一個 Bean，需要在Spring中配置掃描地址，然后生成Dao層的Bean才能被注入到Service層中。

　　@MapperScan是配置掃描Mapper包的配置，可以在啟動類上添加該注解，自動掃描包路徑下的所有接口，使用這種方法接口上不用添加任何注解。

　　一個Mapper接口中，其注解滿足如下規則：@Mapper 一定要有，否則 Mybatis 找不到 mapper。@Repository 可有可無，可以消去依賴注入的報錯信息。@MapperScan 可以替代 @Mapper(配置了MapperScan不需要每個Mapper接口都寫@Mapper注解)。

補充：一個IDEA熱部署的工具

 　　在settings/plugins搜索Jrebel。安裝之后以Jrebel啟動項目即可，改完某個類會熱加載。

補充：IDEA開啟RunDashboard

.idea文件夾下面workspace.xml搜索RunDashboard，之后加入：

  <option name="configurationTypes">
    <set>
      <option value="SpringBootApplicationConfigurationType" />
    </set>
  </option>

 最終的代碼如下：

  <component name="RunDashboard">
    <option name="ruleStates">
      <list>
        <RuleState>
          <option name="name" value="ConfigurationTypeDashboardGroupingRule" />
        </RuleState>
        <RuleState>
          <option name="name" value="StatusDashboardGroupingRule" />
        </RuleState>
      </list>
    </option>
    <option name="configurationTypes">
          <set>
            <option value="SpringBootApplicationConfigurationType" />
          </set>
    </option>    
  </component>

 補充：springboot項目中配置server.port = 0 的時候會自動選取一個未被占用的端口啟動項目，在一個服務器啟動多個應用的時候非常有用。也可以server.port=-1；http的端口有范圍：1～65535，-1是訪問不了的，放開-1是為了：完全關閉HTTP端點，但仍創建一個WebApplicationContext.

 補充：Maven中pom.xml中的properties中定義的版本信息也可以被子pom繼承下去