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Guice依赖注入(接口多实现)
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‎README.md

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- [Guice依赖注入(一)](guice/binder/DOC.md)
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- [Guice依赖注入(构造函数注入)](guice/binder-constructor/DOC.md)
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- [Guice依赖注入(接口多实现)](guice/binder-multiple/DOC.md)
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‎guice/README.md

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- [Guice依赖注入(一)](binder/DOC.md)
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- [Guice依赖注入(构造函数注入)](binder-constructor/DOC.md)
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- [Guice依赖注入(接口多实现)](binder-multiple/DOC.md)

‎guice/binder-multiple/DOC.md

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# Guice依赖注入(接口多实现)
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本教程主要详细讲解Guice依赖注入中的特性接口多实现，一般使用到guice的框架的插件机制都是基于该方式实现。
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#### 基础环境
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---
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| 技术 | 版本 |
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| ----- | ----- |
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| Java | 1.8+ |
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| Guice | 4.2.3 |
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#### 初始化项目
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---
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- 初始化项目
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```bash
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mvn archetype:generate -DgroupId=com.edurt.sli.guice -DartifactId=guice-binder-multiple -DarchetypeArtifactId=maven-archetype-quickstart -Dversion=1.0.0 -DinteractiveMode=false
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```
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- 修改pom.xml增加Guice依赖
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>learn-integration-guice</artifactId>
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<groupId>com.edurt.sli.guice</groupId>
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<version>1.0.0</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>guice-binder-multiple</artifactId>
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<name>Guice依赖注入(接口多实现)</name>
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<properties>
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<system.java.version>1.8</system.java.version>
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<guice.version>4.2.3</guice.version>
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<lombok.version>1.18.2</lombok.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>com.google.inject</groupId>
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<artifactId>guice</artifactId>
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<version>${guice.version}</version>
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</dependency>
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<version>${lombok.version}</version>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>${plugin.maven.compiler.version}</version>
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<configuration>
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<source>${system.java.version}</source>
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<target>${system.java.version}</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>
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```
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`guice`: guice就是我们核心要使用的依赖
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#### 接口多实现注入
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---
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如果一个接口有多个实现，如果单单通过`@Inject`和`Module`都难以直接实现，但多实现是经常会出现的，Guice提供了其它注入方式来解决此问题。
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- 创建`com.edurt.sli.guice.multiple`文件夹，并在该文件夹下创建`Service`接口文件，用于添加我们需要测试的函数
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```java
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package com.edurt.sli.guice.multiple;
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public interface Service {
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void print(String source);
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}
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```
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- 创建`Service`接口的实现类`JavaService`和`GuiceService`，用于实现接口中的方法，代码如下
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```java
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package com.edurt.sli.guice.multiple;
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public class JavaService implements Service {
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@Override
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public void print(String source) {
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System.out.println("Java Service " + source);
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}
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}
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```
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```java
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package com.edurt.sli.guice.multiple;
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public class GuiceService implements Service {
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@Override
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public void print(String source) {
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System.out.println("Guice Service " + source);
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}
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}
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```
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- 创建`Guice`和`Java`注解类，用于提供guice框架标识
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.BindingAnnotation;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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@Retention(RetentionPolicy.RUNTIME)
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@Target({ElementType.FIELD, ElementType.PARAMETER})
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@BindingAnnotation
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public @interface Guice {
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}
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```
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.BindingAnnotation;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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@Retention(RetentionPolicy.RUNTIME)
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@Target({ElementType.FIELD, ElementType.PARAMETER})
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@BindingAnnotation
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public @interface Java {
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}
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```
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- 创建用于测试注入的应用类`Application`，代码如下
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.Guice;
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import com.google.inject.Inject;
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public class Application {
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@Inject
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@Java
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public Service java;
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@Inject
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@com.edurt.sli.guice.multiple.Guice
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public Service guice;
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public static void main(String[] args) {
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Application application = Guice.createInjector(binder -> {
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binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class);
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binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class);
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}).getInstance(Application.class);
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application.guice.print("sss");
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application.java.print("sss");
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}
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}
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```
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我们运行程序输出
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```bash
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Guice Service sss
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Java Service sss
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```
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我们注意看`binder`的配置中，我们将注解与实际的实现类绑定到了一起，这样就实现了绑定多接口实现的功能。
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> 注意：在本次程序中我们使用的是lambda表达式进行的代码编程，需要jdk1.8及以上版本
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#### 静态代码注入
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---
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我们如果需要进行静态代码注入服务该怎么写呢？我们参照以前讲解的`Guice依赖注入(构造函数注入)`资源中，我们创建一个`ApplicationStatic`类进行static的注入，代码如下
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.Inject;
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public class ApplicationStatic {
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@Inject
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@Java
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public static Service java;
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@Inject
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@com.edurt.sli.guice.multiple.Guice
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public static Service guice;
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public static void main(String[] args) {
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com.google.inject.Guice.createInjector(binder -> {
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binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class);
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binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class);
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binder.requestStaticInjection(ApplicationStatic.class);
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});
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ApplicationStatic.guice.print("sss");
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ApplicationStatic.java.print("sss");
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}
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}
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```
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我们只需要在binder阶段将我们的主类注入到guice容器中，也就是我们看到的`binder.requestStaticInjection(ApplicationStatic.class);`代码，运行程序输出以下内容
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```java
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Guice Service sss
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Java Service sss
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```
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#### 属性绑定多接口
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---
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先看一下多接口绑定的示例
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.Guice;
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import com.google.inject.Inject;
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public class ApplicationMultipleProperty {
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@Inject
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public Service java;
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@Inject
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public Service guice;
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public static void main(String[] args) {
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ApplicationMultipleProperty application = Guice.createInjector(binder -> {
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binder.bind(Service.class).annotatedWith(Java.class).to(JavaService.class);
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binder.bind(Service.class).annotatedWith(com.edurt.sli.guice.multiple.Guice.class).to(GuiceService.class);
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}).getInstance(ApplicationMultipleProperty.class);
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application.guice.print("sss");
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application.java.print("sss");
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}
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}
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```
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运行以上代码，就会出现以下错误
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```java
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Exception in thread "main" com.google.inject.ConfigurationException: Guice configuration errors:
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1) No implementation for com.edurt.sli.guice.multiple.Service was bound.
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Did you mean?
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* com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Java
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* com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Guice
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while locating com.edurt.sli.guice.multiple.Service
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for field at com.edurt.sli.guice.multiple.Application.guice(Application.java:6)
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while locating com.edurt.sli.guice.multiple.Application
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2) No implementation for com.edurt.sli.guice.multiple.Service was bound.
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Did you mean?
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* com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Java
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* com.edurt.sli.guice.multiple.Service annotated with interface com.edurt.sli.guice.multiple.Guice
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while locating com.edurt.sli.guice.multiple.Service
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for field at com.edurt.sli.guice.multiple.Application.java(Application.java:6)
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while locating com.edurt.sli.guice.multiple.Application
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2 errors
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at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:1120)
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at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:1078)
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at com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1131)
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at com.edurt.sli.guice.multiple.Application.main(Application.java:18)
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```
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这是因为我们使用了属性绑定了多接口实现，导致guice无法识别具体是哪个实现类，不过guice是强大的这种问题也被考虑到了，只需要使用`@Named`模板生成注解即可解决，我们姜代码修改为以下内容
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```java
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package com.edurt.sli.guice.multiple;
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import com.google.inject.Guice;
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import com.google.inject.Inject;
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import com.google.inject.name.Named;
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import com.google.inject.name.Names;
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public class ApplicationMultipleProperty {
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@Inject
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@Named("Java")
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public Service java;
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@Inject
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@Named("Guice")
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public Service guice;
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public static void main(String[] args) {
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ApplicationMultipleProperty application = Guice.createInjector(binder -> {
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binder.bind(Service.class).annotatedWith(Names.named("Java")).to(JavaService.class);
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binder.bind(Service.class).annotatedWith(Names.named("Guice")).to(GuiceService.class);
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}).getInstance(ApplicationMultipleProperty.class);
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application.guice.print("sss");
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application.java.print("sss");
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}
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}
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```
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运行程序后，输出以下结果
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```java
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Guice Service sss
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Java Service sss
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```
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这个示例也很好理解，其实我们只是做了两步操作
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- 在绑定实现的时候使用`annotatedWith(Names.named("Java"))`进行对该服务实现做名称标志
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- 在需要使用服务实现的地方使用`@Named("Java")`进行服务的引用即可
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#### 打包文件部署
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---
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- 打包数据
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```bash
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mvn clean package -Dmaven.test.skip=true -X
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```
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运行打包后的文件即可
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```bash
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java -jar target/guice-binder-multiple-1.0.0.jar
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```
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#### 源码地址
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---
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- [GitHub](https://github.com/EdurtIO/spring-learn-integration/tree/master/guice/binder-multiple)
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- [Gitee](https://gitee.com/qianmoQ/spring-learn-integration/tree/master/guice/binder-multiple)

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