引導 ApplicationContext

Java 配置

配置類只需要是應用程式類路徑上的類，對應用程式主類是可見的。

class MyApp {
    public static void main(String[] args) throws Exception {
        AnnotationConfigApplicationContext appContext =
            new AnnotationConfigApplicationContext(MyConfig.class);
        
        // ready to retrieve beans from appContext, such as myObject.
    }
}

@Configuration
class MyConfig {
    @Bean
    MyObject myObject() {
        // ...configure myObject...
    }

    // ...define more beans...
}

Xml 配置

配置 xml 檔案只需要位於應用程式的類路徑中。

class MyApp {
    public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext appContext =
            new ClassPathXmlApplicationContext("applicationContext.xml");
        
        // ready to retrieve beans from appContext, such as myObject.
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<!-- applicationContext.xml -->
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="myObject" class="com.example.MyObject">
        <!-- ...configure myObject... -->
    </bean>

    <!-- ...define more beans... -->
</beans>

自動裝配

自動裝配需要知道要掃描註釋 bean 的哪些基礎包（@Component）。這是通過 #scan(String...) 方法指定的。

class MyApp {
    public static void main(String[] args) throws Exception {
        AnnotationConfigApplicationContext appContext =
            new AnnotationConfigApplicationContext();
        appContext.scan("com.example");
        appContext.refresh();
        
        // ready to retrieve beans from appContext, such as myObject.
    }
}

// assume this class is in the com.example package.
@Component
class MyObject {
    // ...myObject definition...
}