Ajax发送请求放到Servlet，Servlet读取数据库返回json给Ajax。

前端

$("#btn").on("click",function(){  
    sqlStatement = document.getElementById("sqlStatement").value;
    $.ajax({
        type: "GET",
        url : "DemoServlet",
        dataType:"text",
        async: false,
        data:{sql: sqlStatement, pCount:pageCount},
        success: function(resultData){
            jObject = JSON.parse(resultData);
            document.getElementById("result").innerHTML = jObject.table;
        },
        error:function(xhr, status, errMsg){
            alert("Data transmission failed!");
        }
    });
});

后台:返回有个table给前台

import java.io.IOException;
import java.io.PrintWriter;

import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.ResultSet;

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

import net.sf.json.JSONObject;

@SuppressWarnings("serial")
public class DemoServlet extends HttpServlet{
    public static int EACHPAGENUM = 20;
    public String sql = null;
    public String newSQL = null;
    public String pageCount = null;
    public Connection connection = null;  
    public Statement statement = null;  
    public ResultSet resultSet = null;
    public ConnectDB2 connectDB2 = null;
    public PrintWriter out = null;
    public StringBuffer strTable = null;;
    public JSONObject jObject = null;
    public int pageNum = 0;
    public int allCount = 0;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        response.setHeader("Access-Control-Allow-Origin", "*");
        
        // Get SQL form ajax
        sql = request.getParameter("sql");
        newSQL = sql.replace("\"", "'");
        pageCount = request.getParameter("pCount");
        System.out.println("pCount = " + pageCount);
        System.out.println(newSQL);
        
        //Set up connection to DB2
        connectDB2 = new ConnectDB2();  
        connection = connectDB2.getConnection();
        PrintWriter out = response.getWriter();
         
        try {
            statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
            resultSet = statement.executeQuery(newSQL);
            
            ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
            
            //Get col name
            //out.println("<table border='1' width='100%'><tr>");
            strTable = new StringBuffer();
            strTable.append("<table border='1' width='100%' height='240px'><tr>");
            for (int i = 1;i <= resultSetMetaData.getColumnCount();i++) {
            //    out.println("<th>" + resultSetMetaData.getColumnName(i) + "</th>");
                strTable.append( "<th>" + resultSetMetaData.getColumnName(i) + "</th>");
            }
            strTable.append("</tr>");
            //System.out.println("strTable = " + strTable);
            
            pageNum = 0;
            resultSet.last();
            allCount = resultSet.getRow();
            if(resultSet.getRow() % 20 == 0) {
                pageNum = resultSet.getRow() / 20;
            }else {
                pageNum = resultSet.getRow() / 20 + 1;
            }
        
            System.out.println("pageNum = " + pageNum);
            if(Integer.parseInt(pageCount) <= pageNum) {
                resultSet.absolute(EACHPAGENUM * (Integer.parseInt(pageCount)-1) + 1);
                for(int j = 0;j < 20;j++){      
                    strTable.append("<tr>");
                    for (int i = 1;i <= resultSetMetaData.getColumnCount();i++) {    
                        //    out.println("<td>" + resultSet.getString(i) + "</td>");
                        strTable.append("<td>" + resultSet.getString(i) + "</td>");                        
                    }
                    strTable.append("</tr>");                    
                    //当cursor读取到最后一条record的时候
                    if(resultSet.getRow() == allCount) {
                        //打印剩余的空白cell
                        //for(int k = j;k < 20 - j;k++) {
                        //    strTable.append("<tr>");
                        //    for (int i = 1;i <= resultSetMetaData.getColumnCount();i++) {
                        //        strTable.append("<td></td>");
                        //    }
                        //    strTable.append("<tr>");
                        //}
                        break; //跳出循环20次的这层循环
                    }
                    resultSet.next();
                }
            }
            strTable.append("</table>");
            System.out.println(strTable); 
            
        } catch (Exception e) {
            // TODO: handle exception
            System.out.println(e);
        }
 
        jObject = new JSONObject();
        jObject.put("table", strTable.toString());
        jObject.put("pageNum", pageNum);
        out.write(jObject.toString());
        out.flush();
        out.close();
    }
}