Spring自定义标签

    如果要开发一个spring自定义的标签比如： 

<pre:strategy id="strategyFrist" interface="org.test.spring.schema.strategy.FristStrategy"
		url="tcp://strategy/frist" />

    扩展Spring自定义标签大致需要如下几步： 

1. 创建需要扩展的组件
2. 定义XSD文件描述组件内容
3. 创建一个文件，实现BeanDefinitionParser接口，用来解析XSD文件中的定义和组件定义
4. 创建Handler文件，扩展字NamespaceHandlerSupport,目的是将组件注册到Spring容器
5. 编写Spring.handlers和Spring.schemas文件

    具体步骤如下：

    1、创建maven工程spring-schema，添加spring相应jar包     

<dependency>
	 <groupId>org.springframework</groupId>
	 <artifactId>spring-beans</artifactId>
	 <version>${spring.version}</version>
	 <optional>true</optional>
</dependency>
<dependency>
	 <groupId>org.springframework</groupId>
	 <artifactId>spring-context</artifactId>
	 <version>${spring.version}</version>
	 <optional>true</optional>
</dependency>    

    2、创建一个bean，接收自定义标签属性，如StrategyBean，这里实现了FactoryBean接口，为了将自定义的标签解析完成后注入spring容器    

public class StrategyBean implements FactoryBean<Object>{

       private String id;

       private String url;

       private Class<?> interfaceName;


       @Override

       public Object getObject() throws Exception {

              return interfaceName.newInstance();

       }
     

       @Override

       public Class<?> getObjectType() {

             return interfaceName;

       }

       @Override

       public boolean isSingleton() {

              return true;

       }

       //省略get/set方法

}

    3、在工程的META-INF文件夹下定义一个XSD文件描述组件内容，如src/main/resources/META-INF/strategy.xsd  

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.shijun.com/schema/strategy" xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="strategy">

    <xs:complexType>

      <xs:simpleContent>

        <xs:extension base="xs:string">

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

          <xs:attribute type="xs:anySimpleType" name="interface" use="required"/>

          <xs:attribute type="xs:string" name="url" use="required"/>

        </xs:extension>

      </xs:simpleContent>

    </xs:complexType>

  </xs:element>

</xs:schema>

   4、实现BeanDefinitionParser接口，用来解析XSD文件中的定义和组件定义，如StrategyBeanDefinitionParser     

 /**
 * 配置解析器
 * @author shijun03
 */
public class StrategyBeanDefinitionParser extends AbstractSingleBeanDefinitionParser{

	@Override
	protected Class<?> getBeanClass(Element element) {
		return StrategyBean.class;
	}

	@Override
	protected void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
		String id = element.getAttribute("id");
		String url = element.getAttribute("url");
		String interfaceName = element.getAttribute("interface");
		
		if(StringUtils.hasText(id)){
			//判断bean是否已经注册
			boolean hasRegistry  = parserContext.getRegistry().containsBeanDefinition(id);
			if(hasRegistry){
				throw new IllegalArgumentException("bean has registry ,please check bean ,id = "+id);
			}
			builder.addPropertyValue("id", id);
		}
		
		if(StringUtils.hasText(url)){
			builder.addPropertyValue("url", url);
		}
		
		if(StringUtils.hasText(interfaceName)){
			Class<?> forName;
			try {
				forName = Class.forName(interfaceName);
			} catch (ClassNotFoundException e) {
				throw new IllegalArgumentException("interface class not found", e);
			}
			builder.addPropertyValue("interfaceName", forName);
		}
	}
	
}

    5、 创建Handler文件，扩展自NamespaceHandlerSupport，目的是将组件注册到Spring容器中，如StrategyBeanHandler    

/**
 * 解析器注入
 * @author shijun03
 */
public class StrategyBeanHandler extends NamespaceHandlerSupport{

	@Override
	public void init() {
		registerBeanDefinitionParser("strategy", new StrategyBeanDefinitionParser());
	}

}

    6、编写Spring.handlers和Spring.schemas文件 

 

    路径：src/main/resources/META-INF/Spring.handlers    

http\://www.shijun.com/schema/strategy=com.sjz.spring.schema.StrategyBeanHandler

 

    路径：src/main/resources/META-INF/Spring.schemas     

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

 

    7、创建测试配置文件 

    新建spring工程，引入前面创建的工程jar以及其他的jar   

<dependency>
       <groupId>com.sjz</groupId>
       <artifactId>spring-schema</artifactId>
       <version>0.0.1-SNAPSHOT</version>
</dependency>

//…省略其他的jar

    创建FristStrategy对象    

public class FristStrategy {

       public String hello(){

              return "hello schema";

       }

}

    在src/main/resources下添加配置文件，如下spring-strategy.xml    

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

	<pre:strategy id="strategyFrist" interface="org.test.spring.schema.strategy.FristStrategy"
		url="tcp://strategy/frist" />

</beans>

    通过Configuration注解引入spring-strategy.xml配置文件    

@Configuration

@ImportResource(locations="spring-strategy.xml")

public class StrategyConfig {

}

    测试   

@SpringBootApplication

public class App {

       public static void main(String[] args) {

              ConfigurableApplicationContext context = SpringApplication.run(App.class, args);

              FristStrategy bean = context.getBean(FristStrategy.class);

              System.out.println("数据调用结果集========"+bean.hello());

       }

}

    输出如下   

数据调用结果集========hello schema

   

    8、详细代码    

spring自定义标签工程：https://github.com/ejshi/spring-schema.git

测试工程：https://github.com/ejshi/es/tree/master/test-spring-schema