前言
之前我們聊過自定義的SPI如何與spring進行整合，今天我們就來聊下如何通過自定義標籤將spi物件注入到spring容器中
實現套路
1、自定義xsd
示例：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:tool="http://www.springframework.org/schema/tool"
xmlns="http://lybgeek.github.com/schema/spi"
targetNamespace="http://lybgeek.github.com/schema/spi">
<xsd:import namespace="http://www.w3.org/XML/1998/namespace"/>
<xsd:import namespace="http://www.springframework.org/schema/beans"
schemaLocation="http://www.springframework.org/schema/beans/spring-beans.xsd"/>
<xsd:import namespace="http://www.springframework.org/schema/tool"/>
<xsd:annotation>
<xsd:documentation>
<![CDATA[ Namespace support for spi services ]]></xsd:documentation>
</xsd:annotation>
<xsd:complexType name="scanType">
<xsd:attribute name="id" type="xsd:ID">
<xsd:annotation>
<xsd:documentation><![CDATA[ The unique identifier for a bean. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="basePackages" type="xsd:string" use="required">
<xsd:annotation>
<xsd:documentation><![CDATA[ Specify the spi package name to scan, multiple scan packages are separated by commas ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
<xsd:complexType name="interceptorType">
<xsd:attribute name="id" type="xsd:ID">
<xsd:annotation>
<xsd:documentation><![CDATA[ The unique identifier for a bean. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="class" type="xsd:string" use="required">
<xsd:annotation>
<xsd:documentation><![CDATA[ Interceptor class name]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
<xsd:complexType name="interceptorChainType">
<xsd:choice>
<xsd:element ref="interceptor" minOccurs="1" maxOccurs="unbounded"/>
</xsd:choice>
</xsd:complexType>
<xsd:element name="scan" type="scanType">
<xsd:annotation>
<xsd:documentation><![CDATA[ The scan config ]]></xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="interceptor" type="interceptorType">
<xsd:annotation>
<xsd:documentation><![CDATA[ The interceptor config ]]></xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="interceptorChain" type="interceptorChainType">
<xsd:annotation>
<xsd:documentation><![CDATA[ The interceptorChainType config ]]></xsd:documentation>
</xsd:annotation>
</xsd:element>
</xsd:schema>
ps： 如果對xsd不熟悉的朋友，可以參考如下連結
https://www.w3school.com.cn/schema/index.asp
2、自定義解析BeanDefinitionParser解析器
示例：
public class AnnotationBeanDefinitionParser implements BeanDefinitionParser {
private final Class<?> beanClass;
public AnnotationBeanDefinitionParser(Class<?> beanClass) {
this.beanClass = beanClass;
}
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
String packageToScan = element.getAttribute("basePackages");
String[] packagesToScan = trimArrayElements(commaDelimitedListToStringArray(packageToScan));
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass);
beanDefinition.setLazyInit(false);
beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(0,packagesToScan);
String beanName = BeanUtils.generateBeanName(element,"id",parserContext,beanClass.getName());
parserContext.getRegistry().registerBeanDefinition(beanName,beanDefinition);
return beanDefinition;
}
}3、定義NamespaceHandler實現類處理自定義標籤的處理器
示例：
public class SpiNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
registerBeanDefinitionParser("scan", new AnnotationBeanDefinitionParser(SpiAnnotationPostProcessor.class));
}
}4、將寫入處理器、標籤的位置寫入spring.handlers、spring.schemas中
示例：
spring.handlers
http\://lybgeek.github.com/schema/spi=com.github.lybgeek.spring.schema.SpiNamespaceHandlerspring.schemas
http\://lybgeek.github.com/schema/spi/spi.xsd=META-INF/spi/spi.xsd注： spring.handlers、spring.schemas需放置在resource/META-INF目錄底下
示例演示
1、配置xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:spi="http://lybgeek.github.com/schema/spi"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
http://lybgeek.github.com/schema/spi http://lybgeek.github.com/schema/spi/spi.xsd">
<spi:scan basePackages="com.github.lybgeek"></spi:scan>
2、在啟動類上匯入xml
@SpringBootApplication
@ImportResource(locations = "classpath:/spi.xml")
public class SpiTestXmlApplication {
public static void main(String[] args) throws Exception{
SpringApplication.run(SpiTestXmlApplication.class);
}
}3、驗證SPI是否注入spring容器
@Override
public void run(ApplicationArguments args) throws Exception {
applicationContext.getBeansOfType(SpringSqlDialect.class)
.forEach((beanName,bean) -> System.out.println(beanName + "-->" + bean));
}控制檯輸入如下
springMysqlDialect-->com.github.lybgeek.dialect.mysql.SpringMysqlDialect@73041b7d
mysql-hello-->com.github.lybgeek.dialect.mysql.SpringMysqlDialect@574059d5
springOracleDialect-->com.github.lybgeek.dialect.oracle.SpringOracleDialect@4a50d04a說明已經匯入到spring容器中
總結
自從spring3+開始引入註解驅動後，在新專案基本上很少會使用xml，但如果是一些老舊的專案，大家如果想實現自定義標籤注入到spring，就可以使用本文的方式。
套路就是如下
- 1、自定義xsd
- 2、自定義解析BeanDefinitionParser解析器
- 3、定義NamespaceHandler實現類處理自定義標籤的處理器
- 4、將寫入處理器、標籤的位置寫入spring.handlers、spring.schemas中
本文的實現也是相對簡單，如果想深入使用，推薦看看dubbo自定義spring標籤