是否可以在Gradle中声明一个可用于Java的变量？

程序员文章站 2022-05-26 13:58:56

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本文翻译自：Is it possible to declare a variable in Gradle usable in Java?

Is it possible to declare a variable in Gradle usable in Java ? 是否可以在Gradle中声明一个可用于Java的变量？ Basically I would like to declare some vars in the build.gradle and then getting it (obviously) at build time. 基本上我想在build.gradle中声明一些变量，然后在构建时获取它（显然）。 Just like a pre-processor macros in C/C++... 就像C / C ++中的预处理器宏一样......

An example of declaration would be something like that ... : 宣言的一个例子就是那样......：

android {
    debug {
        A_VAR_RETRIEVABLE_IN_JAVA = 42
    }
    release {
        A_VAR_RETRIEVABLE_IN_JAVA = 42+52
    }
}

Is there a way to do something like that ? 有没有办法做那样的事情？

#1楼

参考：https://stackoom.com/question/1A9tE/是否可以在Gradle中声明一个可用于Java的变量

#2楼

Generate Java Constants 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"
        }
    }
}

You can access them with BuildConfig.FOO 您可以使用BuildConfig.FOO访问它们

Generate Android resources 生成Android资源

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

You can access them in the usual way with @string/app_name or R.string.app_name 您可以使用@string/app_name或R.string.app_name以常规方式访问它们

#3楼

Example using system properties, set in build.gradle, read from Java application (following up from question in comments): 使用系统属性的示例，在build.gradle中设置，从Java应用程序中读取（从注释中的问题跟进）：

Basically, using the test task in build.gradle , with test task method systemProperty setting a system property that's passed at runtime: 基本上，使用build.gradle的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()
    // mavenLocal()
    // maven { url 'http://localhost/nexus/content/groups/public'; }
}

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'
}

And here's the rest of the sample code (which you could probably infer, but is included here anyway): it gets a system property MY-VAR1 , expected at run-time to be set to VALUE-TEST : 以下是示例代码的其余部分（您可以推断，但无论如何都包含在此处）：它获得系统属性MY-VAR1 ，在运行时期望设置为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);
  }
}

Testcase: if MY-VAR is unset, the test should fail: 测试用例：如果未设置MY-VAR ，测试应该失败：

package example;
...
public class HelloWorldTest {
    static final Logger log=LoggerFactory.getLogger(HelloWorldTest.class);
    @Test public void testEnv() {
        HelloWorld.main(new String[]{});
        final String val = System.getProperty("MY-VAR1", "UNSET (TEST)");
        System.out.println("(test.out) var1=" + val);
        log.info("(test.log) MY-VAR1=" + val);
        assertEquals("env MY-VAR1 set.", "VALUE-TEST", val);
    }
}

Run (note: test is passing): 运行（注意：测试正在通过）：

$ gradle cleanTest test
:cleanTest
:compileJava UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:compileTestJava UP-TO-DATE
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test

BUILD SUCCESSFUL

I've found that the tricky part is actually getting the output from gradle... So, logging is configured here (slf4j+logback), and the log file shows the results (alternatively, run gradle --info cleanTest test ; there are also properties that get stdout to the console, but, you know, why): 我发现棘手的部分实际上是从gradle获取输出...所以，这里配置日志（slf4j + logback），日志文件显示结果（或者，运行gradle --info cleanTest test ;有还有stdout到控制台的属性，但是，你知道，为什么）：

$ cat app.log
INFO Test worker example.HelloWorld - entering main...
INFO Test worker example.HelloWorld - main.log) MY-VAR1=VALUE-TEST
INFO Test worker example.HelloWorldTest - (test.log) MY-VAR1=VALUE-TEST

If you comment out " systemProperty... " (which, btw, only works in a test task), then: 如果您注释掉“ systemProperty... ”（其中，顺便说一下，只能在test任务中使用），那么：

example.HelloWorldTest > testEnv FAILED
    org.junit.ComparisonFailure at HelloWorldTest.java:14

For completeness, here is the logback config ( src/test/resources/logback-test.xml ): 为完整起见，这里是logback配置（ src/test/resources/logback-test.xml ）：

<configuration>
    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>app.log</file>
        <layout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%d %p %t %c - %m%n</pattern>
        </layout>
 </appender>
 <root level="info">
     <appender-ref ref="FILE"/>
</root>
</configuration>

Files: 文件：

build.gradle
src/main/java/example/HelloWorld.java
src/test/java/example/HelloWorldTest.java
src/test/resources/logback-test.xml

#4楼

An example of usage an Api App Key in an Android application (Java and XML) 在Android应用程序中使用Api App Key的示例（Java和XML）

gradle.properties gradle.properties

AppKey="XXXX-XXXX"

build.gradle 的build.gradle

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

Usage in java code 在java代码中的用法

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

BuildConfig.APP_KEY_1

Usage in xml code 在xml代码中的用法

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

#5楼

You can create build config field overridable via system environment variables during build: 您可以在构建期间通过系统环境变量创建可覆盖的构建配置字段：

Fallback is used while developing, but you can override the variable when you run the build on Jenkins or another tool. 在开发时使用Fallback，但是当您在Jenkins或其他工具上运行构建时，可以覆盖变量。

In your app build.gradle : 在您的app build.gradle中 ：

buildTypes {
        def serverUrl =  '\"' + (System.getenv("SERVER_URL")?: "http://default.fallback.url.com")+'\"'
        debug{
            buildConfigField "String", "SERVER_URL", serverUrl
        }
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            buildConfigField "String", "SERVER_URL", serverUrl
        }
    }

The variable will be available as BuildConfig.SERVER_URL . 该变量将作为BuildConfig.SERVER_URL 。

#6楼

rciovati's answer is entirely correct I just wanted to add one more tidbit that you can also create variables for every build type within the default config portion of your build.gradle. rciovati的答案是完全正确的我只是想再添加一个小工具，你也可以为build.gradle的默认配置部分中的每个构建类型创建变量。 This would look like this: 这看起来像这样：

android {
    defaultConfig {
        buildConfigField "String", "APP_NAME", "\"APP_NAME\""
    }
}

This will allow you to have access to through 这将允许您访问通过

BuildConfig.App_NAME

Just wanted to make a note of this scenario as well if you want a common config. 如果你想要一个通用的配置，也只是想记下这个场景。

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是否可以在Gradle中声明一个可用于Java的变量？

#1楼

#2楼

Generate Java Constants 生成Java常量

Generate Android resources 生成Android资源

#3楼

#4楼

An example of usage an Api App Key in an Android application (Java and XML) 在Android应用程序中使用Api App Key的示例（Java和XML）

#5楼

#6楼

在C++中，可以用于变量和函数上的关键字是哪一个？

是否可以在Gradle中声明一个可用于Java的变量？

在C++中，可以用于变量和函数上的关键字是哪一个？