Spring多种方式实现依赖注入

平常的Java开发中，程序员在某个类中需要依赖其它类的方法。

通常是new一个依赖类再调用类实例的方法，这种开发存在的问题是new的类实例不好统一管理。

Spring提出了依赖注入的思想，即依赖类不由程序员实例化，而是通过Spring容器帮我们new指定实例并且将实例注入到需要该对象的类中。

依赖注入的另一种说法是"控制反转"。通俗的理解是：平常我们new一个实例，这个实例的控制权是我们程序员。

而控制反转是指new实例工作不由我们程序员来做而是交给Spring容器来做。

1.Set注入

构建一个Student对象

package cn.happy.entity;

/**
* Created by CKW on 2017/3/19.
*/
public class Student {
private String sname;
private Integer sage;

public Integer getSage() {
return sage;
}

public void setSage(Integer sage) {
this.sage = sage;
}

public String getSname() {
return sname;
}

public void setSname(String sname) {
this.sname = sname;
}

}

在配置applicationContext.xml中：

<!--set 注入  prototype  原型   singletion  单例-->
<bean id="stu" class="cn.happy.entity.Student" scope="prototype">
<property name="sname" value="张三"></property>
<property name="sage" value="11"></property>
</bean>

测试类中：

//被Spring管理的bean默认都是单例的
@Test
public void myTest1(){
//ac  就是Spring容器
ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
Student stu=(Student) ac.getBean("stu");
Student stu1=(Student) ac.getBean("stu");
System.out.println(stu+"\n"+stu1);
}

2.构造器注入

在对象中添加构造

配置中：

<!--构造注入-->
<bean id="car1" class="cn.happy.entity.Car">
<property name="cname" value="图驴子"></property>
</bean>
<bean id="stu1" class="cn.happy.entity.Student">
<!--(2)创建构造器注入,如果主类有带参的构造方法则需添加此配置-->
<constructor-arg index="0" value="哇哈哈"></constructor-arg>
<constructor-arg index="1" value="11"></constructor-arg>
<constructor-arg index="2" ref="car1"></constructor-arg>
</bean>

测试类：

//构造注入
@Test
public void myTest2(){
ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
Student stu1=(Student) ac.getBean("stu1");
Student stu2=(Student) ac.getBean("stu2");
System.out.println("构造："+stu1);

}

3.空间命名注入

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
">

<!--命名空间P注入-->
<bean id="car2" class="cn.happy.entity.Car">
<property name="cname" value="毛驴"></property>
</bean>
<bean id="stu2" class="cn.happy.entity.Student" p:sname="李四" p:sage="18" p:car-ref="car2"></bean>

//构造注入   命名空间注入
@Test
public void myTest2(){
ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
Student stu1=(Student) ac.getBean("stu1");
Student stu2=(Student) ac.getBean("stu2");
System.out.println("构造："+stu1+"\n命名空间："+stu2);

}

4.集合注入

<!--list集合属性注入-->
<bean id="collection1" class="cn.happy.entity.MyCollection">
<property name="list">
<list>
<value>哈哈</value>
<value>呵呵</value>
<value>嘿嘿</value>
</list>
</property>
</bean>

<!--set集合属性注入-->
<bean id="collection2" class="cn.happy.entity.MyCollection">
<property name="set">
<set>
<value>哈哈</value>
<value>呵呵</value>
<value>嘿嘿</value>
</set>
</property>
</bean>

<!--Map集合属性注入-->
<bean id="collection3" class="cn.happy.entity.MyCollection">
<property name="map">
<map>
<entry key="001">
<value>呵呵</value>
</entry>
<entry key="002">
<value>哈哈</value>
</entry>
<entry key="003">
<value>嘿嘿</value>
</entry>
</map>
</property>
</bean>

5.注解注入

package cn.happy.entity;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;

/**
* Created by CKW on 2017/3/22.
*/
@Component("car") //不分层
/*@Repository  //dao层*/
/*@Service  //biz层*/
/*@Controller  //action层*/
public class Car {
@Value("特斯拉")
private String cname;

@Override
public String toString() {
return getCname();
}

public Car() {
}

public Car(String cname) {
this.cname = cname;
}

public String getCname() {
return cname;
}

public void setCname(String cname) {
this.cname = cname;
}
}

package cn.happy.entity;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;

/**
* Created by CKW on 2017/3/22.
*/

@Component("student")
public class Student {
@Value("撒打发")
private String sname;
@Value("20")
private Integer sage;
//jdk注解
//    @Resource
@Autowired
@Qualifier("car")
private Car car;

@Override
public String toString() {
return "name="+getSname()+",age="+getSage()+",car="+getCar();
}

public Car getCar() {
return car;
}

public void setCar(Car car) {
this.car = car;
}

public Student() {

}

public String getSname() {
return sname;
}

public Student(String sname, Integer sage, Car car) {
this.sname = sname;
this.sage = sage;
this.car = car;
}

public void setSname(String sname) {
this.sname = sname;
}

public Integer getSage() {
return sage;
}

public void setSage(Integer sage) {
this.sage = sage;
}
}

在配置applicationContext.xml中：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
">

<!--注解-->
<!--配置包扫描器-->
<context:component-scan base-package="cn.happy.entity"></context:component-scan>

测试类：

//注解
@Test
public void myTest4(){
ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
Student stu=(Student)ac.getBean("student");
System.out.println(stu.getCar().getCname());
}