最开始使用spring框架的时候,对于其配置文件xml,只是网上得知其使用方法,而不明其意。最近想着寻根问底的探究一下。以下是本文主要内容:
1、配置文件示例。
- <?xml version="1.0" encoding="UTF-8"?>
- <beans xmlns="http://www.springframework.org/schema/beans"
- xmlns:mvc="http://www.springframework.org/schema/mvc"
- xmlns:tx="http://www.springframework.org/schema/tx"
- xmlns:aop="http://www.springframework.org/schema/aop"
- xmlns:context="http://www.springframework.org/schema/context"
- xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
- 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.xsd
- http://www.springframework.org/schema/mvc
- http://www.springframework.org/schema/mvc/spring-mvc.xsd
- http://www.springframework.org/schema/tx
- http://www.springframework.org/schema/tx/spring-tx.xsd
- http://www.springframework.org/schema/aop
- http://www.springframework.org/schema/aop/spring-aop.xsd "
- default-autowire="byName">
- </beans>
上 面是我们最常用的applicationContext.xml的配置文件的最开始部分,很多时候我们只是知道这些必须添加,但为什么,添加哪些都不甚清 楚。我们知道spring在启动的时候会验证 xml文档,这些引入的schema即用来验证配置文件的xml文档语法的正确性。下面先来看看如何验证xml文档验证的相关知识。
2、xml的schema约束
先来说说xml文档的schema约束,它定义了xml文档的结构,内容和语法,包括元素和属性、关系的结构以及数据类型等等。有以下几点需要遵循:
1) 、所有的标签和属性都需要Schema来定义。(schema本身由w3c来定义)。
2)、所有的schema文件都需要以个ID,这里我们称之为 namespace,其值时一个url,通常是这个xml的xsd文件的地址。
3)、namespace值由 targetNamespace属性来指定
4)、引入一个schema约束,使用属性xmlns,属性值即为对应schema文件的命名空间 nameSpace。
5)、如果引入的schema非w3c组织定义的,必须指定schema文件的位置,schema文件的位置由 schemaLocation来指定。
6)、引入多个schema文件需要使用 别名。别名形式如下: xmlns:alias。
3、对于上述配置文件的详细解读
1)、 声明默认的名称空间(xmlns="http://www.springframework.org/schema/beans")
2)、 声明XML Schema实例名称空间(http://www.w3.org/2001/XMLSchema-instance),并将xsi前缀与该名称空间绑定, 这样模式处理器就可以识别xsi:schemaLocation属性。XML Schema实例名称空间的前缀通常使用xsi
3)、 使 用xsi:schemaLocation属性指定名称空间(http://www.springframework.org/schema/beans) 和模式位置(http://www.springframework.org/schema/beans/spring-beans.xsd)相关。 XML Schema推荐标准中指出,xsi:schemaLocation属性可以在实例中的任何元素上使用,而不一定是根元素,不 过,xsi:schemaLocation属性必须出现在它要验证的任何元素和属性之前。
4)、使用别名引入多个schema文件。如上述 xmlns:mvc 、xmlns:tx 、xmlns:context等等。
4、使用带版本号的xsd文件有何弊端?
- http://www.springframework.org/schema/context=org.springframework.context.config.ContextNamespaceHandler
- http://www.springframework.org/schema/jee=org.springframework.ejb.config.JeeNamespaceHandler
- http://www.springframework.org/schema/lang=org.springframework.scripting.config.LangNamespaceHandler
- http://www.springframework.org/schema/task=org.springframework.scheduling.config.TaskNamespaceHandler
- http://www.springframework.org/schema/cache=org.springframework.cache.config.CacheNamespaceHandler
- http://www.springframework.org/schema/context/spring-context-2.5.xsd=org/springframework/context/config/spring-context-2.5.xsd
- http://www.springframework.org/schema/context/spring-context-3.0.xsd=org/springframework/context/config/spring-context-3.0.xsd
- http://www.springframework.org/schema/context/spring-context-3.1.xsd=org/springframework/context/config/spring-context-3.1.xsd
- http://www.springframework.org/schema/context/spring-context-3.2.xsd=org/springframework/context/config/spring-context-3.2.xsd
- http://www.springframework.org/schema/context/spring-context-4.0.xsd=org/springframework/context/config/spring-context-4.0.xsd
- http://www.springframework.org/schema/context/spring-context-4.1.xsd=org/springframework/context/config/spring-context-4.1.xsd
- http://www.springframework.org/schema/context/spring-context.xsd=org/springframework/context/config/spring-context-4.1.xsd
- http://www.springframework.org/schema/jee/spring-jee-2.0.xsd=org/springframework/ejb/config/spring-jee-2.0.xsd
- http://www.springframework.org/schema/jee/spring-jee-2.5.xsd=org/springframework/ejb/config/spring-jee-2.5.xsd
- http://www.springframework.org/schema/jee/spring-jee-3.0.xsd=org/springframework/ejb/config/spring-jee-3.0.xsd
- http://www.springframework.org/schema/jee/spring-jee-3.1.xsd=org/springframework/ejb/config/spring-jee-3.1.xsd
- http://www.springframework.org/schema/jee/spring-jee-3.2.xsd=org/springframework/ejb/config/spring-jee-3.2.xsd
- http://www.springframework.org/schema/jee/spring-jee-4.0.xsd=org/springframework/ejb/config/spring-jee-4.0.xsd
- http://www.springframework.org/schema/jee/spring-jee-4.1.xsd=org/springframework/ejb/config/spring-jee-4.1.xsd
- http://www.springframework.org/schema/jee/spring-jee.xsd=org/springframework/ejb/config/spring-jee-4.1.xsd
- http://www.springframework.org/schema/lang/spring-lang-2.0.xsd=org/springframework/scripting/config/spring-lang-2.0.xsd
- http://www.springframework.org/schema/lang/spring-lang-2.5.xsd=org/springframework/scripting/config/spring-lang-2.5.xsd
- http://www.springframework.org/schema/lang/spring-lang-3.0.xsd=org/springframework/scripting/config/spring-lang-3.0.xsd
- http://www.springframework.org/schema/lang/spring-lang-3.1.xsd=org/springframework/scripting/config/spring-lang-3.1.xsd
- http://www.springframework.org/schema/lang/spring-lang-3.2.xsd=org/springframework/scripting/config/spring-lang-3.2.xsd
- http://www.springframework.org/schema/lang/spring-lang-4.0.xsd=org/springframework/scripting/config/spring-lang-4.0.xsd
- http://www.springframework.org/schema/lang/spring-lang-4.1.xsd=org/springframework/scripting/config/spring-lang-4.1.xsd
- http://www.springframework.org/schema/lang/spring-lang.xsd=org/springframework/scripting/config/spring-lang-4.1.xsd
- http://www.springframework.org/schema/task/spring-task-3.0.xsd=org/springframework/scheduling/config/spring-task-3.0.xsd
- http://www.springframework.org/schema/task/spring-task-3.1.xsd=org/springframework/scheduling/config/spring-task-3.1.xsd
- http://www.springframework.org/schema/task/spring-task-3.2.xsd=org/springframework/scheduling/config/spring-task-3.2.xsd
- http://www.springframework.org/schema/task/spring-task-4.0.xsd=org/springframework/scheduling/config/spring-task-4.0.xsd
- http://www.springframework.org/schema/task/spring-task-4.1.xsd=org/springframework/scheduling/config/spring-task-4.1.xsd
- http://www.springframework.org/schema/task/spring-task.xsd=org/springframework/scheduling/config/spring-task-4.1.xsd
- http://www.springframework.org/schema/cache/spring-cache-3.1.xsd=org/springframework/cache/config/spring-cache-3.1.xsd
- http://www.springframework.org/schema/cache/spring-cache-3.2.xsd=org/springframework/cache/config/spring-cache-3.2.xsd
- http://www.springframework.org/schema/cache/spring-cache-4.0.xsd=org/springframework/cache/config/spring-cache-4.0.xsd
- http://www.springframework.org/schema/cache/spring-cache-4.1.xsd=org/springframework/cache/config/spring-cache-4.1.xsd
- http://www.springframework.org/schema/cache/spring-cache.xsd=org/springframework/cache/config/spring-cache-4.1.xsd
从上述xml文档中可以看出,当没有配置版本号时,使用的即当前版本的xml schema文档。
- http://www.springframework.org/schema/context/spring-context.xsd=org/springframework/context/config/spring-context-4.1.xsd
上述即为对spring配置文档中的xml 文档验证的一部分说明,也是我在学习过程中所忽略的部分