!["Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/cover.png)
## 背景
> 项目为什么需要用多模块？springmvc难道还不够我们平常使用吗？
1. 设计模式真言：“高内聚、低耦合”，springmvc项目，一般会把项目分成多个包：controller、service、dao、util等，但是随着项目的复杂性提高，想复用其他一个模块的话，因为是包的形式，剥离出来会比较困难，耦合性有点强，常用的方法就是复制代码修改，但是这样会做很多无用功与增加出错几率。
2. springboot多模块简单来说，就是把按包分模块的模式，借助maven升级到jar的方式，抽象性更加强了，假如jar再升级到到war或者多个集合jar，就成微服务了，在多模块jar模式下可以将某个jar拿出来对外共用，能大大提高代码复用率与开发效率。

## 话不多说开搞

## springboot多模块创建
### 父模块创建
- 打开idea：选择Create New Project

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/01.png "公众号:Madison龙少")

> 或者去[官网](https://start.spring.io/)创建（跟idea船舰项目是一样的，我这里用的是idea）

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/02.png "公众号:Madison龙少")
- 然后选择Spring Initializr

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/03.png "公众号:Madison龙少")

- 点击next之后—>基本设置

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/04.png "公众号:Madison龙少")

- 点击next之后->添加依赖

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/05.png "公众号:Madison龙少")

- 点击next之后->选择项目地址

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/06.png "公众号:Madison龙少")

- 点击finish之后

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/07.png "公众号:Madison龙少")

### 子模块创建
- 父项目名称->右键->new->moudle

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/08.png "公众号:Madison龙少")

- 点击Spring Initializr(选择合适jdk版本)->next

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/09.png "公众号:Madison龙少")

- 点击next之后->设置Maven Project 而不是跟父项目相同的Maven Pom

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/10.png "公众号:Madison龙少")

- 点击next之后->添加依赖

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/11.png "公众号:Madison龙少")

- 点击next->选择确认项目地址

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/12.png "公众号:Madison龙少")

- 点击finish完成

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/13.png "公众号:Madison龙少")

> 然后再创建一个子模块multi-core 过程跟multi-controller一样，我这里就省略了。我们这里就暂时创建两个子模块。

- 项目创建完成整体结构图

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/14.png "公众号:Madison龙少")

> 注：由于程序的主入口是multi-controller 所有 multi-core里面 application.properties MultiCoreApplication.java 文件都删除了

### 修改pom文件
1.修改父项目pom-修改完成如下所示（有注释）

```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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.1</version>
        <relativePath/> 
    </parent>
    <groupId>com.tinygray</groupId>
    <artifactId>multi-parent</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>multi-parent</name>
    <description>Demo project for Spring Boot</description>
    
    <packaging>pom</packaging>
    
    <modules>
        <module>multi-controller</module>
        <module>multi-core</module>
    </modules>
    
    <properties>
        <java.version>1.8</java.version>
    </properties>

<dependencies>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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>
        <dependency>
            
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-test</artifactId>
            <version>2.0.1.RELEASE</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>
```

2.修改子项目pom
- multi-controller

```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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

<artifactId>multi-controller</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>multi-controller</name>
    <description>Demo project for Spring Boot</description>
    
    <parent>
        <artifactId>multi-parent</artifactId>
        <groupId>com.tinygray</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

<dependencies>
        
        <dependency>
            <groupId>com.tinygray</groupId>
            <artifactId>multi-core</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.tinygray.multicontroller.MultiControllerApplication</mainClass>
                    <layout>JAR</layout>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>
```
- multi-core

```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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

<artifactId>multi-core</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>multi-core</name>
    <description>Demo project for Spring Boot</description>
    
    <parent>
        <artifactId>multi-parent</artifactId>
        <groupId>com.tinygray</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

</project>
```

## springboot多模块创建完成之后验证启动
### 验证
> 你如何知道你的多模块项目搭建完成并能成功启动了呢？
看下图：

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/15.png "公众号:Madison龙少")

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/16.png "公众号:Madison龙少")

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/17.png "公众号:Madison龙少")

> 出现以上图片结果就是你的多模块项目创建完成了并可以启动了

### 启动
- 找到启动类

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/18.png "公众号:Madison龙少")

- 执行启动类

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/19.png "公众号:Madison龙少")

- 执行成功

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/20.png "公众号:Madison龙少")

- 浏览器打开`http://localhost:8080`

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/21.png "公众号:Madison龙少")

- 出现以上结果表示多模块项目已经搭建完成了
### 写一个测试接口访问
- 创建两个java文件(一个实体类User一个UserController)

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/22.png "公众号:Madison龙少")
- User.java、UserController.java文件内容-很简单一个测试接

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/23.png "公众号:Madison龙少")

- 浏览器输入http://localhost:8080/user/getUserInfo

![alt "公众号:Madison龙少"](https://gitee.com/LongGroup/tinygray_picturebed/raw/master/wechat/article/springboot-multi/24.png "公众号:Madison龙少")

- 出现以上结果就表示测试成功了。
## 结束语
感谢阅读小生文章。祝大家`早日富可敌国，实现财富自由` 
 `记得点赞、评论、收藏呦~~~`

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