java - ORA-01858 insert log in database -

i writing class in application insert logs oracle database. have used log4j. made these configurations:

<appender name="db" class="org.apache.log4j.jdbc.jdbcappender">    <param name="url" value="jdbc:oracle:thin:@10.60.2.8:1521:dbname"/>    <param name="driver" value="oracle.jdbc.driver.oracledriver"/>    <param name="user" value="test"/>    <param name="password" value="test"/>     <layout class="org.apache.log4j.patternlayout">     <param name="conversionpattern" value="insert log_overloadrequest values('%x{today}','%x {currentrequesturi}','%x {username}','%x {uri}','%x {method}','%x {cpuload}','%x {timespent}','%x {lastcpuload}','%x {firstfreememory}','%x {lastfreememory}','%x {appid}','%x {sessionid}')"/> </layout> </appender> 

here codes in class:

private logger overloadrequestdb=logger.getlogger("log4j.rootlogger");  timestamp today = new timestamp(system.currenttimemillis());                 mdc.put("today", today);                 mdc.put("currentrequesturi", currentrequesturi);                 mdc.put("username", "test");                 mdc.put("uri", currentrequesturi);                 mdc.put("method", "test");                 mdc.put("cpuload",1234);                 mdc.put("timespent", 1234);                 mdc.put("lastcpuload", 123);                 mdc.put("firstfreememory", 123);                 mdc.put("lastfreememory", 123);                 mdc.put("appid", 1);                 mdc.put("sessionid","123");  overloadrequestdb.debug("test");                 overloadrequestdb.info("test"); 

when run application face error: ora-01858: non-numeric character found numeric expected

i think ths related date, did don't know problem is.