自定义Spring标签

写了好几次了，结果一段时间之后就忘记了自己有写好的example，但是最后还是决定重新写一遍，把这个步骤记录下来

首先看整个项目结构

从transaction.xml开始，虽然图上报错了，实际上运行并没有问题，IDE功能的不完善吧。

其中声明了sb命名空间，并且schemaLocation中写明了schema地址是http://www.springbank.com/schema/springbank.xsd

<?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:context="http://www.springframework.org/schema/context"

    xmlns:sb="http://www.springbank.com/schema/springbank"

    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd

                        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd

                        http://www.springbank.com/schema/springbank http://www.springbank.com/schema/springbank.xsd

                        ">

    <!-- 交易处理器扫描并实例化 -->

    <context:component-scan base-package="com.springbank.portal.controller"/>

    <sb:transaction id="testTransaction" action="testAction" template="noTemplate"></sb:transaction>

</beans>

显然不会真的去http://www.springbank.com/schema/springbank.xsd寻找xsd，spring实际上是从spring.schemas文件里去寻找真正的地址，我这个example项目中，spring.schemas文件只有一行：

http\://www.springbank.com/schema/springbank.xsd=META-INF/schema/springbank.xsd

springbank.xsd的内容是

<?xml version="1.0" encoding="UTF-8"?>

<schema

    xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.springbank.com/schema/springbank"

    xmlns:op="http://www.springbank.com/schema/springbank" elementFormDefault="qualified">

    <element name="transaction">

        <complexType>

            <attribute name="id" type="string" use="required"/>

            <attribute name="action" type="string" use="required"/>

            <attribute name="template" type="string" use="required"/>

        </complexType>

    </element>

    <element name="template" />

    <element name="action">

        <complexType>

            <attribute name="id" type="string" use="required"/>

            <attribute name="class" type="string" use="required"/>

        </complexType>

    </element>

</schema>

schema的声明这个步骤就算完成了。接下来是要配置这个标签的解析类，这个配置在spring.handlers中完成：

http\://www.springbank.com/schema/springbank=com.demo.springtag.support.SpringbankNamespaceHandlerSupport

SpringbankNamespaceHandlerSupport类:

package com.demo.springtag.support;

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

public class SpringbankNamespaceHandlerSupport extends NamespaceHandlerSupport {

    @Override

    public void init() {

        registerBeanDefinitionParser("transaction", new TagTransactionBeanDefinitionParser());

    }

}

TagTransactionBeanDefinitionParser类

package com.demo.springtag.support;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;

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

import org.springframework.util.StringUtils;

import org.w3c.dom.Element;

/**

 * @author wangxin

 * @contact 408657544@qq.com

 * @date Jul 11, 2017

 * @Description:用于解析transaction标签

 */

public class TagTransactionBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {

    private final Logger log = LoggerFactory.getLogger(getClass());

    @Override

    protected Class<?> getBeanClass(Element element) {

        return Transaction.class;

    }

    protected void doParse(Element element, BeanDefinitionBuilder bean) {

        String id = element.getAttribute("id");

        String action = element.getAttribute("action");

        String template = element.getAttribute("template");

        if (StringUtils.hasText(id)) {

            bean.addPropertyValue("id", id);

        }

        if (StringUtils.hasText(action)) {

            bean.addPropertyValue("action", action);

        }

        if (StringUtils.hasText(template)) {

            bean.addPropertyValue("template", template);

        }

    }

}

Transaction类

package com.demo.springtag.support;

public class Transaction {

    private String id;

    private String template;

    private String action;

    public Transaction() {

        System.out.println("Bean Transaction have been created: "+toString());

    }

    public String getId() {

        return id;

    }

    public void setId(String id) {

        this.id = id;

    }

    public String getTemplate() {

        return template;

    }

    public String getAction() {

        return action;

    }

    public void setAction(String action) {

        this.action = action;

    }

    public void setTemplate(String template) {

        this.template = template;

    }

    @Override

    public String toString() {

        return "Transaction [id=" + id + ", template=" + template + "]";

    }

}

最后是测试类:

public class Main {

    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("classpath:transaction.xml");

        Transaction transaction = (Transaction)context.getBean("testTransaction");

        System.out.println(transaction.getTemplate());

    }

}

运行结果：

巴特西

自定义Spring标签

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