我正在使用JPA，Hibernate和Sl4j開(kāi)發(fā)應(yīng)用程序。我不能讓sl4j記錄sql語(yǔ)句。這是我的代碼：persistence.xml<persistence-unit name="timeoffcore.persistence.unit">    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>    <properties>        <property name="hibernate.hbm2ddl.auto" value="create"/>        <property name="show_sql" value="true"/>    </properties></persistence-unit>log4j.properties# Direct log messages to a log filelog4j.appender.file=org.apache.log4j.RollingFileAppenderlog4j.appender.file.File=timeoff.loglog4j.appender.file.MaxFileSize=1MBlog4j.appender.file.MaxBackupIndex=1log4j.appender.file.layout=org.apache.log4j.PatternLayoutlog4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p %c{1}:%L - %m%n# Direct log messages to stdoutlog4j.appender.stdout=org.apache.log4j.ConsoleAppenderlog4j.appender.stdout.Target=System.outlog4j.appender.stdout.layout=org.apache.log4j.PatternLayoutlog4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p %c{1}:%L - %m%n# Root logger optionlog4j.rootLogger=INFO, file, stdout但是日志中沒(méi)有sql語(yǔ)句。既不在控制臺(tái)中，也不在文件中。