spring in action 2.0读书笔记(3)

spring in action 2.0读书笔记(三)

<bean id="baseSaxophonist" class="com.springinaction.springidol.Instrumentalist"
abstract="true">
<property name="instrument" ref="saxophone" />
<property name="song" value="Jingle Bells" />
</bean>
<bean id="kenny" parent="baseSaxophonist" />
<bean id="david" parent="baseSaxophonist" />

Spring inheritance(different from Java inheritance)： abstract and parent, is commonly used to reduce the amount of redundant XML. e.g: TransactionProxyFactoryBean.

Spring提供了method injection功能，使你能够在runtime期间把method注入到class里.Spring提供了2种方式的method injection：
1．Method replacement—Enables existing methods (abstract or concrete) to be replaced at runtime with new implementations.

<bean id="magicBox"
    class="com.springinaction.springidol.MagicBoxImpl">
        <replaced-method name="getContents" replacer="tigerReplacer" />
</bean> 
<bean id="tigerReplacer" class="com.springinaction.springidol.TigerReplacer" />
 
import org.springframework.beans.factory.support.MethodReplacer;
public class TigerReplacer implements MethodReplacer {
    public Object reimplement(Object target, Method method,
        Object[] args) throws Throwable {
            return "A ferocious tiger";
    }
}

2．Getter injection—Enables existing methods (abstract or concrete) to be replaced at runtime with a new implementation that returns a specific bean from the Spring context. （这种方式是for"使用get开头的，而且返回值是在spring里有bean定义类型"的方法）

<bean id="stevie"
    class="com.springinaction.springidol.Instrumentalist">
        <lookup-method name="getInstrument" bean="guitar" />
</bean>

There’s no need to write a MethodReplacer class.

Injecting non-Spring beans
对于在spring里有定义bean，但又不是通过spring来创建的class，又应该如何使用spring呢？这种情况是可能的：例如，一个由ORM创建的object则不是spring创建的。
第一步：把bean定义成abstract:

<bean id="pianist"
    class="com.springinaction.springidol.Instrumentalist"
         abstract="true">
        <property name="instrument">
            <bean class="com.springinaction.springidol.Piano" />
        </property>
</bean>

第二步：如果把上面的定义（注意上面设置的id）和class联系起来

@Configurable("pianist")
public class Instrumentalist implements Performer {
…
}

@Configurable的作用有2个：
1> 它表明Instrumentalist的实例会被纳入和配置到spring container里，即使它是在outside of spring创建。
2> 它把Instrumentalist class与id为pianist联系在一起，当spring在配置一个实例时，它会寻找pianist bean作为模板来进行配置（包括DI）
第三步：在spring configure file里添加下列代码

<aop:spring-configured />

它表示有一些在外部创建的beans，需要被配置和纳入进spring container.
请注意：<aop:spring-configured/>是用到aspectJ，这意味着你的APP必须在一个AspectJ-enabled JVM里运行。
The best way to AspectJ-enable a Java 5 JVM is to start it with the following JVM argument:
-javaagent:/path/to/aspectjweaver.jar

Registering custom property editors
extends java.beans.PropertyEditorSupport

public class PhoneEditor
    extends java.beans.PropertyEditorSupport {
    //text value example “111-111-111”
    public void setAsText(String textValue) {
       String areaCode = textValue.substring(0,3);
       String prefix = textValue.substring(4,7);
       String number = textValue.substring(8);
       PhoneNumber phone = new PhoneNumber(areaCode, prefix, number);
       setValue(phone);
    }
}
<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
    <property name="customEditors">
       <map>
           <entry key="com.springinaction.chapter03.propeditor.PhoneNumber">
              <bean id="phoneEditor" class="com.springinaction.chapter03.propeditor.PhoneEditor">
              </bean>
           </entry>
       </map>
    </property>
</bean>

CustomEditorConfigurer实质上是一个BeanFactoryPostProcessor，因此它会在bean factory初始化之后调用registerCustomEditor()方法来把custom editors load进BeanFactory里。
Postprocessing beans
PostProcessor有2种：
1） Bean PostProcessor (注意：BeanPostProcessor是for all beans的，not for one bean)implements BeanPostProcessor
postProcessBeforeInitialization()方法是在bean初始化之前被调用（即在bean定义中设置的“init-method”方法执行之前或实现InitializingBean接口的Bean的afterPropertiesSet()方法执行之前）
postProcessAfterInitialization()方法是在初始化之后被调用（即在bean定义中设置的“init-method”方法执行之后或实现InitializingBean接口的Bean的afterPropertiesSet()方法执行之后）
2） Bean Factory PostProcessor implements BeanFactoryPostProcessor
postProcessBeanFactory()方法会在all beans loaded之后，任何bean（包括BeanPostProcessor beans）被初始化（instantiated）之前，被spring container所调用。
Externalizing configuration properties

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
       <property name="location" value="jdbc.properties" />
</bean>
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="url" value="${database.url}" />
    <property name="driverClassName" value="${database.driver}" />
    <property name="username" value="${database.user}" />
    <property name="password" value="${database.password}" />
</bean>

Resolving resource messages

<bean id="messageSource"
class="org.springframework.context.support.ResourceBundleMessageSource">
    <property name="basename">
       <value>trainingtext</value>
    </property>
</bean>
<spring:message code="computer"/>

Spring提供了一些Aware接口，如BeanFactoryAware、ApplicationContextAware、ResourceLoaderAware、ServletContextAware等等。比如，实现了BeanFactoryAware接口的bean，Spring容器会自动把BeanFactory对象注入该bean（当然，前提是该bean有一个BeanFactory变量），而实现了ApplicationContextAware接口的bean，会自动把ApplicationContext对象注入该bean（当然，前提是该bean有一个ApplicationContext变量）
Decoupling with application events
第一步：定义一个application event，它扩展了ApplicationEvent抽象类
第二步：定义一个Application listener，它实现org.springframework.context.ApplicationListener接口。

class HeartbeatForwarder implements ApplicationListener {
　public void onApplicationEvent(ApplicationEvent event) {
　　if (event instanceof HeartbeatEvent) {
　　　System.out.println("Received heartbeat event: " + event.getTimestamp());
　　}
　}
}

第三步：在spring里注册该listener。
第四步: 用来publish event的bean,因为publish event需要用到applicationcontext,所以implements ApplicationContextAware

class HeartbeatTask extends TimerTask implements ApplicationEventPublisherAware {

　private ApplicationEventPublisher eventPublisher;

　public void run() {
　　HeartbeatEvent event = new HeartbeatEvent(this);
　　eventPublisher.publishEvent(event);
　}

　public void setApplicationEventPublisher(ApplicationEventPublisher eventPublisher) {
　　this.eventPublisher = eventPublisher;
　}
}

Scripting beans
把script bean注入到java class bean

<lang:jruby id="lime"
    script-source="classpath:com/springinaction/scripting/Lime.rb"
    script-interfaces="com.springinaction.scripting.Lime" />

把java class bean注入到script bean

<lang:groovy id="coconut"
script-source="classpath:com/springinaction/scripting/Coconut.groovy">
       <lang:property name="lime" ref="lime" />
</lang:groovy>

Refreshing scripted beans

<lang:jruby id="lime"
script-source="classpath:com/springinaction/scripting/Lime.rb"
script-interfaces="com.springinaction.scripting.Lime"
refresh-check-delay="5000"/>

Writing scripted beans inline

<lang:bsh id="lime"
    script-interfaces="com.springinaction.scripting.Lime">
<lang:inline-script><![CDATA[
void drink() {
System.out.println("Called the doctor woke him up!");
}
]]>
</lang:inline-script>
</lang:bsh>