如何用Spring去自定义标签
主要分为五步：
-
首先我们需要一个POJO，用来测试自定义标签的值传递
-
创建xsd文件主要用来自定义标签和命名空间
-
创建解析BeanDefinition类，直接扩展Spring的AbstractSingleBeanDefinitionParser抽象类，重写它的getBeanClass和doParse方法
-
创建Handler类，扩展Spring的NamespaceHandlerSupport抽象类，重写init方法，为了注册自定义解析BeanDefinition
-
添加spring.handlers和spring.schemas文件，spring.handlers用来指定NamespaceHandler；spring.schemas用来指定自定义的xsd文件
根据以上五步，我们来实现一个自定义标签
- 创建Course类
package com.github.whvixd.demo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.beans.factory.annotation.Autowired;
public interface Entity {
@Data
@AllArgsConstructor
@NoArgsConstructor
class Course {
private String courseName;
private double score;
}
}
- 在项目的META-INF目录下添加course.xsd
<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.qilixiang1118.top/schema/course"
elementFormDefault="qualified">
<element name="course">
<complexType>
<attribute name="id" type="string"/>
<attribute name="courseName" type="string"/>
<attribute name="score" type="double"/>
</complexType>
</element>
</schema>
- 创建CourseBeanDefinitionParser和MyNamespaceHandler类
CourseBeanDefinitionParser.java
package com.github.whvixd.demo.springDemo;
import com.github.whvixd.demo.Entity;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;
/**
* Created by wangzhx on 2018/6/10.
*/
public class CourseBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
@Override
protected Class<?> getBeanClass(Element element) {
return Entity.Course.class;
}
@Override
protected void doParse(Element element, BeanDefinitionBuilder builder) {
String courseName = element.getAttribute("courseName");
String score = element.getAttribute("score");
if (StringUtils.hasLength(courseName)) {
builder.addPropertyValue("courseName", courseName);
}
if (StringUtils.hasLength(score)) {
builder.addPropertyValue("score", score);
}
}
}
NamespaceHandler.java
package com.github.whvixd.demo.springDemo;
import org.springframework.beans.factory.xml.NamespaceHandlerSupport;
/**
* Created by wangzhx on 2018/6/10.
*/
public class MyNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
registerBeanDefinitionParser("course", new CourseBeanDefinitionParser());
}
}
- 在resources的META-INF目录下创建spring.handlers和spring.schemas
spring.handlers
http\://www.qilixiang1118.top/schema/course=com.github.whvixd.demo.springDemo.MyNamespaceHandler
spring.schemas
http\://www.qilixiang1118.top/schema/course.xsd=META-INF/course.xsd
- 创建customBean.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:mycourse="http://www.qilixiang1118.top/schema/course"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.qilixiang1118.top/schema/course
http://www.qilixiang1118.top/schema/course.xsd">
<mycourse:course id="chinese" courseName="语文" score="99.0"/>
</beans>
- 测试
SpringDemo.java
package com.github.whvixd.testSpring;
import com.github.whvixd.demo.Entity;
import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
@Slf4j
public class SpringDemo {
@Test
public void myCourseBean(){
ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring/customBean.xml");
Entity.Course course = (Entity.Course) context.getBean("chinese");
System.out.println(course);
}
}
Run 打印Entity.Course(courseName=语文, score=99.0) ,成功！
