Spring5之自定义标签的使用及源码的判断节点的解析

@派大星

发布于 2023-06-28 14:36:20

1320

发布于 2023-06-28 14:36:20

文章被收录于专栏：码上遇见你

自定义标签的使用

扩展Spring自定义标签配置大概需要以下几步：

创建一个需要扩展的组件
定义一个XSD文件，用于描述组件内容
创建一个实现AbstractSingleBeanDefinitionParser接口的类，用来解析XSD文件中的定义和组件定义
创建一个Handler，继承NamespaceHandlerSupport，用于将组件注册到Spring容器
编写Spring.handlers和Spring.schemes文件

接下来我们按着上面的步骤进行创建，这里我会创建两个组件，也可以创建一个，大同小异，后面演示用。

组件

package com.vipbbo.spring.bean.customtag2;

/**
 * 需要扩展的组件
 */
public class User {
 @Override
 public String toString() {
  return "User{" +
    "name='" + name + '\'' +
    ", age=" + age +
    '}';
 }

 private String name;
 private int age;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public int getAge() {
  return age;
 }

 public void setAge(int age) {
  this.age = age;
 }
}

package com.vipbbo.spring.bean.customtag2;

/**
 * 需要扩展的组件
 */
public class Phone {
 private String color;
 private int size;
 private String remark;

 public String getColor() {
  return color;
 }

 public void setColor(String color) {
  this.color = color;
 }

 public int getSize() {
  return size;
 }

 public void setSize(int size) {
  this.size = size;
 }

 public String getRemark() {
  return remark;
 }

 public void setRemark(String remark) {
  this.remark = remark;
 }

 @Override
 public String toString() {
  return "Phone{" +
    "color='" + color + '\'' +
    ", size=" + size +
    ", remark='" + remark + '\'' +
    '}';
 }
}

定义XSD文件

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

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns="http://hellospring.vipbbo.com/schema/custom"
   targetNamespace="http://hellospring.vipbbo.com/schema/custom"
   elementFormDefault="qualified">
 <xsd:element name="user">
  <xsd:complexType>
   <xsd:attribute name="id" type="xsd:string">
   </xsd:attribute>
   <xsd:attribute name="name" type="xsd:string">
   </xsd:attribute>
   <xsd:attribute name="age" type="xsd:int">
   </xsd:attribute>
  </xsd:complexType>
 </xsd:element>
 <xsd:element name="phone">
  <xsd:complexType>
   <xsd:attribute name="id" type="xsd:string">
   </xsd:attribute>
   <xsd:attribute name="color" type="xsd:string">
   </xsd:attribute>
   <xsd:attribute name="size" type="xsd:int">
   </xsd:attribute>
   <xsd:attribute name="remark" type="xsd:string">
   </xsd:attribute>
  </xsd:complexType>
 </xsd:element>
</xsd:schema>

这里需要注意的是xmlns和targetNamespace要保持一致

Parser类

该类是一个继承了AbstractSingleBeanDefinitionParser的Parser类，并实现了getBeanCladd()和doParse()两个方法。主要用于解析XSD文件中的定义和组件的定义，这里我定义了两个Parser类，一个解析User，一个解析Phone

package com.vipbbo.spring.bean.customtag2;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;

public class UserBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
 @Override
 protected Class<?> getBeanClass(Element element) {
  return User.class;
 }

 @Override
 protected void doParse(Element element, BeanDefinitionBuilder builder) {
  String name = element.getAttribute("name");
  String age = element.getAttribute("age");
  if (StringUtils.hasText(name)){
   builder.addPropertyValue("name",name);
  }
  if (StringUtils.hasText(age)) {
   builder.addPropertyValue("age",age);
  }
 }
}

package com.vipbbo.spring.bean.customtag2;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;

public class PhoneBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
 @Override
 protected Class<?> getBeanClass(Element element) {
  return Phone.class;
 }

 @Override
 protected void doParse(Element element, BeanDefinitionBuilder builder) {
  String color = element.getAttribute("color");
  String size = element.getAttribute("size");
  String remark = element.getAttribute("remark");
  if (StringUtils.hasText(color)) {
   builder.addPropertyValue("color",color);
  }
  if (StringUtils.hasText(size)) {
   builder.addPropertyValue("size",size);
  }
  if (StringUtils.hasText(remark)) {
   builder.addPropertyValue("remark",remark);
  }
 }
}

Handler类

定义一个Handler类，继承NamespaceHandlerSupport，主要目的是将上面定义的解析器Parser类注册到Spring容器中。

package com.vipbbo.spring.bean.customtag2;

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

public class CustomNameSpaceHandler extends NamespaceHandlerSupport {
 @Override
 public void init() {
  registerBeanDefinitionParser("user",new UserBeanDefinitionParser());
  registerBeanDefinitionParser("phone",new PhoneBeanDefinitionParser());
 }
}

这个类主要是将解析器 UserBeanDefinitionParser和 PhoneBeanDefinitionParser 的实例放到全局的Map中，key为user和phone。看源码

看源码(NamespaceHandlerSupport.java)

private final Map<String, BeanDefinitionParser> parsers = new HashMap<>();

//省略......

protected final void registerBeanDefinitionParser(String elementName, BeanDefinitionParser parser) {
  this.parsers.put(elementName, parser);
 }

spring.handlers和spring.schemas

编写Spring.handlers和spring.schemas文件，默认放在META-INF文件夹下

http://hellospring.vipbbo.com/schema/custom=com.vipbbo.spring.bean.customtag2.CustomNameSpaceHandler

http://hellospring.vipbbo.com/schema/tag/customtag.xsd=META-INF/customtag.xsd

测试的配置文件

<?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:customtag="http://hellospring.vipbbo.com/schema/custom"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
  http://hellospring.vipbbo.com/schema/custom
  http://hellospring.vipbbo.com/schema/tag/customtag.xsd
  ">
 <customtag:user id="user" name="paidaxing" age="18"/>
 <customtag:phone id="phone" color="black" size="14" remark="pro"/>

</beans>

xmlns:customtag表示customtag的命名空间是http://hellospring.vipbbo.com/schema/custom，在文章开头的判断处 if (delegate.isDefaultNamespace(ele)) 肯定会返回false，将进入到自定义标签的解析

测试类

package com.vipbbo.spring.bean.customtag2;

import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class CustomTagTest {

 @Test
 public void TagTest(){
  ApplicationContext ac =
    new ClassPathXmlApplicationContext("custom-tag2.xml");
  User user = (User) ac.getBean("user");
  Phone phone = (Phone) ac.getBean("phone");

  System.out.println(user);
  System.out.println(phone);
 }
}

测试截图