dubbo源码学习(二) : spring 自定义标签

做dubbo的配置时很容易发现，dubbo有一套自己的标签，提供给开发者配置，其实每一个标签对应着一个 实体，在容器启动的时候，dubbo会对所有的配置进行解析然后将解析后的内容设置到实体里，最终dubbo会根据实体中的值生成贯穿全局的统一URL。利用自定义标签使配置简单明了化，与spring完美融合。
下面自己写一个自定义标签，主要需要如下 几个步骤：

1、编写实体类
2、编写Parser解析类
3、编写NameSpaceHandle类
4、配置spring.handlers
5、配置spring.schemas
6、配置customTag .xsd

标签实体类如下：
public class CustomTag {

    private String id;

    private String name;

    private Integer age;

    private String profession;

    private String address;

    private String phone;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

    public String getProfession() {
        return profession;
    }

    public void setProfession(String profession) {
        this.profession = profession;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String toString(){
        StringBuffer sb = new StringBuffer();
        sb.append(id + "\n");
        sb.append(name + "\n");
        sb.append(age + "\n");
        sb.append(profession + "\n");
        sb.append(address + "\n");
        sb.append(phone + "\n");
        return sb.toString();
    }
}

标签的解析类如下:
public class CustomTagBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
    private final Class<?> beanClass;

    private final boolean required;

    public CustomTagBeanDefinitionParser (Class<?> beanClass, boolean required) {
        this.beanClass = beanClass;
        this.required = required;
    }

    protected Class getBeanClass(Element element) {
        return CustomTag.class;
    }

    protected void doParse(Element element, BeanDefinitionBuilder builder) {
        //通过配置文件获取相应的值，设置到bean的属性中
        String id = element.getAttribute("id");
        String name = element.getAttribute("name");
        String age = element.getAttribute("age");
        String profession = element.getAttribute("profession");
        String address = element.getAttribute("address");
        String phone = element.getAttribute("phone");
        if (StringUtils.hasText(id)) {
            builder.addPropertyValue("id", id);
        }
        if (StringUtils.hasText(name)) {
            builder.addPropertyValue("name", name);
        }
        if (StringUtils.hasText(age)) {
            builder.addPropertyValue("age", age);
        }
        if (StringUtils.hasText(profession)) {
            builder.addPropertyValue("profession", profession);
        }
        if (StringUtils.hasText(address)) {
            builder.addPropertyValue("address", address);
        }
        if (StringUtils.hasText(phone)) {
            builder.addPropertyValue("phone", phone);
        }
    }
   
}

NameSpaceHandle类如下：
public class CustomTagNamespaceHandler extends NamespaceHandlerSupport {
    @Override
    public void init() {
        //实现init方法,解析CustomTag标签
        registerBeanDefinitionParser("customTag",new CustomTagBeanDefinitionParser(CustomTag.class,true));
    }
}

spring.handlers配置，前面那一串其实可以随便配置，只要一会和后面的配置一致即可
http\://www.51gitee.net/schema/customTag=springNameSpace.CustomTagNamespaceHandler

spring.schemas配置
http\://www.51gitee.net/schema/customTag/customTag.xsd=META-INF/customTag.xsd

customTag.xsd的配置
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema
        xmlns="http://www.51gitee.net/schema/customTag"
        xmlns:xsd="http://www.w3.org/2001/XMLSchema"
        xmlns:beans="http://www.springframework.org/schema/beans"
        targetNamespace="http://www.51gitee.net/schema/customTag"
        elementFormDefault="qualified"
        attributeFormDefault="unqualified">
    <xsd:import namespace="http://www.springframework.org/schema/beans" />
    <!-- 定义element名, customTagType对应了bean的属性  -->
    <xsd:element name="customTag" type="customTagType">
        <xsd:annotation>
            <xsd:documentation><![CDATA[ The customTag config ]]></xsd:documentation>
        </xsd:annotation>
    </xsd:element>
    <!--  配置各属性值，有点像Mybatis配置对应的model   -->
    <xsd:complexType name="customTagType">
        <xsd:attribute name="id" type="xsd:ID">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The unique identifier for a bean. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="name" type="xsd:string" use="required">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The customTag name. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="age" type="xsd:int">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The customTag age. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="profession" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The customTag profession. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="address" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The customTag address. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="phone" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation><![CDATA[ The customTag phone. ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
    </xsd:complexType>

</xsd:schema>

最后测试
在新建一个spring的配置文件如下

<?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:common="http://www.51gitee.net/schema/customTag"
       xsi:schemaLocation="
     http://www.springframework.org/schema/beans
     http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
     http://www.oschina.net/schema/customTag
     http://www.oschina.net/schema/customTag/customTag.xsd">

    <common:customTag id="test"  name="chewenliang" address="bei jing" age="12" phone="18618152379" profession="技术" />

</beans>

在java代码中测试
public class TestNameSpace {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-test.xml");
        CustomTag customTag= (CustomTag) context.getBean("test");
        System.out.println(customTag.toString());
    }
}

输出结果：
    test 
    chewenliang 
    12 
    技术 
    bei jing 
    18618152379 

spring的自定义标签自己很容易实现，具体要看在实际项目中如何正确的实用它，接下来会记录dubbo是如何解析、暴露服务。

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