dubbo源码学习（三）基础知识：spring 自定义标签

初学dubbo的源码，只做尝试性的去学习，做为自己学习的一个记录，各位看官如果觉得写的有错误或理解的不对，请在留言区告诉我，互相学习。本人能力有限，有大神进入 时请指点。

我们在做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chewl.xsd

实体类如下：

public class Chewl {

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 ChewlBeanDefinitionParserS extends AbstractSingleBeanDefinitionParser {
private final Class<?> beanClass;

private final boolean required;

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

protected Class getBeanClass(Element element) {
return Chewl.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 ChewlNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
//实现init方法,解析chewl标签
registerBeanDefinitionParser("chewl",new ChewlBeanDefinitionParserS(Chewl.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.oschina.net/schema/chewl=springNameSpace.ChewlNamespaceHandler

spring.schemas配置

http\://www.oschina.net/schema/chewl/chewl.xsd=META-INF/chewl.xsd

chewl.xsd的配置

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema
xmlns="http://www.oschina.net/schema/chewl"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:beans="http://www.springframework.org/schema/beans"
targetNamespace="http://www.oschina.net/schema/chewl"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xsd:import namespace="http://www.springframework.org/schema/beans" />
<!-- 定义element名,chewlType对应了bean的属性  -->
<xsd:element name="chewl" type="chewlType">
<xsd:annotation>
<xsd:documentation><![CDATA[ The chewl 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="chewlType">
<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 chewl name. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="age" type="xsd:int">
<xsd:annotation>
<xsd:documentation><![CDATA[ The chewl age. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="profession" type="xsd:string">
<xsd:annotation>
<xsd:documentation><![CDATA[ The chewl profession. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="address" type="xsd:string">
<xsd:annotation>
<xsd:documentation><![CDATA[ The chewl address. ]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="phone" type="xsd:string">
<xsd:annotation>
<xsd:documentation><![CDATA[ The chewl 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.oschina.net/schema/chewl"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.oschina.net/schema/chewl http://www.oschina.net/schema/chewl/chewl.xsd">

<common:chewl 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");
Chewl chewl = (Chewl) context.getBean("test");
System.out.println(chewl.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。