Spring的自定义标签

• 创建一个需要扩展的组件

在com.test.beans下创建User类

package com.test.beans;public class User {    private String username;    private String email;    public User() {    }    public User(String username, String email) {        this.username = username;        this.email = 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;    }    @Override    public String toString() {        return "User{" +                "username='" + username + '\'' +                ", email='" + email + '\'' +                '}';    }}

• 定义一个XSD文件描述组件内容

在resources下创建META-INF文件夹，在META-INF下创建user.xsd文件，文件内容为：

<?xml version="1.0" encoding="UTF-8" ?><schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.test.tag.com/schema/user"        elementFormDefault="qualified">    <element name="user">        <complexType>            <attribute name="id" type="string"/>            <attribute name="username" type="string"/>            <attribute name="email" type="string"/>        </complexType>    </element></schema>

• 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

在com.test.tag包下创建UserBeanDefinitionParser类，继承自AbstractSingleBeanDefinitionParser类

package com.test.tag;import org.springframework.beans.factory.support.BeanDefinitionBuilder;import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;import org.springframework.util.StringUtils;import org.w3c.dom.Element;import com.test.beans.User;public class UserBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {    @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);        }    }}

• 创建一个Handler文件，扩展自NamespaceHandlerSupport，目的是将组件注册到Spring容器

在com.test.tag包下创建UserNamespaceHandler类，继承自NamespaceHandlerSupport类

package com.test.tag;import org.springframework.beans.factory.xml.NamespaceHandlerSupport;public class MyNamespaceHandler extends NamespaceHandlerSupport {    @Override    public void init() {        registerBeanDefinitionParser("user", new UserBeanDefinitionParser());    }}

• 在META-INF下编写Spring.schemas和Spring.handlers文件

Spring.handlers文件:

http\://www.test.tag.com/schema/user=com.test.tag.UserNamespaceHandler

Spring.schemas文件：

http\://www.test.tag.com/schema/user.xsd=META-INF/user.xsd

• 标签的使用

1.在resources下的spring-context.xml文件中配置

<?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:bean="http://www.test.tag.com/schema/user"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.test.tag.com/schema/user http://www.test.tag.com/schema/user.xsd">    <bean:user id="test" username="张三" email="[e-mail]"/></beans>

2.测试

package com.test;import org.junit.Test;import org.springframework.context.support.ClassPathXmlApplicationContext;import com.test.beans.User;public class TestTag {    @Test    public void testTag() {        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("spring-context.xml");        User user = (User) ctx.getBean("test");        System.out.println(user.getUsername() + " : " + user.getEmail());    }}

3.输出

张三 : [e-mail]