从零开始Java多项目构建

gradle支持多项目构建。本章将从零开始讲多项目构建。

1、多项目结构

~/Desktop/multiproject$ gradle projects

> Task :projects

------------------------------------------------------------
Root project
------------------------------------------------------------

Root project 'multiproject'
+--- Project ':api'
+--- Project ':services'
|    +--- Project ':services:shared'
|    \--- Project ':services:webservice'
\--- Project ':shared'

• 项目api编译出一个Jar文件供项目webservice使用；
• 项目shared编译出一个Jar文件存放项目api和services/webservice、项目services/shared/的共用代码；
• 项目webservice是一个返回XML文件的webapp。

2、根目录的settings.gradle

构建一个多项目，需要在根目录下创建一个settings.gradle文件，并指定哪些项目需要构建。 如：

include "shared","api","services:webservice","services:shared"

3、根目录的build.gradle

// 配置所有子项目的公共部分
subprojects {
    // 使用Java插件
    apply plugin: 'java'
    // 使用eclipse-wtp插件
    apply plugin: 'eclipse-wtp'

    // 外部依赖的仓库，到时gradle在本地找不到就可以到仓库找依赖
    repositories {
       mavenCentral()
    }

    // 外部依赖
    dependencies {
        testCompile 'junit:junit:4.12'
    }
    // 指定项目版本号
    version = '1.0'
    // 指定JDK版本号
    sourceCompatibility = '1.8'
    jar {
        manifest.attributes provider: 'gradle'
    }
}

allprojects {

    tasks.create('hello') {
        doLast {
            task ->
                print "project name is $task.project.name \n"
        }
    }
 }

• subprojects{}：配置这个项目的子项目。使用多模块项目时，不同模块之间有相同的配置，导致重复配置，可以将相同的部分抽取出来，使用配置注入的技术完成子项目的配置。根项目就像一个容器, subprojects 方法遍历这个容器的所有元素并且注入指定的配置。allprojects是对所有project的配置，包括Root Project。而subprojects是对所有Child Project的配置
• buildscript{}里是gradle脚本执行所需依赖，分别是对应的maven库和插件。
• allprojects里是项目本身需要的依赖，比如代码中某个类是打包到maven私有库中的，那么在allprojects->repositories中需要配置maven私有库，而不是buildscript中，不然找不到

4、Gradle Java插件的约定

参考《使用gradle构建Java项目》 Gradle Java插件有以下约定：

1. 存放项目源码：src/main/java
2. 存放测试源码：src/test/java
3. 存放资源文件：src/main/resources
4. 在src/test/resources目录下的任何文件都会被添加到classpath中用于运行测试
5. 所有的输出文件都被创建在build目录里，其中JAR文件在build/libs目录里

3、根据约定创建目录

/*api 项目*/
~/Desktop/multiproject$ mkdir api
~/Desktop/multiproject$ mkdir -p api/src/main/java
~/Desktop/multiproject$ mkdir -p api/src/main/resources
~/Desktop/multiproject$ mkdir -p api/src/test/java
~/Desktop/multiproject$ mkdir -p api/src/test/resources
/*api建两个包*/
/*com.wong.api*/
~/Desktop/multiproject$ mkdir -p api/src/main/java/com/wong/api
/*com.wong.api.impl*/
~/Desktop/multiproject$ mkdir -p api/src/main/java/com/wong/api/impl


/*shared项目*/
~/Desktop/multiproject$ mkdir shared
~/Desktop/multiproject$ mkdir -p shared/src/main/java
~/Desktop/multiproject$ mkdir -p shared/src/main/resources
~/Desktop/multiproject$ mkdir -p shared/src/test/java
~/Desktop/multiproject$ mkdir -p shared/src/test/resources
/*创建包*/
/*com.wong.shared*/
~/Desktop/multiproject$ mkdir -p shared/src/main/java/com/wong/shared
/*com.wong.shared*/
~/Desktop/multiproject$ mkdir -p shared/src/test/java/com/wong/shared
/*resources*/
~/Desktop/multiproject$ mkdir -p shared/src/main/resources/com/wong/shared
~/Desktop/multiproject$ mkdir -p shared/src/test/resources/com/wong/shared

/*services/shared项目*/
~/Desktop/multiproject$ mkdir -p services/shared
~/Desktop/multiproject$ mkdir -p services/shared/src/main/java
~/Desktop/multiproject$ mkdir -p services/shared/src/main/resources
~/Desktop/multiproject$ mkdir -p services/shared/src/test/java
~/Desktop/multiproject$ mkdir -p services/shared/src/test/resources
/*创建包com.wong.services.shared*/
~/Desktop/multiproject$ mkdir -p services/shared/src/main/java/com/wong/services/shared

/*services/webservice项目*/
~/Desktop/multiproject$ mkdir -p services/webservice
~/Desktop/multiproject$ mkdir -p services/webservice/src/main/java
~/Desktop/multiproject$ mkdir -p services/webservice/src/main/resources
~/Desktop/multiproject$ mkdir -p services/webservice/src/test/java
~/Desktop/multiproject$ mkdir -p services/webservice/src/test/resources
/*创建两个包*/
/*com.wong.webservice*/
~/Desktop/multiproject$ mkdir -p services/webservice/src/main/java/com/wong/webservice
/*com.wong.webservice*/
~/Desktop/multiproject$ mkdir -p services/webservice/src/test/java/com/wong/webservice

4、向各个目录加入源码文件

（一）项目api

• 添加PersonList.java

~/Desktop/multiproject$ touch api/src/main/java/com/wong/api/PersonList.java
~/Desktop/multiproject$ vim api/src/main/java/com/wong/api/PersonList.java

package com.wong.api;

import java.util.ArrayList;
import com.wong.shared.Person;
import com.wong.api.impl.Impl;

public class PersonList{
        private ArrayList<Person> persons = new ArrayList<Person>();
        
        public void doWithImpl(){
                try{
                        Class.forName("org.apache.commons.io.FileUtils");
                }catch(ClassNotFoundException e){
                        throw new RuntimeException(e);
                }       
                new Impl().implMethod();
        }       
}

• Impl.java

package com.wong.api.impl;

public class Impl{
        public void implMethod(){
                double a = 4.0 * 4;
        }       
}

• 添加构建脚本build.gradle

~/Desktop/multiproject$ touch api/build.gradle
~/Desktop/multiproject$ vim build.gradle

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'commons-math:commons-math:1.1'
    }
}

configurations {
   spi
}

dependencies {
    compile project(':shared')
    compile module("commons-lang:commons-lang:2.4") {
        dependency("commons-io:commons-io:1.2")
    }
}

// Just a smoke test that using this option does not lead to any exception
compileJava.options.compilerArgs = ['-Xlint:unchecked']

task spiJar(type: Jar) {
    appendix = 'spi'
    from sourceSets.main.output
    include 'com/wong/api/'
}

artifacts {
  spi spiJar
}

task dist(type: Zip) {
    dependsOn spiJar
    from 'src/dist'
    into('libs') {
        from spiJar.archivePath
        from configurations.runtime
    }
}

artifacts {
   archives dist
}

// We want to test if commons-math was properly added to the build script classpath
org.apache.commons.math.fraction.Fraction lhs = new org.apache.commons.math.fraction.Fraction(1, 3);
org.gradle.buildsrc.BuildSrcClass bsc = new org.gradle.buildsrc.BuildSrcClass()

task checkProjectDependency(dependsOn: project(':shared').jar) {
    doLast {
        File cachedSharedJarDir = new File(gradle.gradleUserHomeDir, "cache/multiproject/shared/jars")
        copy {
            from project(':shared').jar.archivePath
            into cachedSharedJarDir
        }
        File sharedJar = configurations.compile.files.find { File file -> file.name.startsWith('shared') }
        assert sharedJar.absolutePath == project(':shared').jar.archivePath.absolutePath
    }
}

（二）项目shared

• 添加资源文件main.properties

~/Desktop/multiproject$ touch shared/src/main/resources/com/wong/shared/main.properties
~/Desktop/multiproject$ vim shared/src/main/resources/com/wong/shared/main.properties

并加入如下内容：

main=mainValue

• 添加Person.java

~/Desktop/multiproject$ touch shared/src/main/java/com/wong/shared/Person.java
~/Desktop/multiproject$ vim shared/src/main/java/com/wong/shared/Person.java

package com.wong.shared;

import java.util.Properties;
import java.io.IOException;

public class Person{
        private String name;
        public Person(String name){
                this.name = name;
        }
        public String getName(){
                return name;
        }
        public void setName(String name){
                this.name = name;
        }

        public String readProperty() throws IOException{
                Properties properties = new Properties();
                properties.load(getClass().getClassLoader().getResourceAsStream("com/wong/shared/main.properties"));
                return properties.getProperty("main");
        }
}

（三）项目services/shared

• 添加TestPerson.java

~/Desktop/multiproject$ touch services/shared/src/main/java/com/wong/services/shared/TestPerson.java
~/Desktop/multiproject$ vim services/shared/src/main/java/com/wong/services/shared/TestPerson.java

package com.wong.services.shared;

import com.wong.shared.Person;

public class TestPerson{
        private String name;
        public void method(){
                new Person("Tom");
        }       
}

因为上面要用到项目shared里的Person类，所以我们要为项目services/shared，添加依赖，因此在services/shared根目录下创建build.gradle，并添加如下内容：

~/Desktop/multiproject$ touch services/shared/build.gradle
~/Desktop/multiproject$ vim services/shared/build.gradle

dependencies{
        implementation project(':shared')
}

（四）项目services/webservice

• 添加TestMan.java

~/Desktop/multiproject$ touch services/webservice/src/main/java/com/wong/webservice/TestMan.java
~/Desktop/multiproject$ vim services/webservice/src/main/java/com/wong/webservice/TestMan.java

package com.wong.webservice;

import org.apache.commons.io.FilenameUtils;
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.collections.list.GrowthList;
import com.wong.shared.Person;
import com.wong.api.PersonList;

public class TestMan{
        private String name;
        public void method(){
                FilenameUtils.separatorsToUnix("my/unix/filename");
                ToStringBuilder.reflectionToString(new Person("name"));
                new GrowthList();
                new PersonList().doWithImpl();
        }       
}

• 添加测试类TestMe

~/Desktop/multiproject$ touch services/webservice/src/test/java/com/wong/webservice/TestMe.java
~/Desktop/multiproject$ vim services/webservice/src/test/java/com/wong/webservice/TestMe.java

package com.wong.webservice;

import junit.framework.TestCase;

public class TestMe extends TestCase{
        public void testClassPath(){
                new TestPerson().method();
        }       
        
        public void testApiCompileClasspath(){
                new com.wong.api.PersonList();
        }       
}

• 为项目services/webservice添加依赖
  在services/webservice根目录下创建build.gradle，并添加如下内容：

~/Desktop/multiproject$ touch services/webservice/build.gradle
~/Desktop/multiproject$ vim services/webservice/build.gradle

apply plugin: 'war'

version = '3.0'

dependencies {
        implementation project(':shared'),'commons-collections:commons-collectio
ns:3.2.2@jar','commons-io:commons-io:1.2','commons-lang:commons-lang:2.4@jar'
        implementation project(':api',configuration:'spi')
        runtime project(':api')
}

构建结构

在根目录执行gradle build就可以编译成功了。这样多项目编译就完成了。gradle都是通过相应的插件提供的功能来完成编译的。

谢谢阅读。