显示目录

Miscellaneous

RequestMapping

Since introduction of RequestMappingHandlerMapping and RequestMappingHandlerAdapter in Spring 3.1 the distinction is even simpler: RequestMappingHandlerMapping finds the appropriate handler method for the given request. RequestMappingHandlerAdapter executes this method, providing it with all the arguments.

mvc:view-controller

有很多静态页面,里没有动态的内容,如果写 Controller 去做映射的话又感觉很麻烦,都是体力活,没什么意思,这时可以用 mvc:view-controller 进行映射达到相同的效果而又不需要写 Controller。

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<!-- result.htm 是 View 的名字 -->
<mvc:view-controller path="/xtuer" view-name="result.htm"/>

访问 http://localhost/xtuer,则 View Resolver 访问的是 /WEB-INF/view/ftl/result.htm

Import Resource

把 Spring 的 Bean Configuration File 根据模块分散到不同的文件里,便于管理。
例如把上面提到的 mvc:view-controller,把所有静态文件的映射都放到 spring-static.xml 里,在 SpringMVC 主配置文件 spring-mvc.xml import spring-static.xml

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<?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:mvc="http://www.springframework.org/schema/mvc"
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">
...
<import resource="classpath:spring-static.xml"/> <!--位置随意-->
...
</beans>
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<!-- 文件名: spring-static.xml -->
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">
...
<mvc:view-controller path="/xtuer" view-name="result.htm"/>
...
</beans>

PropertyPlaceholderConfigurer

目的:在 properties 文件里定义一些属性,在 spring 的配置文件里用 ${propertyName} 的方式访问属性值,使用 PropertyPlaceholderConfigurer 加载 properties 文件。

数据源的配置:

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
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">
...
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/test?useUnicode=true&amp;characterEncoding=UTF-8" />
<property name="username" value="root" />
<property name="password" value="root" />
</bean>
...
</beans>

上面的 Spring 配置对于维护人员来说看起来很可能有困难,有太多他们不需要关心的东西干扰,他们实际关心的只是 driverClassName, url, username, password 等的内容,至于 Spring 配置相关的细节不需要知道。把他们提取到 properties 文件里,就是一些简单的 key/value,维护起来很方便,于是 Spring 的配置如下:

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
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">
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
</beans>

Spring 会自动的把 ${jdbc.driverClassName} 替换为 com.mysql.jdbc.Driver,等等。

database.properties 内容如下:

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jdbc.driverClassName=com.mysql.jdbc.Driver
# 在 xml 里 & 要用 &amp; 表示,在 properties 文件里就直接用 &
jdbc.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8
jdbc.username=root
jdbc.password=root

修改数据源配置时只需要修改 database.properties 文件,这样就简单很多了,不需要了解 Spring 的配置信息。

使用 PropertyPlaceholderConfigurer 加载 properties 文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
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">
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:database.properties</value>
</property>
</bean>
</beans>

加载多个 properties 文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
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">
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:database1.properties</value>
<value>classpath:database2.properties</value>
</list>
</property>
</bean>
</beans>

使用 context:property-placeholder 简化 PropertyPlaceholderConfigurer

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<?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"
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">
<context:property-placeholder location="classpath:database1.properties" ignore-unresolvable="true"/>
<context:property-placeholder location="classpath:database2.properties" ignore-unresolvable="true"/>
<!--推荐使用下面这种方式: 一个项目(可有多模块)或一个系统的配置应该放在一起,不宜分散-->
<context:property-placeholder location="classpath*:conf/conf*.properties"/>
</beans>