Spring_002 依赖注入方式实现
一、Spring的依赖注入（DI）
在Spring框架下，当Bean实例A运行过程中需要引用另外一个Bean实例B时，Spring框架会创建Bean的实例B，并将实例B通过实例A的构造函数、set方法、自动装配和注解方式注入到实例A，这种注入实例Bean到另外一个实例Bean的过程叫做依赖注入。
依赖注入的好处就是尽可能隔离Bean之间的代码耦合，提高Bean重用的可能性，并尽量降低程序代码的维护难度，Spring框架通过依赖注入技术将不同的Bean融合起来，完成复杂业务操作，但又确保了每个Bean相对的独立性。
Spring框架提供构造函数注入、设置方法注入、自动装配注入和注解注入四种注入方式。
1、基于构造函数的依赖注入
BybService.java
public class BybService {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "BybService{" +
"name='" + name + '\'' +
'}';
}
public String sayByb(){
System.out.println("Byb"+name);
return "Byb"+name;
}
}
HelloWorld.java
public class HelloWorld {
private String message;
private BybService bybService;
public HelloWorld(BybService bybService) {
this.bybService=bybService;
}
public void setMessage(String message) {
this.message = message;
}
public void getMessage() {
System.out.println("message : " + message);
}
public void sayHello(){
System.out.println(bybService.sayByb());
}
}
Bean.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.xsd">
<bean id="helloWorld" class="HelloWorld">
<constructor-arg ref="BybService"></constructor-arg>
</bean>
<bean id="BybService" class="BybService">
<property name="name" value="Hello World!" />
</bean>
</beans>
Main.App
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args){
ApplicationContext context = new ClassPathXmlApplicationContext("Bean.xml");
HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
BybService bybService=(BybService) context.getBean("BybService");
obj.sayHello();
}
}
运行MainApp.java
2、基于set方法注入（属性注入）
HelloWorld.java
public class HelloWorld {
private String message;
private BybService bybService;
public void setMessage(String message) {
this.message = message;
}
public void getMessage() {
System.out.println("message : " + message);
}
public void sayHello(){
System.out.println(bybService.sayByb());
}
public BybService getBybService() {
return bybService;
}
public void setBybService(BybService bybService) {
this.bybService = bybService;
}
}
BybService.java
public class BybService {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "BybService{" +
"name='" + name + '\'' +
'}';
}
public String sayByb(){
System.out.println("Byb"+name);
return "Byb"+name;
}
}
Bean.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.xsd">
<bean id="helloWorld" class="HelloWorld">
<property name="message" value="Hello World!" />
<property name="BybService" ref="BybService"></property>
</bean>
<bean id="BybService" class="BybService">
<property name="name" value="Hello World!" />
</bean>
</beans>
MainApp.java
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args){
ApplicationContext context = new ClassPathXmlApplicationContext("Bean.xml");
HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
BybService bybService=(BybService) context.getBean("BybService");
obj.sayHello();
}
}
运行MainApp.java
3、注解注入
Bean.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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<context:annotation-config />
<bean id="helloWorld" class="HelloWorld">
<property name="message" value="aaa!" />
</bean>
<bean id="BybService" class="BybService">
<property name="name" value="Hello World!" />
</bean>
</beans>
BybService.java
public class BybService {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "BybService{" +
"name='" + name + '\'' +
'}';
}
public String sayByb(){
System.out.println("Byb"+name);
return "Byb"+name;
}
}
HelloWorld.java
import org.springframework.beans.factory.annotation.Autowired;
public class HelloWorld {
private String message;
@Autowired
private BybService bybService;
public void setMessage(String message) {
this.message = message;
}
public void getMessage() {
System.out.println("message : " + message);
}
public void sayHello(){
System.out.println(bybService.sayByb());
}
}
MainApp.java
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args){
ApplicationContext context = new ClassPathXmlApplicationContext("Bean.xml");
HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
BybService bybService=(BybService) context.getBean("BybService");
obj.sayHello();
//bybService.sayByb();
}
}
运行结果如下：
二、Spring注入依赖的时间
Spring在创建beanFactory实例化类的时候，先加载类，然后调用类的构造器进行初始化，在完成初始化进行依赖注入（常见的就是set注入，通过执行set方法）。
三、使用eclipse创建注入Bean实例
继续写我们的第一个Spring程序，这次我们使用依赖注入的方式实现程序
第一步，建立我们的Spring_002程序，并在程序中添加BookDao.java、BookDaoImpl.java、BookService.java、BookServiceImpl.java、
ApplicationContext.xml
第二步 在BookDao接口中配置一个addBook方法
package com.zk.myspring;
public interface BookDao {
public void addBook();
}
在BookDaoImpl中实现addBook方法
package com.zk.myspring;
public class BookDaoImpl implements BookDao{
@Override
public void addBook() {
// TODO Auto-generated method stub
System.out.println("addBook");
}
}
在BookService接口中配置addBook方法
package com.zk.myspring;
public interface BookService {
public abstract void addBook();
}
在BookServiceImpl方法中实现addBook方法
package com.zk.myspring;
public class BookServiceImpl implements BookService{
//方式一：接口等于实现类
//private BookDao bookDao=new BookDaoImpl();
//方式二：接口+set方法
private BookDao bookdao;
public void setBookdao(BookDao bookdao) {//依赖注入
this.bookdao = bookdao;
}
@Override
public void addBook() {
// TODO Auto-generated method stub
//this.bookdao.addBook();
System.out.println("add book");
}
}
注意在BookServiceImpl文件中，我们使用接口+set方法实现，并在setBookdao方法中实现依赖注入，使得BookService依赖于BookDao
第三步 配置我们的ApplicationContext.xml，使用property属性将BookDao注入进BookService
<property name="bookdao" ref="bookDaoId"></property>
<property> 用于属性注入
name:bean的属性名，通过setter方法获得
ref:另一个bean的id值的引用
<?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:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
<!-- 创建Dao -->
<!-- 模拟spring执行过程
创建Service实例:BookService bookservice=new BookServiceImpl(); IOC <bean>
创建Dao实例:BookDao bookDao=new BookDaoImpl(); IOC
将dao设置给service:bookservice.setBookDao(bookDao); DI <property>
<property> 用于属性注入
name:bean的属性名，通过setter方法获得
ref:另一个bean的id值的引用
-->
<!--创建Dao -->
<bean id="bookDaoId" class="com.zk.myspring.BookDaoImpl"></bean>
<!-- 创建service -->
<bean id="bookServiceId" class="com.zk.myspring.BookServiceImpl">
<property name="bookdao" ref="bookDaoId"></property>
</bean>
</beans>
第四步 创建一个test方法，对配置文件进行测试
package com.zk.myspring;
import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
public class TestBook {
public static void main(String[]args)
{
//从spring容器中获得
String path="ApplicationContext.xml";
ApplicationContext ac=new ClassPathXmlApplicationContext(path);
BookService bs=(BookService) ac.getBean("bookServiceId");
bs.addBook();
}
@Test
public void test1(){
//使用BeanFactory实例化
String path="ApplicationContext.xml";
BeanFactory bf=new XmlBeanFactory(new ClassPathResource(path));
BookService bs=(BookService) bf.getBean("bookServiceId");
bs.addBook();
}
}
得出输出
依赖注入方式配置spring成功
三、使用ideal创建Spring依赖注入实例
首先创建一个Spring项目
创建BybService.java、HelloWorld.java、MainApp.java和资源文件Bean.xml
BybService.java
public class BybService {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "BybService{" +
"name='" + name + '\'' +
'}';
}
public void sayByb(){
System.out.println("Byb"+name);
}
}
HelloWorld.java
public class HelloWorld {
private String message;
private BybService bybService;
public void setMessage(String message) {
this.message = message;
}
public void getMessage() {
System.out.println("message : " + message);
bybService.sayByb();
}
public BybService getBybService() {
return bybService;
}
public void setBybService(BybService bybService) {
this.bybService = bybService;
}
}
MainApp.java
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args){
ApplicationContext context = new ClassPathXmlApplicationContext("Bean.xml");
HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
BybService bybService=(BybService) context.getBean("BybService");
obj.getMessage();
bybService.sayByb();
}
}
Bean.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.xsd">
<bean id="helloWorld" class="HelloWorld">
<property name="message" value="Hello World!" />
<property name="bybService" ref="BybService"></property>
</bean>
<bean id="BybService" class="BybService">
<property name="name" value="Hello World!" />
</bean>
</beans>
Spring容器可以配置Bean，注入属性，而且可以维护Bean与Bean之间的关系。
<bean>标签的作用是当spring框架加载的时候，spring会自动创建一个bean，并放入内存。当ApplicationContext context = new ClassPathXmlApplicationContext("Bean.xml");执行的时候，Spring容器就会被创建，同时applicationContext.xml中配置，Bean就会被创建放入（内存[HashMap/HashTable]）中。
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