Spring_自定义标签的使用

写在前面：

你们下载spring源码的话再test项目中会有一个示例Demo.这里我是仿照demo,写的一个简单的例子，事实上官网给的demo写的更为复杂，是对象里面包含List变量的.同时参考了《Spring源码深度解析》一书第4章内容，在此声明。

    1.定义一个普通的POJO,也就是未来咱们要在spring配置文件里面要注入的bean

/**
 * 
 * @author zhouplus
 * @since 5.0
 */
public class User {
	private String name;
	private String age;

    //getter and setter

}

    2.定义一个XSD文件描述组件内容

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<xsd:schema xmlns="http://www.zhou.com/schema/user"
         xmlns:xsd="http://www.w3.org/2001/XMLSchema"
         targetNamespace="http://www.zhou.com/schema/user"
         elementFormDefault="qualified"
         attributeFormDefault="unqualified">

   <xsd:element name="user">
      <xsd:complexType>
         <xsd:attribute name="id" type="xsd:ID"/>
         <xsd:attribute name="name" use="required" type="xsd:string"/>
         <xsd:attribute name="age" use="required" type="xsd:string"/>
      </xsd:complexType>
   </xsd:element>

</xsd:schema>

 

3.建立一个文件，实现BeanDefinitionParser接口，这里继承自AbstractBeanDefinitionParser

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.zhou;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractBeanDefinitionParser;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;

/**
 * 
 * @author zhouplus
 * @since 5.0
 */
public class UserBeanDefinitionParser extends AbstractBeanDefinitionParser {

	/* (non-Javadoc)
	 * @see org.springframework.beans.factory.xml.AbstractBeanDefinitionParser#parseInternal(org.w3c.dom.Element, org.springframework.beans.factory.xml.ParserContext)
	 */
	@Override
	protected AbstractBeanDefinition parseInternal(Element element,
			ParserContext parserContext) {
		return parseUserElement(element);
	}
	
	private static AbstractBeanDefinition parseUserElement(Element element) {
		BeanDefinitionBuilder factory = BeanDefinitionBuilder.rootBeanDefinition(UserFactoryBean.class);
		factory.addPropertyValue("user", parseUser(element));
		return factory.getBeanDefinition();
	}
	
	private static BeanDefinition parseUser(Element element) {
		BeanDefinitionBuilder component = BeanDefinitionBuilder.rootBeanDefinition(User.class);
		component.addPropertyValue("name", element.getAttribute("name"));
		component.addPropertyValue("age", element.getAttribute("age"));
		return component.getBeanDefinition();
	}
	
}

 

4.建立一个Handler文件，扩展自NamespaceHandlerSupport，目的是将组件注册到spring容器

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.zhou;

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;


/**
 * 
 * @author zhouplus
 * @since 5.0
 */
public class MyNamespaceHandler extends NamespaceHandlerSupport {

	/* (non-Javadoc)
	 * @see org.springframework.beans.factory.xml.NamespaceHandler#init()
	 */
	@Override
	public void init() {
		registerBeanDefinitionParser("user", new UserBeanDefinitionParser());
	}

}

 

5.编写Spring.handlers 和Spring.schemes文件，默认位置是在工程的/META-INF/文件夹下，固然，你能够经过Spring的扩展或者修改源码的方式修改路径。

Spring.handlers内容：

http\://www.zhou.com/schema/user=com.zhou.MyNamespaceHandler

Spring.schemes内容：

http\://www.zhou.com/schema/user/user.xsd=com/zhou/user.xsd

6.建立配置文件user-config.xml在配置文件中引入对应的命名空间以及XSD后，即可以直接使用自定义标签了。

<?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:zhou="http://www.zhou.com/schema/user"
      xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.zhou.com/schema/user http://www.zhou.com/schema/user/user.xsd">

   <zhou:user id="testbean" name="zhangsan" age="18" />

</beans>

7.测试，这里简单使用main方法测试，写更多测试的话建议使用Junit单元测试。

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.zhou;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * 
 * @author zhouplus
 * @since 5.0
 */
public class MyMain {
	public static void main(String[] args) {
		System.out.println("进入main");
		ApplicationContext bf = new ClassPathXmlApplicationContext("com/zhou/user-config.xml");
		System.out.println("Application初始化完成");
		User user =  (User) bf.getBean("testbean");
		System.out.println(user.getName() + "," + user.getAge());
	}
}

8.测试结果

 

结语：

上面的例子中，咱们实现了经过自定义标签实现了经过了属性的方式将user类型的Bean赋值，在Spring中自定义标签分厂经常使用，例如咱们熟知的事物标签：tx(<tx:annotation-driven>)

看到这里是否想倒能够把你本身写的组件和spring无缝集成？