将 SSM 工程拆分为多个模块开发：
ssm_parent：将所需的依赖都配置在 pom 中。
ssm_dao：负责dao层业务。
ssm_service：负责service层业务。
ssm_web：负责web层业务。
Snipaste_2019-07-11_00-01-40.png
理解继承和聚合
通常继承和聚合同时使用。
何为继承？
继承是为了消除重复，如果将 dao、service、web 分开创建独立的工程则每个工程的 pom.xml文件中的内容存在重复，比如：设置编译版本、锁定 spring 的版本的等，可以将这些重复的配置提取出来在父工程的 pom.xml 中定义。
何为聚合？
项目开发通常是分组分模块开发，每个模块开发完成要运行整个工程需要将每个模块聚合在一起运行，比如：dao、service、web 三个工程最终会打一个独立的 war 运行。
详细代码及配置文件请参考《Spring，SpringMVC，Mybatis三大框架整合》文章，这里只是对这篇文章的相关代码的复制粘贴。
ssm_parent
pom文件：
<?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>com.gzy</groupId>
<artifactId>ssm_perent</artifactId>
<version>1.0-SNAPSHOT</version>
<!--依赖模块-->
<modules>
<module>../ssm_dao</module>
<module>../ssm_web</module>
<module>../ssm_service</module>
</modules>
<!--打包为pom包-->
<packaging>pom</packaging>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
</dependency>
</dependencies>
<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>
<!--
特别同种家族版本 使用定义 属性 下方 可以使用 ${名字}
-->
<spring.version>5.1.8.RELEASE</spring.version>
<!--
集中管理
-->
<mybatis.version>3.5.1</mybatis.version>
<mybatis.spring.version>2.0.1</mybatis.spring.version>
<aspectjweaver.version>1.9.4</aspectjweaver.version>
<mysql.version>8.0.16</mysql.version>
<jackson.version>2.9.9</jackson.version>
<hikari.version>3.3.1</hikari.version>
</properties>
<!--
依赖管理 这里面写的配置不是 不是 不是用来导包
用来锁定版本号的
-->
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jcl</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>${aspectjweaver.version}</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>${mybatis.version}</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>${mybatis.spring.version}</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql.version}</version>
</dependency>
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>${hikari.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>${jackson.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
</project>
---模块结构---
Snipaste_2019-07-10_23-59-20.png
ssm_dao
pom文件：
<?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>ssm_perent</artifactId>
<groupId>com.gzy</groupId>
<version>1.0-SNAPSHOT</version>
<relativePath>../ssm_perent/pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>ssm_dao</artifactId>
<packaging>pom</packaging>
<modules>
<module>../ssm_service</module>
</modules>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<!--只有dao层需要的依赖-->
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
</dependency>
</dependencies>
</project>
---模块结构---
Snipaste_2019-07-10_23-52-49.png
ssm_service
pom文件：
<?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>ssm_dao</artifactId>
<groupId>com.gzy</groupId>
<version>1.0-SNAPSHOT</version>
<relativePath>../ssm_perent/pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>ssm_service</artifactId>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<dependency>
<groupId>com.gzy</groupId>
<artifactId>ssm_dao</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
</dependencies>
</project>
---模块结构---
Snipaste_2019-07-10_23-55-42.png
ssm_web
pom文件：
<?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>ssm_perent</artifactId>
<groupId>com.gzy</groupId>
<version>1.0-SNAPSHOT</version>
<relativePath>../ssm_perent/pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>ssm_web</artifactId>
<packaging>war</packaging>
<name>ssm_web Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!-- JSTL stop -->
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>com.gzy</groupId>
<artifactId>ssm_service</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
</dependencies>
<build>
<finalName>ssm_web</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
---模块结构---
Snipaste_2019-07-10_23-56-59.png
注意
ssm_web的web.xml配置有所不同
Snipaste_2019-07-11_00-06-29.png
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