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JSF In Action 学习之二 [原创](Managed Bean的创建与初始化)

Managed Bean的创建与初始化

1Managed Bean 被定义在faces-config.xml里,当这个Bean第一次被引用时就会被初始化,

它的生存周期由<managed-bean-scope>XXX</managed-bean-scope>来决定,

<managed-bean>

<managed-bean-name>user</managed-bean-name>

<managed-bean-class>org.examples.TestBean</managed-bean-class>

<managed-bean-scope>session</managed-bean-scope>

<managed-property>

<property-name>id</property-name>

<value>111</value>

</managed-property>

<managed-property>

<property-name>name</property-name>

<value>gembin</value>

</managed-property>

</managed-bean>

 

这里其实用了反转控制(Inversion of Control, IoC) type 2, 即通过Setter注入,具体可参考Fowler, Dependency Injection这本书。假如你需要当Application Startup的时候就要初始化一些Bean(例如建立数据库连接,因为它的初始化需要1段时间),这就需要加ServletContextListener

 

2.声明Lists and Maps作为managed beans

 

这里managed-bean-class必须是个实现类,而不能是List 或者Map,因为他们是接口,不能被初始化.

并且用<list-entries><map-entry>代替<managed-property>

 

<managed-bean>

<description>List of favorite sites</description>

<managed-bean-name>favoriteSites</managed-bean-name>

<managed-bean-class>java.util.ArrayList</managed-bean-class>

<managed-bean-scope>application</managed-bean-scope>

<list-entries>

<value>http://www.jsfcentral.com</value>

<value>http://www.theserverside.com</value>

<value>http://www.ibm.com/developerworks/</value>

<value>http://otn.oracle.com</value>

<value>http://www.java.net</value>

<value>http://www.manning.com</value>

</list-entries>

</managed-bean>

 

<managed-bean>

<description>List of favorite sites, keyed by name.</description>

<managed-bean-name>favoriteSitesMap</managed-bean-name>

<managed-bean-class>java.util.HashMap</managed-bean-class>

<managed-bean-scope>application</managed-bean-scope>

<map-entries>

<map-entry>

<key>JSF Central</key>

<value>http://www.jsfcentral.com</value>

</map-entry>

<map-entry>

<key>TheServerSide.com</key>

<value>http://www.theserverside.com</value>

</map-entry>

<map-entry>

<key>IBM DeveloperWorks</key>

<value>http://www.ibm.com/developerworks/</value>

</map-entry>

<map-entry>

<key>Oracle Technology Network</key>

<value>http://otn.oracle.com</value>

</map-entry>

<map-entry>

<key>java.net</key>

<value>http://www.java.net</value>

</map-entry>

<map-entry>

<key>Manning Publications</key>

<value>http://www.manning.com</value>

</map-entry>

</map-entries>

</managed-bean>

 

 

3. value-binding expressions引用managed beans

假如有如下Beans

<managed-bean>

<description>test</description>

<managed-bean-name>user</managed-bean-name>

<managed-bean-class>org.examples.UserBean</managed-bean-class>

<managed-bean-scope>session</managed-bean-scope>

</managed-bean>

 

<managed-bean>

<managed-bean-name>referer </managed-bean-name>

<managed-bean-class>org.examples.Referer</managed-bean-class>

<managed-bean-scope>request</managed-bean-scope>

<managed-property>

<property-name>user</property-name>

<value>#{user}</value>

</managed-property>

</managed-bean>

 

这里referervalue-binding expressions引用了user,但是引用是不能循环的,即user不能在反过来引用referer,由此可见用value-binding expressions是相当的灵活阿,哈哈

 To be continued....

posted on 2008-03-05 12:19 gembin 阅读(2022) 评论(0)  编辑  收藏 所属分类: JSF


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