第四章 构造器注入,自动装配,集合注入

一：控制反转(IOC):就是实例化对象的控制权发生了转变，以前是我们自己new，现在交给spring这个工厂去实例化，如果我现在要用对象，就直接向spring这个工厂索取就可以了。

     两种方式：set方式和构造器方式。

 

二：构造器方式注入

     构造器参数类型的匹配

     要求构造参数非常明确，即参数列表不会有同类型的参数。

     以水果service层为例：

     service层需要持有Dao层对象，才能调用Dao层方法。   

   //Dao层接口： 

package com.spring.chapter4.dao;

public interface FruitDao {
	public void create();
}

   //Dao层实现类：  

package com.spring.chapter4.dao.impl;

import com.spring.chapter4.dao.FruitDao;

public class FruitDaoImpl implements FruitDao {
	public void create() {
		System.out.println("Dao层方法create被调用");
	}
}

   //服务层接口：  

package com.spring.chapter4.service;

public interface FruitService {
	public void create();
}

   //服务层实现类：  

package com.spring.chapter4.service.impl;

import com.spring.chapter4.dao.FruitDao;
import com.spring.chapter4.service.FruitService;

public class FruitServiceImpl implements FruitService {
	private FruitDao fruitDao;

	public FruitServiceImpl(FruitDao fruitDao) {
		super();
		this.fruitDao = fruitDao;
	}

	public void create() {
		fruitDao.create();
	}
}

    这里和我们前面set注入的不同，提供的时我们熟悉的构造方法。

  //配置文件(chapter4.xml) 

<?xml version="1.0" encoding="UTF-8"?>
<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-2.5.xsd">
	<bean id="fruitDao" class="com.spring.chapter4.dao.impl.FruitDaoImpl"/>
	<bean id="fruitService" class="com.spring.chapter4.service.impl.FruitServiceImpl">
		<constructor-arg type="com.spring.chapter4.dao.FruitDao" ref="fruitDao"/>		
	</bean>
</beans>

   //测试类  

package com.spring.chapter4.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.spring.chapter4.service.FruitService;

public class Test {
	public static void main(String[] args) {
		ApplicationContext act = new ClassPathXmlApplicationContext(
				"chapter4.xml");
		FruitService fruitService = (FruitService) act.getBean("fruitService");
		fruitService.create();
	}
}

  

三：构造参数索引：

     可以解决参数同类型问题,并且配置时不用去维护参数顺序的问题,如果使用构造器注入(推荐使用这种方式),或者将前两者结合起来一起使用。

   例如：给服务层添加两个属性      

package com.spring.chapter4.service.impl;

import com.spring.chapter4.dao.FruitDao;
import com.spring.chapter4.service.FruitService;

public class FruitServiceImpl implements FruitService {
	private FruitDao fruitDao;
	private String name;
	private String address;

	public FruitServiceImpl(FruitDao fruitDao) {
		super();
		this.fruitDao = fruitDao;
	}

	public FruitServiceImpl(FruitDao fruitDao, String name, String address) {
		super();
		this.fruitDao = fruitDao;
		this.name = name;
		this.address = address;
	}

	public void create() {
		fruitDao.create();
	}

	public FruitDao getFruitDao() {
		return fruitDao;
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}
}

  //配置文件(chapter4.xml) 

<?xml version="1.0" encoding="UTF-8"?>
<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-2.5.xsd">
	<bean id="fruitDao" class="com.spring.chapter4.dao.impl.FruitDaoImpl"/>
	<bean id="fruitService" class="com.spring.chapter4.service.impl.FruitServiceImpl">	
		<constructor-arg index="0" ref="fruitDao" />		
		<constructor-arg index="1" value="桔子" />
		<constructor-arg index="2" value="中国" />		
	</bean>
</beans>

   //测试类：  

package com.spring.chapter4.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.spring.chapter4.service.FruitService;

public class Test {
	public static void main(String[] args) {
		ApplicationContext act = new ClassPathXmlApplicationContext("chapter4.xml");
		FruitService fruitService = (FruitService) act.getBean("fruitService");
		fruitService.create();
		System.out.println(((FruitServiceImpl)fruitService).getName());
		System.out.println(((FruitServiceImpl)fruitService).getAddress());
	}
}

 

四：集合注入

     Set集合、list集合、properties集合、map集合   

package com.spring.chapter4.service.impl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class CollectionService {
	private Set<String> sets = new HashSet<String>();
	private List<String> lists = new ArrayList<String>();
	private Properties properties = new Properties();
	private Map<String,String> maps = new HashMap<String, String>();
	
	public Set<String> getSets() {
		return sets;
	}
	public void setSets(Set<String> sets) {
		this.sets = sets;
	}
	public List<String> getLists() {
		return lists;
	}
	public void setLists(List<String> lists) {
		this.lists = lists;
	}
	public Properties getProperties() {
		return properties;
	}
	public void setProperties(Properties properties) {
		this.properties = properties;
	}
	public Map<String, String> getMaps() {
		return maps;
	}
	public void setMaps(Map<String, String> maps) {
		this.maps = maps;
	}	
}

  //配置文件(collection.xml)  

<?xml version="1.0" encoding="UTF-8"?>
<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-2.5.xsd">
	<bean id="collectionService" class="com.spring.chapter4.service.impl.CollectionService">
		<property name="sets">
			<set>
				<value>set1</value>
				<value>set2</value>
				<value>set3</value>
			</set>
		</property>
		<property name="lists">
			<list>
				<value>list1</value>
				<value>list2</value>
				<value>list3</value>
			</list>
		</property>
		<property name="properties">
			<props>
				<prop key="key1">properties1</prop>
				<prop key="key2">properties2</prop>
				<prop key="key3">properties3</prop>
			</props>
		</property>
		<property name="maps">
			<map>
				<entry key="key1" value="maps1"/>
				<entry key="key2" value="maps2"/>
				<entry key="key3" value="maps3"/>
			</map>
		</property>
	</bean>
</beans>

   //测试类：  

package com.spring.chapter4.service.impl;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestDemo {
	public static void main(String[] args) {
		ApplicationContext act = new ClassPathXmlApplicationContext("collection.xml");
		CollectionService collectionService = (CollectionService) act.getBean("collectionService");
		Set<String> set = collectionService.getSets();
		for(String s:set){
			System.out.println(s);
		}
		
		List<String> lists = collectionService.getLists();
		for (String s : lists) {
			System.out.println(s);
		}
		
		Properties properties = collectionService.getProperties();
		for (Object key : properties.keySet()) {
			System.out.println(key + ":" + properties.getProperty((String) key));
		}
		
		Map<String, String> mpas = collectionService.getMaps();
		for(String key : mpas.keySet()){
			System.out.println(key + ":" + mpas.get((String) key));
		}
	}
}

 

五：自动装配

   (1). byName   

<?xml version="1.0" encoding="UTF-8"?>
<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-2.5.xsd">
	<bean id="fruitDao" class="dao.impl.FruitDaoImpl" />
	<bean id="fruitService" class="service.impl.FruitServiceImpl"
		autowire="byName" />
</beans>

     需要注意的地方: <bean id="fruitDao" class="dao.impl.FruitDaoImpl" />
id="fruitDao"一定要和服务层的属性名称对应,即FruitDaoImpl类里面一定要有一个名称为fruitDao的属性.

   (2). byType   

<?xml version="1.0" encoding="UTF-8"?>
<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-2.5.xsd">
	<bean id="fruitDao" class="dao.impl.FruitDaoImpl" />
	<bean id="fruitService" class="service.impl.FruitServiceImpl"
		autowire="byType" />
</beans>

      需要保证FruitServiceImpl类中有一个属性类型是FruitDao类型即可.

      尽量不要用自动装配的特性,因为会产生二异性,特别是按类型装配