day38 18-Spring的XML和注解的结合使用

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什么情况下使用XML,什么情况下使用注解?又有XML,又有注解,开发的时候使用哪种?

XML:结构清晰,配置麻烦.

注解:简单,

它俩的结合点在属性注入上.

两种方式结合:一般使用XML注册Bean,使用注解进行属性的注入.

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package cn.itcast.spring3.demo1;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.annotation.Resource;

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

/**
 * 注解的方式装配Bean.
 * @author zhongzh
 *
 */
//在Spring配置文件中<bean id="userService" class="cn.itcast.demo1.UserService">
//其实也需要核心配置文件,只不过不是用来装配bean了,你得告诉Spring需要去哪些包下面去扫描.它得扫描到这些注解才行.它得去哪里扫描你得告诉人家才行
//@Component(value="userService")
//@Component("userService")
@Service(value="userService")//Service层,默认把这个类UserService交由Spring来管理了

//@Scope(value="")//Scope的默认值是单例的
@Scope(value="prototype")//Scope,多例,默认值都是单例的.
public class UserService {
    //如果是普通属性,可以使用value注解来注入了
    @Value(value="itcast")
    private String info;
    //@Autowired//如果是复杂类型或者是对象属性使用@Autowired这个注解:自动装配默认使用类型注入.
    //@Autowired(required=false)//AutoWired的属性required=false忽略异常。默认required=true出异常就终止了.required=false依然可以注入,但是出异常的话注入的是null值.
    //required属性出异常不管了,required=false出异常程序照样往下执行,成不成功另外说了.默认required=true,有异常就不注入就停止了.
    //@Qualifier("userDao")
    //@Autowired(required=true)//默认,一般不去改这个值
    //@Qualifier("uDao")//按名称注入,@AutoWired+@Qualifier()
    @Resource(name="userDao")//等于@AutoWired+@Qualifeied,按名称注入
    private UserDao userDao;
     public void sayHello(){

         //System.out.println("Hello Spring Annotation.....");
         System.out.println("Hello Spring Annotation....."+info);
     }
    //@Override
//    public String toString() {
//        return "UserService [info=" + info + ", userDao=" + userDao + "]";
//    }

    @PostConstruct   //初始化
    public void setup(){
        System.out.println("初始化.....");
    }
    @PreDestroy
    public void teardown(){
        System.out.println("销毁......");//销毁只对单例有效,多例就没有输出.
    }
}

package cn.itcast.spring3.demo1;

//import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;

//Dao这个类正常也应该交由Spring管理.
//@Component
//@Repository//按类型注入
@Repository("userDao")//按名称注入

public class UserDao {

}

package cn.itcast.spring3.demo1;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

//注解的方式:都是将类装载到容器中.
public class SpringTest1 {
   @Test
   public void demo1(){

      //ApplicationContext  applicationContext  = new ClassPathXmlApplicationContext("applicationContext.xml");
       ClassPathXmlApplicationContext  applicationContext  = new ClassPathXmlApplicationContext("applicationContext.xml");
      UserService userService = (UserService) applicationContext.getBean("userService");
      //userService.sayHello();
       System.out.println(userService);

       UserService userService2 = (UserService) applicationContext.getBean("userService");

       System.out.println(userService2);//注入了一个dao,dao是一样的.不是Service创建是一样的.
       //多例的话是初始化两次.每次输出的Service地址都是不一样的.
       applicationContext.close();//销毁只对单例有效.多例就没有输出销毁.
   }

}

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package cn.itcast.spring3.demo2;

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

//配置信息
@Configuration//代表BeanConfig是一个配置类.
//一般很少使用BeanConfig,除非类的构造特别复杂.在核心配置文件中配置起来或者是用注解的方式写起来比较麻烦的时候才会使用BeanConfig这种方式.
//类越多越能看出这种方式的好处.一个类是看不出来的.
public class BeanConfig {

    //@Bean
    @Bean(name="car")

     public Car showCar(){
         Car car = new Car();
         car.setName("长安");
         car.setPrice(40000d);

         return car;

     }

    //@Bean
    @Bean(name="product")

     public Product initPorduct(){
        Product product = new Product();
        product.setName("空调");
        product.setPrice(3000d);

        return product;

     }
}

package cn.itcast.spring3.demo2;

public class Car {
   private String name;
   private Double price;
/*public String getName() {
    return name;
}*/
public void setName(String name) {
    this.name = name;
}
/*public Double getPrice() {
    return price;
}*/
public void setPrice(Double price) {
    this.price = price;
}
@Override
public String toString() {
    return "Car [name=" + name + ", price=" + price + "]";
}

}

package cn.itcast.spring3.demo2;

public class Product {
   private String name;
   private Double price;
/*public String getName() {
    return name;
}*/
public void setName(String name) {
    this.name = name;
}
/*public Double getPrice() {
    return price;
}*/
public void setPrice(Double price) {
    this.price = price;
}
@Override
public String toString() {
    return "Product [name=" + name + ", price=" + price + "]";
}

}

package cn.itcast.spring3.demo2;

import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringTest {
    @Test
    public void demo1(){
     ClassPathXmlApplicationContext  applicationContext  = new ClassPathXmlApplicationContext("applicationContext.xml");

     Car car = (Car) applicationContext.getBean("car");
     Product product = (Product) applicationContext.getBean("product");

    System.out.println(car);
    System.out.println(product);

    }
}

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package cn.itcast.spring3.demo3;

public class CustomerDao {

}

package cn.itcast.spring3.demo3;

public class OrderDao {

}

package cn.itcast.spring3.demo3;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

public class CustomerService {

    private CustomerDao customerDao;
    @Autowired
    @Qualifier("orderDao")//按名称注入.
    //这两个注解可以作用在属性上,也可以作用在setter方法上.
    //作用在属性上可以没有setter方法.
    private OrderDao   orderDao;
/*    public CustomerDao getCustomerDao() {
        return customerDao;
    }*/
    public void setCustomerDao(CustomerDao customerDao) {
        this.customerDao = customerDao;
    }
/*    public OrderDao getOrderDao() {
        return orderDao;
    }*/
/*    public void setOrderDao(OrderDao orderDao) {
        this.orderDao = orderDao;
    }*/
    @Override
    public String toString() {
        return "CustomerService [customerDao=" + customerDao + ", orderDao="
                + orderDao + "]";
    }

}

package cn.itcast.spring3.demo3;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringTest3 {
     @Test

     public void demo1(){
        ApplicationContext  applicationContext  = new ClassPathXmlApplicationContext("applicationContext2.xml");

         CustomerService customerService = (CustomerService) applicationContext.getBean("customerService");

       System.out.println(customerService);

     }

}

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<?xml version="1.0" encoding="UTF-8"?>
<!-- 基于注解的开发需要引入context命名空间。它就是用来配置去扫描哪些包的. -->
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:p="http://www.springframework.org/schema/p"
       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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    <!--
    context:component-scan标签不用加,因为这个标签是用来扫描类上的注解的.
           例如@Component等等..但是这些类已经由XML注册了,所以不用使用这个标签了.

    <context:component-scan base-package=""></context:component-scan>
    -->
    <!--  context:annotation-config标签是使得@AutoWired、@Qualifier、@Resource、@PostConstruct、@PreDestroy等标签生效.-->
    <context:annotation-config></context:annotation-config><!--  -->
   <bean id="customerDao" class="cn.itcast.spring3.demo3.CustomerDao"></bean>
   <bean id="orderDao" class="cn.itcast.spring3.demo3.OrderDao"></bean>

    <bean  id="customerService"  class="cn.itcast.spring3.demo3.CustomerService">
            <property name="customerDao" ref="customerDao"></property>
            <!--
            <property name="orderDao" ref="orderDao"></property>
            -->
    </bean>
</beans>

<?xml version="1.0" encoding="UTF-8"?>
<!-- 基于注解的开发需要引入context命名空间。它就是用来配置去扫描哪些包的. -->
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:p="http://www.springframework.org/schema/p"
       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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
<context:annotation-config></context:annotation-config><!-- XML和注解混搭的时候用的 -->
<!-- 告诉Spring你要扫描哪些包下的东西 -->
<!--
<context:component-scan base-package="cn.itcast.spring3.demo1">

-->
<!--
<context:component-scan base-package="cn.itcast.spring3.demo1,cn.itcast.spring3.demo2">
-->
<context:component-scan base-package="cn.itcast.spring3">
<!-- 纯注解用扫描的就行 -->

</context:component-scan>

</beans>