spring扩展

文章目录

spring除了可以解析自定的标签外，也可以解析用户自定义的标签。解析自定义标签需要添加一些扩展。下面以一个实例展示这个过程。

1.在resources/META-INF目录下新建文件spring-test.xsd

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

2.在resource/META-INF目录下创建spring.schema文件，并添加以下内容。

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

3.创建自定义bean解析器类UserBeanDefinitionParser,该类需要继承AbstractSingleBeanDefinitionParser

public class UserBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
    @Override
    protected Class<?> getBeanClass(Element element) {
        return User.class;
    }
    // 从element中解析并提取相应的元素
    @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);
        }
    }
}

4.创建自定义namespace处理器类MyNamespaceHandler,该类需要继承NamespaceHandlerSupport

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

5.定义一个实体类

@Data
public class User {

    private String id;
    private String userName;
    private String email;
    
    @Override
    public String toString() {
        return this.getUserName() + "--" + this.getEmail();
    }
}

6.创建一个xml文件,beans3.xml,使用自定义标签定义bean

<?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:context="http://www.springframework.org/schema/context"
       xmlns:myname="http://www.test.com/schema/user"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-4.0.xsd
            http://www.test.com/schema/user
            http://www.test.com/schema/user.xsd">

    <myname:user id="testbean" userName="aaa" email="bbb"/>
</beans>

7.定义一个测试类，测试能否成功加载该bean

public class TestApp {
    public static void main(String[] args) {
        XmlBeanFactory factory = new XmlBeanFactory(new ClassPathResource("beans3.xml"));
        User u1 = (User)factory.getBean("testbean");
        System.out.println(u1);
    }
}

8. 输出结果

aaa--bbbf