Guice

Guice is a lightweight dependency injection framework for Java 6 and above, brought to you by Google.

Users’ guide

入门教程

Quick Start

Hello World

  • jar 的引入
<!-- https://mvnrepository.com/artifact/com.google.inject/guice -->
<dependency>
    <groupId>com.google.inject</groupId>
    <artifactId>guice</artifactId>
    <version>4.1.0</version>
</dependency>
  • HelloWorld.java & implements
public interface HelloWorld {

    void hello();

}

public class HelloWorldImpl implements HelloWorld {

    @Override
    public void hello() {
        System.out.println("hello world");
    }

}
  • Test
/**
 * 简单绑定使用
 */
@Test
public void helloTest() throws Exception {
    Injector injector = Guice.createInjector(new Module() {
        @Override
        public void configure(Binder binder) {
            binder.bind(HelloWorld.class).to(HelloWorldImpl.class);
        }
    });
    HelloWorld helloWorld = injector.getInstance(HelloWorld.class);
    helloWorld.hello();
}

单例

  • 是单例吗？
/**
 * 默认创建的不是单例
 */
@Test
public void isSingletonTest() {
    Injector injector = Guice.createInjector(new Module() {
        @Override
        public void configure(Binder binder) {
            binder.bind(HelloWorld.class).to(HelloWorldImpl.class);
        }
    });
    HelloWorld helloWorld = injector.getInstance(HelloWorld.class);
    HelloWorld helloWorldTwo = injector.getInstance(HelloWorld.class);
    Assert.assertEquals(helloWorld.hashCode(), helloWorldTwo.hashCode());
}
  • 如何创建单例？
/**
 * 单例
 */
@Test
public void singletonTest() {
    Injector injector = Guice.createInjector(new Module() {
        @Override
        public void configure(Binder binder) {
            binder.bind(HelloWorld.class).to(HelloWorldImpl.class).in(Scopes.SINGLETON);
        }
    });
    HelloWorld helloWorld = injector.getInstance(HelloWorld.class);
    HelloWorld helloWorldTwo = injector.getInstance(HelloWorld.class);
    Assert.assertEquals(helloWorld.hashCode(), helloWorldTwo.hashCode());
}

Annotation

有没有觉得 Injector 代码太多，可以使用注解简化代码。

  • HelloWorldAnnotation.java & implements
@ImplementedBy(HelloWorldAnnotationImpl.class)
public interface HelloWorldAnnotation {

    void hello();

}

public class HelloWorldAnnotationImpl implements HelloWorldAnnotation {
    @Override
    public void hello() {
        System.out.println("Hello World Annotation!");
    }
}
  • Test
public class HelloWorldAnnotationImplTest {


    /**
     * 依赖于注解的实现
     * 1. 可以发现相对于 spring，guice 更加的轻量级。
     * 2. 这种写法有个缺点。让接口依赖于实现了。如果有多个实现怎么办？
     */
    @Test
    public void helloTest() throws Exception {
        Injector injector = Guice.createInjector();
        HelloWorldAnnotation annotation = injector.getInstance(HelloWorldAnnotation.class);
        annotation.hello();
    }

}