Spring自定义标签的使用

在Spring中完成一个自定义标签需要以下步骤：

1. 设计配置属性和定义JavaBean
2. 编写XSD文件
3. 编写BeanDefinitionParser标签解析类
4. 编写调用标签解析类的NamespaceHandler类
5. 编写spring.handlers和spring.schemas以供Spring读取
6. 在Spring使用

工程pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.morning</groupId>
	<artifactId>morning-spring</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>morning-spring</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-aop</artifactId>
			<version>5.1.9.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>5.1.9.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>5.1.9.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context-support</artifactId>
			<version>5.1.9.RELEASE</version>
		</dependency>
	</dependencies>

</project>

首先第一步，设置配置属性和JavaBean

package com.morning.morningspring.config;

public class User {
    private String userName;
    private String email;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

编写xsd文件

user.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://www.morning.com/schema/user"
           elementFormDefault="qualified">
    <xsd:import namespace="http://www.springframework.org/schema/beans"/>

    <xsd:element name="user">
        <xsd:complexType>
            <xsd:attribute name="id" type="xsd:string"/>
            <xsd:attribute name="userName" type="xsd:string"/>
            <xsd:attribute name="email" type="xsd:string"/>
        </xsd:complexType>
    </xsd:element>
</xsd:schema>

编写BeanDefinitionParser标签解析类

package com.morning.morningspring.parser;

import com.morning.morningspring.config.User;
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 UserDefinitionParser extends AbstractSingleBeanDefinitionParser {

    public UserDefinitionParser() {
    }

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

    @Override
    protected void doParse(Element element, BeanDefinitionBuilder builder) {
        String userName = element.getAttribute("userName");
        String email = element.getAttribute("email");

        if (StringUtils.hasText(userName)) {
            builder.addPropertyValue("userName", userName);
        }

        if (StringUtils.hasText(email)) {
            builder.addPropertyValue("email", email);
        }

    }
}

编写调用标签解析类的NamespaceHandler类

package com.morning.morningspring.handler;

import com.morning.morningspring.parser.UserDefinitionParser;
import org.springframework.beans.factory.xml.NamespaceHandlerSupport;

public class CustomNamespaceHandler  extends NamespaceHandlerSupport {
    public void init() {
        registerBeanDefinitionParser("user", new UserDefinitionParser());
    }
}

编写spring.handlers和spring.schemas以供Spring读取

spring.handlers文件 http\://www.morning.com/schema/user=com.morning.morningspring.handler.CustomNamespaceHandler spring.schemas文件http\://www.morning.com/schema/user.xsd=META-INF/namespace/user.xsd

工程打包 mvn install

在Spring使用

<?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:customer="http://www.morning.com/schema/user"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.morning.com/schema/user http://www.morning.com/schema/user.xsd">

    <customer:user id="user" userName="moring" email="12345678@outlook.com" />
</beans>

在代码中通过@Autowired或者@Resource即可引入该bean