时间戳

首页 > 解决方案 > 在 spring applicationContext.xml 中访问系统属性时出错

java - 在 spring applicationContext.xml 中访问系统属性时出错

问题描述

我想将我的 db 文件位置设置为系统变量的一部分，该变量应在启动应用程序时提供。我想访问applicationContext.xml我尝试使用#{systemProperties['db.properties']}的这个系统属性applicationContext.xml.

我以以下两种方式定义了 propertyPlaceholderConfigurer bean，以两种不同的方式为属性“位置”指定值：

情况1 ＃：

<bean id="propertyPlaceholderConfigurer"
        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
        <property name="searchSystemEnvironment" value="true"/>
        <property name="locations">

             <value>file://"#{systemProperties['db.properties']}"</value>
        </property>
        <property name="ignoreResourceNotFound" value="true" />
         <property name="ignoreUnresolvablePlaceholders" value="true"/>
</bean>

数据源 bean #:

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" 
        destroy-method="close"> 
     <property name="driverClassName" value="org.postgresql.Driver"/> 
     <property name="url" value="${db.url}"/>
     <property name="username" value="${db.user}"/>
     <property name="password" value="${db.pwd}"/>
</bean>

案例2#：

<bean id="propertyPlaceholderConfigurer"
        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
        <property name="searchSystemEnvironment" value="true"/>
        <property name="locations">

            <value>file://${DB_CONF}/test/db.properties</value>
        </property>
        <property name="ignoreResourceNotFound" value="true" />
         <property name="ignoreUnresolvablePlaceholders" value="true"/>
</bean>

如果我在案例 2 中使用属性位置的值而不是 "#{systemProperties['db.properties']}" 应用程序可以正常工作。在案例 1 中，我尝试从与系统属性相同的位置访问相同的属性文件，但应用程序无法正常工作，错误如下：

堆栈跟踪

Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:235)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:171)
    at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:450)
    at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:450)
    ... 133 more
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot create JDBC driver of class 'org.postgresql.Driver' for connect URL '${db.url}'
    at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1452)
    at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
    at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
    at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:139)
    at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:380)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:228)
    ... 136 more
Caused by: java.sql.SQLException: No suitable driver
    at java.sql.DriverManager.getDriver(DriverManager.java:315)
    at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1437)

标签： javaspring

解决方案

我可以解决错误。罪魁祸首是双引号。使用 file://#{systemProperties['db.properties']} 而不是 file://"#{systemProperties['db.properties']}" 解决了这个问题。

推荐阅读