Mysql创建存储过程：

create procedure s_add(in a int, in b int, out sum int)  
begin  
    set sum = a + b;  
end

之后这是Java代码

package ch04.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Types;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CstmtExample extends HttpServlet{
    private String url;
    private String user;
    private String password;
    public void init() throws ServletException {
        ServletContext sc = getServletContext();
        String driverClass = sc.getInitParameter("driverClass");
        url = sc.getInitParameter("url");
        user = sc.getInitParameter("user");
        password = sc.getInitParameter("password");
        try {
            Class.forName(driverClass);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }        
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Connection conn = null;
        CallableStatement cstmt = null;
        try {
            conn = DriverManager.getConnection(url, user, password);
            cstmt = conn.prepareCall("{call s_add(?, ?, ?)}");
            cstmt.setInt(1, 5);
            cstmt.setInt('b', 6);
            cstmt.registerOutParameter(3, Types.INTEGER);
            cstmt.execute();
            int ret = cstmt.getInt(3);
            PrintWriter out = resp.getWriter();
            out.println(ret);
            out.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }    
    }
}

连接没问题，就是对于控制台输出的报错不知道怎么改？

java.sql.SQLException: Parameter index out of range (98 > number of parameters, which is 3).
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:965)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:898)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:887)

这是控制台报错。