spring自定义标签实现

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Spring中，除了使用官方提供的bean等标签外，也提供了方便开发者自定义标签的实现方式，废话少续，直接上步骤：

创建schema文件(myns.xsd):

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

创建命名空间处理类(MyNameSpaceHandler.java)：

package spring.extensibletag;import org.springframework.beans.factory.xml.NamespaceHandlerSupport;public class MyNameSpaceHandler extends NamespaceHandlerSupport {@Overridepublic void init() {registerBeanDefinitionParser("dateformat", new SimpleDateFormatBeanDefinitionParser());}}

创建自定义bean的parser类：

package spring.extensibletag;import java.text.SimpleDateFormat;import org.springframework.beans.factory.support.BeanDefinitionBuilder;import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;import org.springframework.util.StringUtils;import org.w3c.dom.Element;public class SimpleDateFormatBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {@Overrideprotected Class<?> getBeanClass(Element element) {return SimpleDateFormat.class;}@Overrideprotected void doParse(Element element, BeanDefinitionBuilder bean) {// this will never be null since the schema explicitly requires that a value be supplied          String pattern = element.getAttribute("pattern");          bean.addConstructorArg(pattern);            // this however is an optional property          String lenient = element.getAttribute("lenient");          if (StringUtils.hasText(lenient)) {              bean.addPropertyValue("lenient", Boolean.valueOf(lenient));          }  }}

注册处理类和命名空间定义schema文件(spring.handlers和spring.schemas)：

spring.handlershttp\://www.mycompany.com/schema/myns=spring.extensibletag.MyNameSpaceHandler

spring.schemashttp\://www.mycompany.com/schema/myns/myns.xsd=myns.xsd

在spring的applicationContext.xml文件中定义bean：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:myns="http://www.mycompany.com/schema/myns"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd          http://www.mycompany.com/schema/myns         http://www.mycompany.com/schema/myns/myns.xsd"><myns:dateformat id="defaultDateFormat" pattern="yyyy-MM-dd HH:mm" lenient="true" /></beans>

使用示例：

package spring.extensibletag;import java.text.SimpleDateFormat;import java.util.Date;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class Test {@SuppressWarnings("resource")public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");SimpleDateFormat format = (SimpleDateFormat) context.getBean("defaultDateFormat");System.out.println(format.format(new Date()));}}

该示例所在项目的文件目录如下图所示：

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