Spring 管理bean的生命周期

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两个生命周期时间与bean关系尤为重要：
postinitialization（初始化后）和predestruction（销毁前）。

（Spring并不管理那些被配置成非单例bean的生命周期）

指定初始化方法：

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package cn.partner4java.init;  
  
/** 
* 指定初始化方法 
* @author partner4java 
* 
*/  
public class SimpleBean {  
    private String name;  
    private int age = 0;  
      
    public void init(){  
        if(name == null){  
            System.out.println("name为空");  
        }  
        if(age == 0){  
            System.out.println("age为0");  
        }  
    }  
      
    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;  
    }  
      
}  

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<?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="simple1" class="cn.partner4java.init.SimpleBean"  
            init-method="init">  
        <property name="age" value="29"/>  
        <property name="name" value="Dr. Jekyll"/>  
    </bean>  
    <bean id="simple2" class="cn.partner4java.init.SimpleBean"  
            init-method="init">  
        <property name="age" value="29"/>  
    </bean>  
    <bean id="simple3" class="cn.partner4java.init.SimpleBean"  
            init-method="init">  
        <property name="name" value="Mr. Hyde"/>  
    </bean>  
  
</beans>  

调用：

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        //在调用获取的时候就会调用init，在调用init之前，已经使用控制反转设置方法依赖注入设置进数据  
        BeanFactory beanFactory = getBeanFactory();  
        System.out.println("simple1");  
        beanFactory.getBean("simple1");  
        System.out.println("simple2");  
        beanFactory.getBean("simple2");  
        System.out.println("simple3");  
        beanFactory.getBean("simple3");  
          
//      后台打印：  
//      simple1  
//      simple2  
//      name为空  
//      simple3  
//      age为0  

实现InitializingBean接口：
Spring中InitializingBean接口允许你在bean的代码中这样定义：你希望bean能接收到Spring已经完成对其配置的通知。就像使用初始化方法时一样，你可以借机检查bean的配置以确保其有效，若要必要，还可以给出默认值。

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public class SimpleBeanIB implements InitializingBean {  
    private static final String DEFAULT_NAME = "Jan Machacek";  
    private String name;  
    private int age = 0;  
  
    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;  
    }  
  
    @Override  
    public String toString() {  
        final StringBuilder sb = new StringBuilder();  
        sb.append("SimpleBean");  
        sb.append("{name='").append(name).append('\'');  
        sb.append(", age=").append(age);  
        sb.append('}');  
        return sb.toString();  
    }  
  
    public void afterPropertiesSet() throws Exception {  
        System.out.println("initializing bean");  
        if (this.name == null) {  
            System.out.println("No name specified, using default.");  
            this.name = DEFAULT_NAME;  
        }  
        if (this.age == 0) {  
            throw new IllegalArgumentException("You must set the [age] property bean of type [" + getClass().getName() + "]");  
        }  
    }  
}  

决议顺序：
Spring首先调用InitializingBean.afterPropertiesSet()方法，然后再调用初始化方法。（建议如果存在顺序，都写入到afterPropertiesSet中调用。）

afterPropertiesSet方法和类的继承：
例子抽象父类实现了接口，但是把afterPropertiesSet定义成了final，不可被子类覆盖，也就是去实现一些通用的初始化，然后再调用了自己定义的initSimple()初始化方法。
父类：

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public abstract class SimpleBeanSupport implements InitializingBean {  
    private String value;  
  
    /** 
     * Subclasses may override this method to perform additional initialization. 
     * This method gets invoked after the initialization of the {@link SimpleBeanSupport} 
     * completes. 
     * @throws Exception If the subclass initialization fails. 
     */  
    protected void initSimple() throws Exception {  
        // do nothing  
    }  
  
    public final void afterPropertiesSet() throws Exception {  
        Assert.notNull(this.value, "The [value] property of [" + getClass().getName() + "] must be set.");  
        initSimple();  
    }  
  
    public final void setValue(String value) {  
        this.value = value;  
    }  
  
    protected final String getValue() {  
        return this.value;  
    }  
}  

继承：

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public class SoutSimpleBean extends SimpleBeanSupport {  
    private String person;  
  
    protected void initSimple() throws Exception {  
        Assert.notNull(this.person, "The [person] property of [" + getClass().getName() + "] must be set.");  
    }  
  
    public void setPerson(String person) {  
        this.person = person;  
    }  
  
    @Override  
    public String toString() {  
        return String.format("%s says \"%s\"", this.person, getValue());  
    }  
}  

配置文件：

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<?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="simple1" class="com.apress.prospring2.ch04.lifecycle.SoutSimpleBean">  
        <property name="person" value="Winston Churchill"/>  
        <property name="value" value="This report, by its very length, defends itself against the risk of being read."/>  
    </bean>  
  
</beans>  

嵌入bean的销毁：
1、bean销毁时执行某一方法

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public class DestructiveBean implements InitializingBean {  
    private InputStream is = null;  
    private String filePath = null;  
  
    public void afterPropertiesSet() throws Exception {  
        System.out.println("Initializing Bean");  
  
        Assert.notNull(this.filePath, "The [filePath] property of [" + getClass().getName() + "] must be set.");  
  
        new File(this.filePath).createNewFile();  
        this.is = new FileInputStream(this.filePath);  
    }  
  
    public void destroy() {  
        System.out.println("Destroying Bean");  
  
        if (this.is != null) {  
            try {  
                this.is.close();  
                this.is = null;  
                new File(this.filePath).delete();  
            } catch (IOException ex) {  
                System.err.println("WARN: An IOException occured"  
                        + " while trying to close the InputStream");  
            }  
        }  
    }  
  
    public void setFilePath(String filePath) {  
        this.filePath = filePath;  
    }  
  
    @Override  
    public String toString() {  
        final StringBuilder sb = new StringBuilder();  
        sb.append("DestructiveBean");  
        sb.append("{is=").append(is);  
        sb.append(", filePath='").append(filePath).append('\'');  
        sb.append('}');  
        return sb.toString();  
    }  
}  

配置文件：

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<?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="destructive" class="com.apress.prospring2.ch04.lifecycle.DestructiveBean"  
            destroy-method="destroy">  
        <property name="filePath" value="/tmp/prospring25"/>  
    </bean>  
  
</beans>  

2、实现DisposableBean接口
DisposableBean接口提供了destory方法。

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public class DestructiveBeanI implements InitializingBean, DisposableBean {  
    private InputStream is = null;  
    private String filePath = null;  
  
    public void afterPropertiesSet() throws Exception {  
        System.out.println("Initializing Bean");  
  
        Assert.notNull(this.filePath, "The [filePath] property of [" + getClass().getName() + "] must be set.");  
  
        new File(this.filePath).createNewFile();  
        this.is = new FileInputStream(this.filePath);  
    }  
  
    public void destroy() {  
        System.out.println("Destroying Bean");  
  
        if (this.is != null) {  
            try {  
                this.is.close();  
                this.is = null;  
                new File(this.filePath).delete();  
            } catch (IOException ex) {  
                System.err.println("WARN: An IOException occured"  
                        + " while trying to close the InputStream");  
            }  
        }  
    }  
  
    public void setFilePath(String filePath) {  
        this.filePath = filePath;  
    }  
  
    @Override  
    public String toString() {  
        final StringBuilder sb = new StringBuilder();  
        sb.append("DestructiveBean");  
        sb.append("{is=").append(is);  
        sb.append(", filePath='").append(filePath).append('\'');  
        sb.append('}');  
        return sb.toString();  
    }  
}  

配置文件：

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<?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="destructive" class="com.apress.prospring2.ch04.lifecycle.DestructiveBeanI">  
        <property name="filePath" value="/tmp/prospring25"/>  
    </bean>  
  
</beans>  

3、使用关闭钩子
注入关闭代码：

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public class ShutdownHook implements Runnable {  
    private ConfigurableListableBeanFactory beanFactory;  
  
    public ShutdownHook(ConfigurableListableBeanFactory beanFactory) {  
        Assert.notNull(beanFactory, "The 'beanFactory' argument must not be null.");  
        this.beanFactory = beanFactory;  
    }  
  
    public void run() {  
        this.beanFactory.destroySingletons();  
    }  
}  

调用代码：

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public class ShutdownHookDemo {  
  
    public static void main(String[] args) throws IOException {  
        XmlBeanFactory factory = new XmlBeanFactory(new ClassPathResource("/META-INF/spring/lifecycledemo5-context.xml"));  
        Runtime.getRuntime().addShutdownHook(new Thread(new ShutdownHook(factory)));  
        new BufferedInputStream(System.in).read();  
    }  
  
}  