Spring实战-装配Bean三种方法

Spring-Bean的装配的三种方式

1. 自动化装配

2. 创建被发现的bean

@Component 告知Spring为这个类创建bean

org.springframework.stereotype.Component; 在spring-content-4.1.6.RELEASE.jar中

import org.springframework.stereotype.Component;

@Component
public class User{ }

3. 启动组件扫描

@Configuration 声明为配置类

@ComponentScan默认扫描与配置类相同的包及子包

可以添加属性值 basePackages={“people”}

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

@Configuration
@ComponentScan
public class build {	}

4. 测试组件

SpringJUnit4ClassRunner 自动创建Spring应用上下文

@ContextConfiguration 加载配置

@Autowired 自动装配

自动满足bean依赖，自动注入适配bean，required=false 让这个bean处于未装配状态，如果有多个bean满足依赖关系，@Qualifer(“..”) 缩小范围，达到只有一个bean满足规定的限制条件

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=build.class)
public class Main {

	@Autowired
	User user;	
	
	@Test
	public void test(){
		assertNotNull(user);
		System.out.println(user.toString());
	}
}

❌错误：

java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory

导入 commons-logging-1.2.jar

java.lang.NoClassDefFoundError: org/aopalliance/aop/Advice

导入 aopalliance-1.0.jar

最终输出

User [id=0, name=null]

5. 接口装配bean

import org.springframework.stereotype.Component;

@Component
public interface People {
	void method(int a);
}

而实现类实现接口

import org.springframework.stereotype.Component;

@Component
public class Method implements People{
	
	public void method(int a){
		System.out.println("create....."+a);
	}
}

测试方法可以得到实现类结果

import static org.junit.Assert.assertNotNull;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;


@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=Config.class)
public class Main {
	@Autowired
	People people;
	@Test
	public void test(){
		people.method(3); //create.....3
		assertNotNull(people);		
	}
}

6. java代码装配

@Bean 创建一个bean实例并将其注入到Spring应用上下文中

@Bean
public User setUser()
{
  return new User();
}

7. xml装配

@Configuration
@ComponentScan
public class build {
	
	User user;
	public build(){}
	
	public build(User user){
		user.setId(3);	
		this.user = user;
	}

}

<bean id = "user" class="com.runaccpeted.test.User"></bean>
<bean id = "b" class="com.runaccpeted.test.build">
    <constructor-arg ref="user"></constructor-arg>
</bean>

当构造器参数注入集合时

<bean id = "build" class="com.runaccpeted.test.Build">
  <constructor-arg>
    <list>
      <ref bean="user"></ref>
    </list>
  </constructor-arg>
</bean>

set方法注入

<bean id = "build" class="com.runaccpeted.test.Build">
  <property name="user" ref="user"></property>
</bean>

工作

ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("application.xml");
		build b = context.getBean(build.class);
		System.out.println(b.user.toString());
		context.close();

8. 混合装配bean

javaConfig+xml

@Import(User.class) xml中拥有User的beanID

<bean id = "user" class="com.runaccpeted.test.User"></bean>

@Configuration
@Import(User.class)
public class Config{
  @Bean
  public build setBuild(){
    return new build(user);
  }  
}

9. bean的scope

spring中bean创建默认是单例的 scope=”singleton”

prototype 每次调用创建新实例

request 每个请求重新实例化

session 每个会话

application

global session Spring中的对象，依赖于spring-webmvc-portlet.jar