maven 多工程搭建演示

maven出现后，很多公司会用maven来构建项目，单仅仅只是单项目单工程的

并没有使用多工程来构建，这样在以后，项目越来越大，业务越来越多以后，项目会难以维护，越发庞大，维护成本提高，团队士气也会下降

等等情况，使用maven构建多工程就是如今的趋势

这边演示一个maven工程相互依赖的例子，高手轻拍，大家互相学习，有不足之处请指出

1.新建demo-parent项目，作为父工程

选择quickstart

修改pom中的jar改为pom，这样的意思是当前工程为父工程，可以再其下创建子工程

2.新建demo-project-web，作为web工程，这个工程是总的web工程，下面将会包含另外2个子web工程

选择webapp作为web工程

3.同理创建demo-project-customer-web作为子web工程（webapp），这个工程是一个独立web工程，他包含了service，dao

4.同理创建demo-project-gods-web作为子web工程（webapp），这个工程将有一个demo-project-gods-core作为后台（core就是包含了service，dao）

5.创建demo-project-gods-core作为子工程（quickstart），依赖demo-project-gods-web

6.创建demo-common，作为子工程（quickstart），作用是工具包，可被其他工程依赖引用

3-6步骤略，生成项目如下图：

父工程pom会成这样：

<modules>
      <module>demo-project-web</module>
      <module>demo-project-gods-web</module>
      <module>demo-project-customer-web</module>
      <module>demo-project-gods-core</module>
      <module>demo-common</module>
  </modules>

好，那么现在来做工程之间的依赖

首先，demo-project-web作为顶级web项目，所有的子web项目打包后都会整合在此（如果同名文件则被顶级覆盖，如果顶级没有同名文件，但是子web有同名文件，则按照依赖顺序被优先依赖的同名文件覆盖）

pom如下：

<?xml version="1.0"?>
<project
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.demo</groupId>
        <artifactId>demo-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <groupId>com.demo</groupId>
    <artifactId>demo-project-web</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>demo-project-web Maven Webapp</name>
    <url>http://maven.apache.org</url>

    <dependencies>

        <!-- 增加要合并的war包依赖 -->
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-project-gods-web</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <type>war</type>
        </dependency>
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-project-customer-web</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <type>war</type>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>

        <finalName>demo-project-web</finalName>

        <plugins>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.6</version>
                <configuration>
                    <!-- 把另外2个web子工程加入进来, 合并war -->
                    <overlays>
                        <overlay>
                            <groupId>com.demo</groupId>
                            <artifactId>demo-project-gods-web</artifactId>
                        </overlay>
                        <overlay>
                            <groupId>com.demo</groupId>
                            <artifactId>demo-project-customer-web</artifactId>
                        </overlay>
                    </overlays>
                </configuration>
            </plugin>

        </plugins>
    </build>

</project>

修改demo-project-gods-web的pom，添加自身依赖core作为service以及DAO

<?xml version="1.0"?>
<project
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.demo</groupId>
        <artifactId>demo-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <groupId>com.demo</groupId>
    <artifactId>demo-project-gods-web</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>demo-project-gods-web Maven Webapp</name>
    <url>http://maven.apache.org</url>

    <dependencies>

        <!-- 引入依赖, core中包含service以及DAO -->
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-project-gods-core</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <finalName>demo-project-gods-web</finalName>
    </build>
</project>

在customer中添加工具类依赖

<?xml version="1.0"?>
<project
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.demo</groupId>
        <artifactId>demo-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <groupId>com.demo</groupId>
    <artifactId>demo-project-customer-web</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>demo-project-customer-web Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>

        <!-- 添加common工具类依赖 -->
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-common</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

    </dependencies>
    <build>
        <finalName>demo-project-customer-web</finalName>
    </build>
</project>

============进入代码阶段============

parent是父工程，不需要编写代码

demo-common：

package org.demo.common;

import java.util.Date;

public class DateUtil {

    public static void showTime(String name) {
        System.out.println("Run in demo-common - Hello ~ " + name + ", it is " + new Date().toString());
    }
    
}

demo-project-customer-web：

package com.demo.project.customer.web;

import org.demo.common.DateUtil;

public class AbcService {

    public static void getDateService(String name) {
        DateUtil.showTime(name);
        System.out.println("Run in demo-project-customer-web...");
    }
    
}

customer.jsp

<?xml version="1.0" encoding="UTF-8" ?>
<%@page import="com.demo.project.customer.web.AbcService"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Insert title here</title>
</head>
<body>
    <%
        System.out.print("hello demo-project-customer-web customer.jsp");
        AbcService.getDateService("abc");
    %>
    
</body>
</html>

demo-project-gods-core：

package org.demo.project.gods.core;


public class Gods {

    public static void getDateService(String name) {
        System.out.println("Run in demo-project-gods-core...");
    }
    
}

demo-project-gods-web

index.jsp

<?xml version="1.0" encoding="UTF-8" ?>
<%@page import="org.demo.project.gods.core.Gods"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Insert title here</title>
</head>
<body>
    
    <%
        System.out.print("hello demo-project-gods-web gods.jsp");
        Gods.getDateService("nathan");
        
    %>
</body>
</html>

run - mvn install:

运行成功，进入相应的页面则成功