学步园

本文javaeye同步更新地址：

http://lcllcl987.javaeye.com/blog/351655

spring2以上版本支持自定义标签.
作为一般的应用程序开发人员，扩展spring的标签意义不大。

但如果你是一个平台开发人员，则很有必要拥有一套自己的标签, 提供给应用开发人员使用.
由于mule的标签是基于spring的xml schema扩展的, 为了弄出mule的自定义标签， 今天研究了一下spring的标签扩展, 并笔记之
让我们从一个简单的spring标签制作开始吧。
我需要做的标签如下：
<co:log id="iplatformLog" isPrintTime="true" company="cyber" />
这个标签功能简单， 仅仅打印一下log.它和如下spring bean功能一样：
<bean id="log" class="co.iplatform.log.LogBean"><br /> <constructor-arg value="true"></constructor-arg><br /> <property name="company" value="cyber"></property><br /> </bean>

标签的schema如下：
<?xml version="1.0" encoding="UTF-8"?><br /> <xsd:schema xmlns="http://www.springframework.org/schema/myns"<br /> xmlns:xsd="http://www.w3.org/2001/XMLSchema"<br /> xmlns:beans="http://www.springframework.org/schema/beans"<br /> targetNamespace="http://www.mycompany.com/schema/myns"<br /> elementFormDefault="qualified"<br /> attributeFormDefault="unqualified"><br /> <xsd:import namespace="http://www.springframework.org/schema/beans"/></p> <p> <xsd:element name="log"><br /> <xsd:complexType><br /> <xsd:complexContent><br /> <xsd:extension base="beans:identifiedType"><br /> <xsd:attribute name="isPrintTime" type="xsd:boolean" use="required"/><br /> <xsd:attribute name="company" type="xsd:string"/><br /> </xsd:extension><br /> </xsd:complexContent><br /> </xsd:complexType><br /> </xsd:element><br /> </xsd:schema>

log标签背后的bean如下：
public class LogBean<br /> {<br /> private boolean isPrintTiem = false;</p> <p> private String company = "";</p> <p> public LogBean(boolean isPrintTime)<br /> {<br /> this.isPrintTiem = isPrintTime;<br /> }</p> <p> public void print(String log)<br /> {<br /> if(this.isPrintTiem)<br /> System.out.println(this.company + new Date() + ":" + log);<br /> else<br /> System.out.println(this.company + ":" + log);<br /> }<br /> public String getCompany()<br /> {<br /> return company;<br /> }<br /> public void setCompany(String company)<br /> {<br /> this.company = company;<br /> }<br /> public boolean isPrintTiem()<br /> {<br /> return isPrintTiem;<br /> }<br /> }

实现一个标签需要扩展一个class：
NamespaceHandlerSupport

并实现一个interface：

BeanDefinitionParser<br /> public class LogNamespaceHandler extends NamespaceHandlerSupport<br /> {</p> <p> public void init()<br /> {<br /> registerBeanDefinitionParser("log",<br /> new LogBeanDefinitionParser());<br /> }<br /> }<br />
LogNamespaceHandler在spring的Ioc容器加载配置文件时，遇到log节点便会调用LogBeanDefinitionParser，完成bean的初始化，并注册到spring context中.
public class LogBeanDefinitionParser implements<br /> BeanDefinitionParser {<br /> public BeanDefinition parse(Element element, ParserContext parserContext) {<br /> // create a RootBeanDefinition that will serve as configuration<br /> // holder for the 'pattern' attribute and the 'lenient' attribute<br /> RootBeanDefinition beanDef = new RootBeanDefinition();<br /> beanDef.setBeanClass(LogBean.class);<br /> // never null since the schema requires it<br /> String pattern = element.getAttribute("isPrintTime");<br /> beanDef.getConstructorArgumentValues().addGenericArgumentValue(pattern);<br /> String company = element.getAttribute("company");<br /> if(StringUtils.hasText(company))<br /> {<br /> beanDef.getPropertyValues().addPropertyValue("company",company);<br /> }<br /> // retrieve the ID attribute that will serve as the bean identifier in<br /> // the context<br /> String id = element.getAttribute("id");<br /> // create a bean definition holder to be able to register the<br /> // bean definition with the bean definition registry<br /> // (obtained through the ParserContext)<br /> BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDef, id);<br /> // register the BeanDefinitionHolder (which contains the bean<br /> // definition)<br /> // with the BeanDefinitionRegistry<br /> BeanDefinitionReaderUtils.registerBeanDefinition(holder, parserContext<br /> .getRegistry());<br /> return beanDef;<br /> }<br /> }<br />
最后在META_INF中， 加入两个配置文件：
spring.handlers和spring.schemas
spring.handlers内容如下：
http/://www.mycompany.com/schema/myns=co.iplatform.log.LogNamespaceHandler<br /> spring.schemas内容如下：<br /> http/://www.mycompany.com/schema/myns/myns.xsd=co/iplatform/log/logns.xsd

最后测试一下：
新建一个applicationContext.xml：
<?xml version="1.0" encoding="UTF-8"?><br /> <beans xmlns="http://www.springframework.org/schema/beans"<br /> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"<br /> xmlns:co="http://www.mycompany.com/schema/myns"<br /> xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd<br /> http://www.mycompany.com/schema/myns http://www.mycompany.com/schema/myns/myns.xsd<br /> "><br /> <co:log id="iplatformLog" isPrintTime="true" company="cyberObject" /></p> <p> <bean id="log" class="co.iplatform.log.LogBean"><br /> <constructor-arg value="true"></constructor-arg><br /> <property name="company" value="cyberObject"></property><br /> </bean><br /> </beans>

testcase：
public class LogTagTest extends AbstractDependencyInjectionSpringContextTests<br /> {<br /> protected String[] getConfigLocations()<br /> {<br /> return new String[] {"classpath*:applicationContext*.xml"};<br /> }</p> <p> public void testLogBean()<br /> {<br /> LogBean logBean = (LogBean)this.applicationContext.getBean("iplatformLog");<br /> assertTrue(StringUtils.hasText(logBean.getCompany()));<br /> assertTrue(logBean.isPrintTiem());<br /> logBean.print("is fun!");</p> <p> }<br /> }

绿色在期待中出现.

为了让mule使用这个bean， 只需mule的配置文件导入上面的spring的Application.xml

<br /> <spring:beans><br /> <spring:import resource="applicationContext.xml" /><br /> </spring:beans>

然后定义一个mule：
<model name="LogModel"><br /> <service name="databaseCommonUMO"><br /> <!-- any number of endpoints can be added to an inbound router --><br /> <inbound><br /> <vm:inbound-endpoint path="logQueue" /><br /> </inbound><br /> <component><br /> <method-entry-point-resolver><br /> <include-entry-point method="print" /><br /> </method-entry-point-resolver><br /> <spring-object bean="iplatformLog"></spring-object><br /> </component><br /> </service><br /> </model><br /> </mule>

写一个mule的测试：
public class MySpringTagMuleClientTest<br /> {<br /> public static void main(String[] args) throws MuleException<br /> {<br /> // create mule<br /> MuleContext muleContext;<br /> String config = "mule-myspringtag-config.xml";<br /> muleContext = new DefaultMuleContextFactory().createMuleContext(config);<br /> muleContext.start();<br /> // creat mule client<br /> MuleClient client = new MuleClient();<br /> MuleMessage response = client.send("vm://logQueue", "hello, I'm log content.", null);<br /> }<br /> }