基础框架 Spring框架bean注入的几种方式

一、概念

spring bean的注入大致分为两类：XML配置 与 注解方式
XML配置：set注入、构造函数注入，P标签，静态工厂方法与实例工厂方法；
注解方式： @Autowired,@Resource,@Qualifier。

注解需要注意：
@Autowired：是自动装配，默认采用类型ByType，依赖对象必须存在，否则抛出异常，如果要允许null 值，可以设置它的required属性为false，如：@Autowired(required=false) 。

@Qualifier("cusInfoService")：根据名称装配，一般与Autowired结合使用。

@Resource(name="cusInfoService")：默认根据名称，可以指定名称或类型，也可以同时指定。
@Resource装配顺序
1. 如果同时指定了name和type，则从Spring上下文中找到唯一匹配的bean进行装配，找不到则抛出异常
2. 如果指定了name，则从上下文中查找名称（id）匹配的bean进行装配，找不到则抛出异常
3. 如果指定了type，则从上下文中找到类型匹配的唯一bean进行装配，找不到或者找到多个，都会抛出异常
4. 如果既没有指定name，又没有指定type，则自动按照byName方式进行装配；如果没有匹配，则回退为一个原始类型进行匹配，如果匹配则自动装配；

注解方式注意：
@Configuration：标识配置类，相当于spring配置文件
@ComponentScan("com.hello.bean")：扫描包路径。

@Component：用来标识一个bean，用于spring的IOC容器就是通过扫描加注解的方式将对象放入容器管理。

@Component细分@Controller，@Service，@Repository，只是为了分类，作用相同！
@Controller("Bean的名称")：定义控制层Bean,如Action
@Service("Bean的名称")：定义业务层Bean
@Repository("Bean的名称")：定义DAO层Bean

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二、案例

1. xml配置

   /**

   • 书

   • @author zrj

   • @date 2020/12/16

   • @since V1.0 **/ public class Book { private String bookName; private String bookAuthor;

     public Book() { }

     public Book(String bookName, String bookAuthor) { this.bookName = bookName; this.bookAuthor = bookAuthor; }

     public String getBookName() { return bookName; }

     public void setBookName(String bookName) { this.bookName = bookName; }

     public String getBookAuthor() { return bookAuthor; }

     public void setBookAuthor(String bookAuthor) { this.bookAuthor = bookAuthor; }

     @Override public String toString() { return "Book{" + "bookName='" + bookName + ''' + ", bookAuthor='" + bookAuthor + ''' + '}'; } } 1234567891011121314151617181920212223242526272829303132333435363738394041424344

   /**

   • 订单类

   • @author zrj

   • @date 2020/12/17

   • @since V1.0 **/ public class Orders { private String orderName; private double orderPrice;

     public Orders() { }

     public Orders(String orderName, double orderPrice) { this.orderName = orderName; this.orderPrice = orderPrice; }

     public String getOrderName() { return orderName; }

     public void setOrderName(String orderName) { this.orderName = orderName; }

     public double getOrderPrice() { return orderPrice; }

     public void setOrderPrice(double orderPrice) { this.orderPrice = orderPrice; }

     @Override public String toString() { return "Orders{" + "orderName='" + orderName + ''' + ", orderPrice=" + orderPrice + '}'; } } 1234567891011121314151617181920212223242526272829303132333435363738394041424344

   /**

   • 汽车

   • @author zrj

   • @date 2020/12/16

   • @since V1.0 **/ public class Car { private String carName; private String carAuthor;

     public Car() { }

     public Car(String carName, String carAuthor) { this.carName = carName; this.carAuthor = carAuthor; }

     public String getCarName() { return carName; }

     public void setCarName(String carName) { this.carName = carName; }

     public String getCarAuthor() { return carAuthor; }

     public void setCarAuthor(String carAuthor) { this.carAuthor = carAuthor; }

     @Override public String toString() { return "Car{" + "carName='" + carName + ''' + ", carAuthor='" + carAuthor + ''' + '}'; } }

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   /**

   • 工厂注入

   • @author zrj

   • @date 2020/12/17

   • @since V1.0 **/ public class CarFactory {

     /**

     • 静态工厂，返回一个Car的实例对象 */ public static Car getCar() { return new Car( "奔驰", "梅赛德斯你" ); }

     /**

     • 实例工厂，返回一个Car的实例对象 */ public Car getNewCar() { return new Car( "帕梅拉", "保时捷" ); } } 123456789101112131415161718192021222324

   <!--1 set方法注入属性-->
   <bean id="book" class="com.spring5.bean.Book">
       <!--使用property完成属性注入，name：类里面属性名称,value：向属性注入的值 -->
       <property name="bookName" value="平凡世界"></property>
       <property name="bookAuthor" value="路遥"></property>
   </bean>
   
   <!--2 有参数构造注入属性-->
   <bean id="orders" class="com.spring5.bean.Orders">
       <constructor-arg name="orderName" value="电脑"></constructor-arg>
       <constructor-arg name="orderPrice" value="12"></constructor-arg>
   </bean>
   
   <!--3 p标签注入-->
   <bean id="car" class="com.spring5.bean.Car" p:carName="幻影" p:carAuthor="劳斯莱斯"/>
   
   <!--4 静态工厂注入-->
   <bean id="car2" class="com.spring5.bean.CarFactory" factory-method="getCar"/>
   
   <!--5 实例工厂注入-->
   <bean id="carFactory" class="com.spring5.bean.CarFactory"/>
   <bean id="cars" factory-bean="carFactory" factory-method="getNewCar"/>
   

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   package com.spring5.test;

   import com.spring5.bean.Book; import com.spring5.bean.Car; import com.spring5.bean.Orders; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;

   /**

   • spring测试类

   • @author zrj

   • @date 2020/12/13

   • @since V1.0 **/ public class SpringTest {

     /**

     • 加载spring配置文件 */ ApplicationContext context = new ClassPathXmlApplicationContext( "bean1.xml" );

     /**

     • set注入 */ @Test public void bookTest() { Book book = context.getBean( "book", Book.class ); System.out.println( book.toString() ); }

     /**

     • 构造函数 */ @Test public void orderTest() { Orders order = context.getBean( "orders", Orders.class ); System.out.println( order.toString() ); }

     /**

     • p空间注入 */ @Test public void curTest() { Car car = context.getBean( "car", Car.class ); System.out.println( car.toString() ); }

     /**

     • 静态工厂注入 */ @Test public void curTest2() { Car car = context.getBean( "car2", Car.class ); System.out.println( car.toString() ); }

     /**

     • 实例工厂注入 */ @Test public void curTest3() { Car car = context.getBean( "cars", Car.class ); System.out.println( car.toString() ); } }

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2. 注解方式

   package com.hello.config;

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

   /**

   • springBean配置类
   • @author 20023262
   • @date 2020/12/18
   • @since 1.0 */ @Configuration @ComponentScan("com.hello.bean") public class SpringBeanConfiguration { }

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   package com.hello.bean;

   import lombok.*; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component;

   /**

   • 汽车
   • @author 20023262
   • @date 2020/12/18
   • @since 1.0 */ @Data @Builder @ToString @Scope(value = "prototype") @Component(value = "car") public class Car { private String name; private String auth; }

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   package com.hello.bean;

   import lombok.Builder; import lombok.Data; import lombok.ToString; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component;

   /**

   • 电脑
   • @author 20023262
   • @date 2020/12/18
   • @since 1.0 */ @Data @Builder @ToString @Scope(value = "prototype") @Component(value = "computer") public class Computer { private String brand; private String name; }

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   package com.hello.bean;

   import lombok.Builder; import lombok.Data; import lombok.ToString; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component;

   /**

   • 手机
   • @author 20023262
   • @date 2020/12/18
   • @since 1.0 */ @Data @Builder @ToString @Scope(value = "prototype") @Component(value = "mobile") public class Mobile { private String brand; private String name; }

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   package com.hello.bean;

   import lombok.Builder; import lombok.Data; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component;

   import javax.annotation.Resource;

   /**

   • 用户类

   • Component(value = "user") //相当于在配置文件中　

   • Scope(value = "prototype") //配置创建对象是否是以单列模式进行创建

   • Autowired：自动装配，默认按type注入

   • Resource(name = "book")：默认按name注入，可以通过name和type属性进行选择性注入

   • Qualifier：按照名称装配

   • @author 20023262

   • @date 2020/12/18

   • @since 1.0 */ @Scope(value = "prototype") @Component(value = "user") public class User { private String name; private int age;

     @Autowired(required = false) private Car car;

     @Resource(name = "mobile") private Mobile mobile;

     @Qualifier("computer") @Autowired(required = false) private Computer computer;

     public User() { }

     public User(String name, int age, Car car, Mobile mobile, Computer computer) { this.name = name; this.age = age; this.car = car; this.mobile = mobile; this.computer = computer; }

     public String getName() { return name; }

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

     public int getAge() { return age; }

     public void setAge(int age) { this.age = age; }

     public Car getCar() { return car; }

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

     public Mobile getMobile() { return mobile; }

     public void setMobile(Mobile mobile) { this.mobile = mobile; }

     public Computer getComputer() { return computer; }

     public void setComputer(Computer computer) { this.computer = computer; }

     @Override public String toString() { return "User{" + "name='" + name + ''' + ", age=" + age + ", car=" + car + ", mobile=" + mobile + ", computer=" + computer + '}'; } }

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   package com.hello.bean;

   import com.hello.config.SpringBeanConfiguration; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.AnnotationConfigApplicationContext;

   /**

   • springBean注解注入测试类

   • @author 20023262

   • @date 2020/12/18

   • @since 1.0 */ public class SpringBeanTest {

     @Test public void springBeanTest() { // 加载配置类 ApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringBeanConfiguration.class); User user = applicationContext.getBean("user", User.class); System.out.println("user：" + user);

     }

   }

总结：

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