（006）spring之AnnotationConfigApplicationContext的3种构造方式

　　AnnotationConfigApplicationContext是spring中利用注解配置的方式构建spring上下文的类。

　　第一种方式：构造函数传入一个或者多个类。可以是注解类，也可以是普通类，传入的类都会纳入到spring容器中。如下：

　　pom.xml

<?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>

    <groupId>com.edu.spring</groupId>
    <artifactId>spring</artifactId>
    <version>1.0.0</version>

    <name>spring</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
    </dependencies>

</project>

　　User.java、Cat.java、Dog.java、UserDao.java、UserService.java、MyConfig.java如下：

package com.edu.spring;

public class User {

}


package com.edu.spring;

public class Cat {

}


package com.edu.spring;

public class Dog {

}


package com.edu.spring;

import org.springframework.stereotype.Component;

@Component
public class UserDao {

}


package com.edu.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;

@Service
public class UserService {
    
    @Bean
    public Cat createCat(){
        return new Cat();
    }
}


package com.edu.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    
    @Bean
    public Dog createDog(){
        return new Dog();
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(User.class,UserDao.class,UserService.class,MyConfig.class);
        System.out.println(context.getBean(User.class));
        System.out.println(context.getBean(Cat.class));
        System.out.println(context.getBean(Dog.class));
        System.out.println(context.getBean(UserDao.class));
        System.out.println(context.getBean(UserService.class));
        System.out.println(context.getBean(MyConfig.class));
        context.close();
        
    }
}

　　运行结果如下：

 　　第二种方式：构造函数传入一个包名，该包下的类都会创建bean，并且纳入spring容器中

　　App.java，User.class没有加注解，不会创建bean

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext("com.edu.spring");
       // System.out.println(context.getBean(User.class));
        System.out.println(context.getBean(Cat.class));
        System.out.println(context.getBean(Dog.class));
        System.out.println(context.getBean(UserDao.class));
        System.out.println(context.getBean(UserService.class));
        System.out.println(context.getBean(MyConfig.class));
        context.close();
        
    }
}

　　运行结果如下：

 　　第三种方式：构造函数传入一个加了@ComponentScan注解的类，该注解指明了扫描的包和排除掉的类

　　AnnotationScan.java

package com.edu.spring;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.context.annotation.FilterType;

@ComponentScan(basePackages="com.edu.spring",
               excludeFilters=@Filter(type=FilterType.ASSIGNABLE_TYPE,classes={MyConfig.class,UserService.class}))
public class AnnotationScan {

}

　　App.java 代码中注销掉的类都不会创建bean，因为排除掉了

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(AnnotationScan.class);
        //System.out.println(context.getBean(User.class));
        //System.out.println(context.getBean(Cat.class));
        //System.out.println(context.getBean(Dog.class));
        System.out.println(context.getBean(UserDao.class));
        //System.out.println(context.getBean(UserService.class));
        //System.out.println(context.getBean(MyConfig.class));
        context.close();
        
    }
}

　　运行结果如下：