Use of the PropertyPlaceholder Configurer class in Spring

Hello, everyone!

This post will share with you the use of the PropertyPlaceholder configured class in spring.

This class is used to parse Java Properties property file values and provide alternative use of property values during spring configuration. Here are three common ways to use it.

1. Basic methods of use:

Spring-config.xml

<bean id="propertyConfigurer" class="org.spring framework.beans.factory.config.PropertyPlaceholder Configurer">
<property name="location">
<value>classpath:/spring/include/dbQuery.properties</value>
</property>
</bean>

Classpath refers to file writing in the SRC directory.

2. When multiple Properties files exist, configuration requires locations:

Spring-config.xml

<bean id="propertyConfigurer" class="org.spring framework.beans.factory.config.PropertyPlaceholder Configurer">
<property name="locations">
<list>
<value>classpath:/spring/include/jdbc-parms.properties</value>
<value>classpath:/spring/include/base-config.properties</value>
</list>
</property>
</bean>

3. Next, we need to use multiple Property Placeholder Configurers to decentralize the configuration so as to integrate multiple decentralized Proerties files under multiple projects. The configuration is as follows

Xml code

<bean id="propertyConfigurerForProject1" class="org.spring framework.beans.factory.config.Property Placeholder Configurer">
<property name="order" value="1"/>
<property name="ignoreUnresolvable Placeholders" value="true"/>
<property name="location">
<value>classpath:/spring/include/dbQuery.properties</value>
</property>
</bean>

Xml code

<bean id="propertyConfigurerForProject2" class="org.spring framework.beans.factory.config.Property Placeholder Configurer">
<property name="order" value="2"/>
<property name="ignoreUnresolvable Placeholders" value="true"/>
<property name="locations">
<list>
<value>classpath:/spring/include/jdbc-parms.properties</value>
<value>classpath:/spring/include/base-config.properties</value>
</list>
</property>
</bean>

Where the order attribute represents its loading order, ignoreUnresolvable Placeholders need to be set to true for ignoreUnresolvable Placeholders to ignore unresolved Placeholders, if multiple Property Placeholder Configurers are configured.

Usage in Manager code:

In the configuration of controller, some configuration files configure database user password and so on. In spring loading stage, the configuration file will be read and connected to the database. The configuration of database connection is as follows:

In persistence-context.xml, the configuration is as follows:

<! - Persistence context for Hadoop OM Model Setup - >
<bean id="omDataSource" class="com.huawei.hadoop.om.controller.persistence.MyDataSource" destroy-method="close">
<property name="driverClassName" value="${database.driverClassName}"/>
<property name="url" value="${database.url}"/>
<property name="username" value="${database.username}"/>
<property name="password" value="${database.password}"/>
<property name="validation Query" value="select 1"/>
<property name="maxActive" value="60"/>
</bean>

Among them, ${database.url}, ${database.username} and ${database.password} are all values obtained by parsing the value of the Java Properties property file. The configuration of properties is as follows:

In the controller-context.xml file, the following properties are configured:

Global Property Placement Holders

<bean
Class= "org. spring framework. beans. factory. config. Property Placeholder Configurer">
<property name="ignoreUnresolvable Placeholders" value="true"/>
<property name="locations">
<list>
< value > controller-private. properties </value> <! - - for internal purpose only - > <
<value>controller.properties</value>
<value>license.properties</value>
</list>
</property>
</bean>

Several of the Yellow Icon files, the property files loaded during spring loading, in which key-value pairs can be applied in other configurations, such as ${database.url}, ${database.username} and ${database.password} are configuration items in controller.properties file.

#\\\\\\\\\\\\\\\\\\\\
Database.url = jdbc: postgresql://127.0.0.1:<pg-port>/<db-name>
#\\\\\\\\\\\\\\\\\\\\
# Schema authentication.
#\\\\\\\\\\\\\\\\\\\\
Database. username = < DATABASE_USERNAME >
Database.password=<DATABASE_PASSWORD>

This is the second of the three uses described above.