使用google autoservice 自动生成java spi 描述文件

spi 是一种服务发现的标准，对于开发中我们通常需要编写 META-INF/services 文件夹中定义的类。
google auto 中的autoservice 可以帮助我们生成对应的配置，很方便

环境准备

• 项目结构

├── pom.xml

└── src

    ├── main

    │ ├── java

    │ │ └── com

    │ │ └── dalong

    │ │ ├── spi

    │ │ │ └── TranslationService.java

    │ │ └── spimpl

    │ │ ├── BingTranslationServiceProvider.java

    │ │ └── GoogleTranslationServiceProvider.java

    │ └── resources

    └── test

        └── java

            └── com

                └── dalong

                    └── SPITestClass.java

• 代码说明
  约定：
  spi中的TranslationService.java 为接口定义
  BingTranslationServiceProvider.java 以及GoogleTranslationServiceProvider.java 为接口的实现
  pom.xml 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>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <encoding>UTF-8</encoding>

        <java.version>1.8</java.version>

        <maven.compiler.source>1.8</maven.compiler.source>

        <maven.compiler.target>1.8</maven.compiler.target>

        <auto-service.version>1.0-rc6</auto-service.version>

    </properties>

    <groupId>com.dalong.appdemo</groupId>

    <artifactId>first</artifactId>

    <version>1.0-SNAPSHOT</version>

?

<dependencies>

    <dependency>

        <groupId>com.google.auto.service</groupId>

        <artifactId>auto-service-annotations</artifactId>

        <version>${auto-service.version}</version>

        <optional>true</optional>

        <scope>compile</scope>

    </dependency>

        <dependency>

            <groupId>com.google.auto.service</groupId>

            <artifactId>auto-service</artifactId>

            <version>${auto-service.version}</version>

            <optional>true</optional>

            <scope>compile</scope>

        </dependency>

    <dependency>

        <groupId>junit</groupId>

        <artifactId>junit</artifactId>

        <version>4.8</version>

        <scope>test</scope>

    </dependency>

?

</dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-site-plugin</artifactId>

                <version>3.7</version>

                <dependencies>

                    <dependency>

                        <groupId>org.apache.maven.doxia</groupId>

                        <artifactId>doxia-site-renderer</artifactId>

                        <version>1.8</version>

                    </dependency>

                </dependencies>

            </plugin>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.8.1</version>

                <configuration>

                    <annotationProcessorPaths>

                        <path>

                            <groupId>com.google.auto.service</groupId>

                            <artifactId>auto-service</artifactId>

                            <version>${auto-service.version}</version>

                        </path>

                    </annotationProcessorPaths>

                </configuration>

            </plugin>

        </plugins>

    </build>

</project>

接口定义：
TranslationService.java

package com.dalong.spi;

?

import java.util.Locale;

?

public interface TranslationService {

    String translate(String message, Locale from, Locale to);

}

实现：
BingTranslationServiceProvider.java 以及GoogleTranslationServiceProvider.java

package com.dalong.spimpl;

?

import com.dalong.spi.TranslationService;

import com.google.auto.service.AutoService;

?

import java.util.Locale;

@AutoService(TranslationService.class)

public class BingTranslationServiceProvider implements TranslationService {

    @Override

    public String translate(String message, Locale from, Locale to) {

        return "bing";

    }

}

?package com.dalong.spimpl;

?

import com.dalong.spi.TranslationService;

import com.google.auto.service.AutoService;

?

import java.util.Locale;

@AutoService(TranslationService.class)

public class GoogleTranslationServiceProvider implements TranslationService {

    @Override

    public String translate(String message, Locale from, Locale to) {

        return "google";

    }

}

?

打包构建

mvn  clean  package

效果

测试

• 代码

package com.dalong;

?

import com.dalong.spi.TranslationService;

import com.sun.prism.shader.AlphaOne_Color_AlphaTest_Loader;

import org.junit.Test;

?

import java.util.Locale;

import java.util.ServiceLoader;

import java.util.function.Consumer;

import java.util.stream.StreamSupport;

?

import static org.junit.Assert.assertEquals;

?

public class SPITestClass {

    @Test

    public void myTestForSPI(){

        ServiceLoader<TranslationService> loader = ServiceLoader.load(TranslationService.class);

        long count = StreamSupport.stream(loader.spliterator(), false).count();

?

        loader.forEach(new Consumer<TranslationService>() {

            @Override

            public void accept(TranslationService translationService) {

                Locale localeFrom = new Locale("en");

                Locale localeFo = new Locale("zh");

                String message = translationService.translate("app", localeFrom,localeFo);

                System.out.println(message);

            }

        });

        assertEquals(2, count);

    }

}

说明

基于spi 我们可以开发比较灵活的模块系统，同时可以方便的进行模块的插拔处理

参考资料

https://github.com/google/auto/tree/master/service
https://www.jianshu.com/p/46b42f7f593c

原文地址：https://www.cnblogs.com/rongfengliang/p/11695684.html