关于java:Guice依赖注入接口多实现

本教程次要具体解说 Guice 依赖注入中的个性接口多实现，个别应用到 guice 的框架的插件机制都是基于该形式实现。

根底环境

初始化我的项目

• 初始化我的项目

mvn archetype:generate -DgroupId=com.edurt.sli.guice -DartifactId=guice-binder-multiple -DarchetypeArtifactId=maven-archetype-quickstart -Dversion=1.0.0 -DinteractiveMode=false

• 批改 pom.xml 减少 Guice 依赖

<?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">
 <parent> <artifactId>learn-integration-guice</artifactId> <groupId>com.edurt.sli.guice</groupId> <version>1.0.0</version> </parent>
 <modelVersion>4.0.0</modelVersion>
 <artifactId>guice-binder-multiple</artifactId> <name>Guice 依赖注入(接口多实现)</name>
 <properties> <system.java.version>1.8</system.java.version> <guice.version>4.2.3</guice.version> <lombok.version>1.18.2</lombok.version> </properties>
 <dependencies> <dependency> <groupId>com.google.inject</groupId> <artifactId>guice</artifactId> <version>${guice.version}</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>${lombok.version}</version> </dependency> </dependencies>
 <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>${plugin.maven.compiler.version}</version> <configuration> <source>${system.java.version}</source> <target>${system.java.version}</target> </configuration> </plugin> </plugins> </build>
</project>

guice: guice 就是咱们外围要应用的依赖

接口多实现注入

如果一个接口有多个实现，如果单单通过 @Inject 和Module都难以间接实现，但多实现是常常会呈现的，Guice 提供了其它注入形式来解决此问题。

• 创立 com.edurt.sli.guice.multiple 文件夹，并在该文件夹下创立 Service 接口文件，用于增加咱们须要测试的函数

package com.edurt.sli.guice.multiple;
public interface Service {void print(String source);
}

• 创立 Service 接口的实现类 JavaService 和GuiceService，用于实现接口中的办法，代码如下

package com.edurt.sli.guice.multiple;
public class JavaService implements Service {
     @Override
 public void print(String source) {System.out.println("Java Service" + source); }  }

package com.edurt.sli.guice.multiple;
public class GuiceService implements Service {
     @Override
 public void print(String source) {System.out.println("Guice Service" + source); }  }

• 创立 Guice 和Java注解类，用于提供 guice 框架标识

package com.edurt.sli.guice.multiple;
import com.google.inject.BindingAnnotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.PARAMETER})
@BindingAnnotation
public @interface Guice {}

package com.edurt.sli.guice.multiple;
import com.google.inject.BindingAnnotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.PARAMETER})
@BindingAnnotation
public @interface Java {}

• 创立用于测试注入的利用类Application，代码如下

package com.edurt.sli.guice.multiple;
import com.google.inject.Guice;
import com.google.inject.Inject;
public class Application {
 @Inject @Java public Service java;
 @Inject @com.edurt.sli.guice.multiple.Guice public Service guice;
 public static void main(String[] args) {Application application = Guice.createInjector(binder -> { binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class); binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class); }).getInstance(Application.class); application.guice.print("sss"); application.java.print("sss"); }
}

咱们运行程序输入

Guice Service sss
Java Service sss

咱们留神看 binder 的配置中，咱们将注解与理论的实现类绑定到了一起，这样就实现了绑定多接口实现的性能。

留神：在本次程序中咱们应用的是 lambda 表达式进行的代码编程，须要 jdk1.8 及以上版本

动态代码注入

咱们如果须要进行动态代码注入服务该怎么写呢？咱们参照以前解说的 Guice 依赖注入(构造函数注入) 资源中，咱们创立一个 ApplicationStatic 类进行 static 的注入，代码如下

package com.edurt.sli.guice.multiple;
import com.google.inject.Inject;
public class ApplicationStatic {
 @Inject @Java public static Service java;
 @Inject @com.edurt.sli.guice.multiple.Guice public static Service guice;
 public static void main(String[] args) {com.google.inject.Guice.createInjector(binder -> { binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class); binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class); binder.requestStaticInjection(ApplicationStatic.class); }); ApplicationStatic.guice.print("sss"); ApplicationStatic.java.print("sss"); }
}

咱们只须要在 binder 阶段将咱们的主类注入到 guice 容器中，也就是咱们看到的 binder.requestStaticInjection(ApplicationStatic.class); 代码，运行程序输入以下内容

Guice Service sss
Java Service sss

属性绑定多接口

先看一下多接口绑定的示例

package com.edurt.sli.guice.multiple;
import com.google.inject.Guice;
import com.google.inject.Inject;
public class ApplicationMultipleProperty {
 @Inject public Service java;
 @Inject public Service guice;
 public static void main(String[] args) {ApplicationMultipleProperty application = Guice.createInjector(binder -> { binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class); binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class); }).getInstance(ApplicationMultipleProperty.class); application.guice.print("sss"); application.java.print("sss"); }
}

运行以上代码，就会呈现以下谬误

Exception in thread "main" com.google.inject.ConfigurationException: Guice configuration errors:
1) No implementation for com.edurt.sli.guice.multiple.Service was bound.
 Did you mean? * com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Java * com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Guice while locating com.edurt.sli.guice.multiple.Service for field at com.edurt.sli.guice.multiple.Application.guice(Application.java:6) while locating com.edurt.sli.guice.multiple.Application
2) No implementation for com.edurt.sli.guice.multiple.Service was bound.
 Did you mean? * com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Java * com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Guice while locating com.edurt.sli.guice.multiple.Service for field at com.edurt.sli.guice.multiple.Application.java(Application.java:6) while locating com.edurt.sli.guice.multiple.Application
2 errors
 at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:1120) at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:1078) at com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1131) at com.edurt.sli.guice.multiple.Application.main(Application.java:18)

这是因为咱们应用了属性绑定了多接口实现，导致 guice 无奈辨认具体是哪个实现类，不过 guice 是弱小的这种问题也被思考到了，只须要应用 @Named 模板生成注解即可解决，咱们姜代码批改为以下内容

package com.edurt.sli.guice.multiple;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.name.Named;
import com.google.inject.name.Names;
public class ApplicationMultipleProperty {@Inject @Named("Java") public Service java;
 @Inject @Named("Guice") public Service guice;
 public static void main(String[] args) {ApplicationMultipleProperty application = Guice.createInjector(binder -> { binder.bind(Service.class).annotatedWith(Names.named("Java")).to(JavaService.class); binder.bind(Service.class).annotatedWith(Names.named("Guice")).to(GuiceService.class); }).getInstance(ApplicationMultipleProperty.class); application.guice.print("sss"); application.java.print("sss"); }
}

运行程序后，输入以下后果

Guice Service sss
Java Service sss

这个示例也很好了解，其实咱们只是做了两步操作

• 在绑定实现的时候应用 annotatedWith(Names.named("Java")) 进行对该服务实现做名称标记
• 在须要应用服务实现的中央应用 @Named("Java") 进行服务的援用即可

打包文件部署

• 打包数据

mvn clean package -Dmaven.test.skip=true -X

运行打包后的文件即可

java -jar target/guice-binder-multiple-1.0.0.jar

源码地址

• GitHub
• Gitee