PLS-00103: 出现符号 ","在需要下列之一时

PLS-00103: 出现符号 ","在需要下列之一时

存储过程出下：（ 注：我使用的是oracle 10g)
 

procedure aaaa(i_vc2mob       in   varchar2 ,  -- 用户号码
                         i_NUMSVCID     in  PLS_INTEGER  default   null ,  -- SERVICECODEID
                         i_prodid       in  PLS_INTEGER  default   null ,  -- 产品ID
                         i_disordsrc    in  PLS_INTEGER,  -- 退定来源
                         i_disordsrcid  in   NUMBER ,  -- 退定来源ID
                         i_datdisorder  in  date  default  sysdate,  -- 退定时间
                         o_prodid      out PLS_INTEGER,  -- 返回产品ID 
                         o_level       out PLS_INTEGER,  -- 返回用户级别
                         o_flag        out PLS_INTEGER  -- 返回状态
                         )  is

在java中调用正确调用方法：
{ call aaaa('13472622059',1,1,21,4712032059528901,'',?,?,?)}

如果这样写
{ call aaaa('13472622059',1,1,21,4712032059528901,,?,?,?)}
就报如下异常：
java.sql.SQLException: ORA-06550: 第 1 行, 第 67 列:
PLS-00103: 出现符号 ","在需要下列之一时：
 ( - + case mod new not null
   others <an identifier> <a double-quoted delimited-identifier>
   <a bind variable> avg count current exists max min prior sql
   stddev sum variance execute forall merge time timestamp
   interval date
   <a string literal with character set specification>
   <a number> <a single-quoted SQL string> pipe
   <一个带有字符集说明的可带引号的字符串文字>
   <一个可带引号的 SQL 字符串>
符号 "null" 被替换为 "," 后继续。

    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:331)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:288)
    at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:743)
    at oracle.jdbc.driver.T4CCallableStatement.doOall8(T4CCallableStatement.java:215)
    at oracle.jdbc.driver.T4CCallableStatement.executeForRows(T4CCallableStatement.java:954)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1168)
    at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3285)
    at oracle.jdbc.driver.OraclePreparedStatement.execute(OraclePreparedStatement.java:3390)
    at oracle.jdbc.driver.OracleCallableStatement.execute(OracleCallableStatement.java:4223)
    at com.pub.comm.db.DBDeal.callProcedures2(DBDeal.java:36)
    at com.pub.comm.db.Test.<init>(Test.java:15)
    at com.pub.comm.db.Test.main(Test.java:29)