Spring-IOC配置(学习笔记)

• Instantiating beans

  
  

1. instantiation with a constructor

<bean id = "car" class = "com.jiakai.spring.Car"/>

public class Car {public Car(){System.out.println("make car with default");}public void run(){System.out.println("the car run on the road");}}

此时创建bean的时候,会调用class属性中类的,无参数的构造方法.

2.   Instantiation with a static factory method

<bean id = "car" class = "com.jiakai.spring.BMW" factory-method = "createCar"/>

public class Car {private String name;public Car(){System.out.println("make car with default");}public void run(){System.out.println(name+" car run on the road");}public String getName() {return name;}public void setName(String name) {this.name = name;}}

public class BMW {public static Car createCar(){Car car = new Car();car.setName("bmw");System.out.println("make car with BMW static factory method");return car;}}

此时,会调用class属性中的类的,静态的,factory-method方法创建对象.

如果factory-method方法有参数,可以利用constructor-arg来设定.

<bean id = "car" class = "com.jiakai.spring.BMW" factory-method = "createCar"><constructor-arg name="msg" value="have args"/><constructor-arg name="level" value="55"/></bean>

package com.jiakai.spring;public class BMW {public static Car createCar(String msg,int level){System.out.println(msg);System.out.println(level);Car car = new Car();car.setName("bmw");System.out.println("make car with BMW static factory method");return car;}}

3.Instantiation using an instance factory method

 <bean id = "bmw" class = "com.jiakai.spring.BMW"/>           <bean id = "car" factory-bean = "bmw" factory-method = "createCar"><constructor-arg name="msg" value="have args"/><constructor-arg name="level" value="55"/></bean>

public class BMW {public Car createCar(String msg,int level){System.out.println(msg);System.out.println(level);Car car = new Car();car.setName("bmw");System.out.println("make car with BMW object factory method");return car;}}

此时,会调用factory-bean对象的factory-method方法创建bean.

• Dependency injection

  
  

1.Constructor-based dependency injection

<bean id = "people" class = "com.jiakai.spring.People"><constructor-arg name="name" value="jiakai"/><constructor-arg name="age" value="22"/></bean>

package com.jiakai.spring;public class People {private String name;private int age;public People(String name,int age) {System.out.println("make people");this.name = name;this.age = age;}@Overridepublic String toString() {return name+" "+age;}}

利用构造函数注入

2.Setter-based dependency injection

<bean id = "people" class = "com.jiakai.spring.People"><property name="name" value="gaoshang" /><property name="age" value="25" /></bean>

package com.jiakai.spring;public class People {private String name;private int age;public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {return name+" "+age;}}

利用setter方法注入

3.Collections

<bean id="moreComplexObject" class="example.ComplexObject"><!-- results in a setAdminEmails(java.util.Properties) call --><property name="adminEmails">  <props>      <prop key="administrator">[e-mail]</prop>      <prop key="support">[e-mail]</prop>      <prop key="development">[e-mail]</prop>  </props></property><!-- results in a setSomeList(java.util.List) call --><property name="someList">  <list>      <value>a list element followed by a reference</value>      <ref bean="myDataSource" />  </list></property><!-- results in a setSomeMap(java.util.Map) call --><property name="someMap">  <map>      <entry key="an entry" value="just some string"/>      <entry key ="a ref" value-ref="myDataSource"/>  </map></property><!-- results in a setSomeSet(java.util.Set) call --><property name="someSet">  <set>      <value>just some string</value>      <ref bean="myDataSource" />  </set></property></bean>

4.Null and empty string values

<bean class="ExampleBean"><property name="email" value=""/></bean><bean class="ExampleBean"><property name="email"><null/></property></bean>

5.Lazy-initialized beans

<bean id = "car" class = "com.jiakai.spring.Car" lazy-init="true"/>

<beans default-lazy-init="true"><!-- no beans will be pre-instantiated... --></beans>

懒初始化

6.Autowiring collaborators

no: 不进行自动装配

byType:根据类型进行自动装配,如果匹配类型时,有多个匹配结果,则抛异常.

byName:根据名字进行自动装配,如果找不到名字相同的bean时,则抛异常.

• Bean scopes

  
  

1.singleton:只有一个

2.prototype:每次都新建一个

• Customizing the nature of a bean

  
  

<bean id="exampleInitBean" class="examples.ExampleBean" init-method="init"/><bean id="exampleInitBean" class="examples.ExampleBean" destroy-method="cleanup"/>

• Annotation-based container configuration

  
  

<context:annotation-config/>

对Spring进行Annotation配置的时候,首先要在beans.xml里面加上上面那句话。

相当于,加载了一些类扫描器,这样Spring在初始化容器的时候,一边初始化bean一边扫描Annotation,辅助初始化bean.

1.@Required

标识该属性为对象必需的属性,如果构造该bean的时候,没有注入该属性,则抛异常。

相当于检查某属性,是否被注入过。

2.@Autowired

为对象注入属性，默认按类型装配,也可以与@Qualifier配合使用.

另外@Autowired中有一个required属性,默认为true.

<bean id = "people" class = "com.jiakai.spring.People"/><bean id = "ttcar" class = "com.jiakai.spring.Car"><qualifier value="cc"/></bean><bean id = "ttcar1" class = "com.jiakai.spring.Car"></bean>

package com.jiakai.spring;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.beans.factory.annotation.Required;public class People {private String name;private int age;private Car car;public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}public void drive(){this.car.run();}@Autowired@Qualifier(value="cc")public void setCar(Car car) {this.car = car;}@Overridepublic String toString() {return name+" "+age;}}

3.@Resource

为对象注入属性,默认按照名称装配,当找不到与名称匹配的bean才会按照类型装配.

可以通过name属性指定,如果没有指定name属性,则按照属性名匹配.

<bean id = "people" class = "com.jiakai.spring.People"/><bean id = "car" class = "com.jiakai.spring.Car"/>

package com.jiakai.spring;import javax.annotation.Resource;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.beans.factory.annotation.Required;public class People {private String name;private int age;private Car car;public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}public void drive(){this.car.run();}@Resourcepublic void setCar(Car car) {this.car = car;}@Overridepublic String toString() {return name+" "+age;}}

4.@PostConstruct  & @PreDestroy

@PostConstruct:在对象创建之后,调用该方法.

@PreDestroy:在对象销毁之前,调用该方法.

<bean id = "car" class = "com.jiakai.spring.Car"/>

package com.jiakai.spring;import javax.annotation.PostConstruct;import javax.annotation.PreDestroy;public class Car {private String name;public Car(){System.out.println("make car with default");}public void run(){System.out.println(name+" car run on the road");}public String getName() {return name;}public void setName(String name) {this.name = name;}@PostConstructpublic void init(){System.out.println("init");}@PreDestroypublic void destroy(){System.out.println("destroy");}}

5.@Component

相当于Spring会生成该类的一个对象,作为自己的组件bean进行管理.

该注解需要与下面的配置配合使用.

<context:component-scan base-package="com.jiakai"/>

设置需要扫描Component的包.