Java中使用Gradle中声明的变量

问题描述

是否可以在Gradle中声明一个可用于Java的变量？即在build.gradle中声明一些vars，然后在构建时得到这些变量。就像在C/C++中的pre-processor宏…

参考：https://stackoverflow.com/questions/17197636/is-it-possible-to-declare-a-variable-in-gradle-usable-in-java

最佳解决方案

生成Java常量

android {
    buildTypes {
        debug {
            buildConfigField "int", "FOO", "42"
            buildConfigField "String", "FOO_STRING", "\"foo\""
            buildConfigField "boolean", "LOG", "true"
        }

        release {
            buildConfigField "int", "FOO", "52"
            buildConfigField "String", "FOO_STRING", "\"bar\""
            buildConfigField "boolean", "LOG", "false"
        }
    }
}

可以使用BuildConfig.FOO访问

生成Android资源

android {
    buildTypes {
        debug {
            resValue "string", "app_name", "My App Name Debug"
        }
        release {
            resValue "string", "app_name", "My App Name Release"
        }
    }
}

可以使用@string/app_name或R.string.app_name以常规方式访问

次佳解决方案

Store api keys with help of gradle and the gradle.properties file (Java + XML)

• gradle.properties

AppKey="XXXX-XXXX"

• build.gradle

buildTypes {
//...
    buildTypes.each {
        it.buildConfigField 'String', 'APP_KEY_1', AppKey
        it.resValue 'string', 'APP_KEY_2', AppKey
    }
}

• Usage in java code

Log.d("UserActivity", "onCreate, APP_KEY: " + getString(R.string.APP_KEY_2));

BuildConfig.APP_KEY_1

• Usage in xml code

<data android:scheme="@string/APP_KEY_2" />

Link to an example of Api App Key usage in an Android application

Using String Constants Generated by Gradle Build Configurations

第三种解决方案

使用系统属性，在build.gradle中设置，从Java应用程序读取

在build.gradle中使用test任务，使用测试任务方法systemProperty设置在运行时传递的系统属性：

apply plugin: 'java'
group = 'example'
version = '0.0.1-SNAPSHOT'

repositories {
    mavenCentral()
}

dependencies {
    testCompile 'junit:junit:4.8.2'
    compile 'ch.qos.logback:logback-classic:1.1.2'
}

test {
    logger.info '==test=='
    systemProperty 'MY-VAR1', 'VALUE-TEST'
}

Java中获取系统属性MY-VAR1，在runtime被设置为VALUE-TEST：

package example;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HelloWorld {
    static final Logger log = LoggerFactory.getLogger(HelloWorld.class);
    public static void main(String args[]) {
        log.info("entering main...");
        final String val = System.getProperty("MY-VAR1", "UNSET (MAIN)");
        System.out.println("(main.out) hello, world: " + val);
        log.info("main.log) MY-VAR1=" + val);
    }
}