spring源码深刻：自定义spring标签（schema）识别与运用

自定义标签做用在很是复杂须要抽象出来或独立出来作本身的开源框架所必备基础

0，咱们经常使用cache标签为栗

一、先看看咱们经常使用spring标签cache如何来的

      

2:spring.handlers ：

http\://www.springframework.org/schema/cache=org.springframework.cache.config.CacheNamespaceHandler

3：spring-cache.xsd

<xsd:schema xmlns="http://www.springframework.org/schema/cache"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:tool="http://www.springframework.org/schema/tool"
targetNamespace="http://www.springframework.org/schema/cache"
elementFormDefault="qualified"
attributeFormDefault="unqualified">

-------查找咱们的：annotation-driven节点及节点下属性

<xsd:element name="annotation-driven">
<xsd:complexType>
<xsd:annotation>
<xsd:documentation source="java:org.springframework.cache.annotation.AnnotationCacheOperationDefinitionSource"><![CDATA[
Indicates that cache configuration is defined by Java 5
annotations on bean classes, and that proxies are automatically
to be created for the relevant annotated beans.


The default annotations supported are Spring's @Cacheable, @CachePut and @CacheEvict. If
spring-context-support and the JSR-107 API are on the classpath, additional proxies are
automatically created for JSR-107 annotated beans, that is @CacheResult, @CachePut,
@CacheRemove and @CacheRemoveAll.


See org.springframework.cache.annotation.EnableCaching Javadoc
for information on code-based alternatives to this XML element.
]]></xsd:documentation>
</xsd:annotation>
<xsd:attribute name="cache-manager" type="xsd:string" default="cacheManager">
<xsd:annotation>
<xsd:documentation source="java:org.springframework.cache.CacheManager"><![CDATA[
The bean name of the CacheManager that is to be used to retrieve the backing
caches. A default CacheResolver will be initialized behind the scenes with
this cache manager (or "cacheManager" if not set). For more fine-grained
management of the cache resolution, consider setting the 'cache-resolver'
attribute.


Note that this attribute is still mandatory if you are using JSR-107 as an
additional exception cache resolver should be created and requires a CacheManager
to do so.
]]></xsd:documentation>
<xsd:appinfo>
<tool:annotation kind="ref">
<tool:expected-type type="org.springframework.cache.CacheManager"/>
</tool:annotation>
</xsd:appinfo>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="cache-resolver" type="xsd:string">
<xsd:annotation>
<xsd:documentation source="java:org.springframework.cache.interceptor.CacheResolver"><![CDATA[
The bean name of the CacheResolver that is to be used to resolve the backing caches.


This attribute is not required, and only needs to be specified as an alternative to
the 'cache-manager' attribute. See the javadoc of CacheResolver for more details.
]]></xsd:documentation>
<xsd:appinfo>
<tool:annotation kind="ref">
<tool:expected-type type="org.springframework.cache.interceptor.CacheResolver"/>
</tool:annotation>
</xsd:appinfo>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="key-generator" type="xsd:string">
<xsd:annotation>
<xsd:documentation source="java:org.springframework.cache.interceptor.KeyGenerator"><![CDATA[
The bean name of the KeyGenerator that is to be used to retrieve the backing caches.


This attribute is not required, and only needs to be specified
explicitly if the default strategy (DefaultKeyGenerator) is not sufficient.
]]></xsd:documentation>
<xsd:appinfo>
<tool:annotation kind="ref">
<tool:expected-type type="org.springframework.cache.interceptor.KeyGenerator"/>
</tool:annotation>
</xsd:appinfo>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="error-handler" type="xsd:string">
<xsd:annotation>
<xsd:documentation source="java:org.springframework.cache.interceptor.CacheErrorHandler"><![CDATA[
The bean name of the CacheErrorHandler that is to be used to handle cache-related errors.


This attribute is not required, and only needs to be specified
explicitly if the default strategy (SimpleCacheErrorHandler) is not sufficient.
]]></xsd:documentation>
<xsd:appinfo>
<tool:annotation kind="ref">
<tool:expected-type type="org.springframework.cache.interceptor.CacheErrorHandler"/>
</tool:annotation>
</xsd:appinfo>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="mode" default="proxy">
<xsd:annotation>
<xsd:documentation><![CDATA[
Should annotated beans be proxied using Spring's AOP framework,
or should they rather be weaved with an AspectJ transaction aspect?


AspectJ weaving requires spring-aspects.jar on the classpath,
as well as load-time weaving (or compile-time weaving) enabled.


Note: The weaving-based aspect requires the @Cacheable and @CacheInvalidate
annotations to be defined on the concrete class. Annotations in interfaces
will not work in that case (they will rather only work with interface-based proxies)!
]]></xsd:documentation>
</xsd:annotation>
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="proxy"/>
<xsd:enumeration value="aspectj"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="proxy-target-class" type="xsd:boolean" default="false">
<xsd:annotation>
<xsd:documentation><![CDATA[
Are class-based (CGLIB) proxies to be created? By default, standard
Java interface-based proxies are created.


Note: Class-based proxies require the @Cacheable and @CacheInvalidate annotations
to be defined on the concrete class. Annotations in interfaces will not work
in that case (they will rather only work with interface-based proxies)!
]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="order" type="xsd:token">
<xsd:annotation>
<xsd:documentation source="java:org.springframework.core.Ordered"><![CDATA[
Controls the ordering of the execution of the cache advisor
when multiple advice executes at a specific joinpoint.
]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
</xsd:element>

所以，咱们了解了spring标签基本作法，但为何这么作？

      基本原理在于bean的ioc容器和解析机制，具体的实用待下一篇发表

      另，这样的扩展作法也是开源框架自定义标签通常的作法，有利于扩展，好比你们经常使用的dubbo标签