分页显示数据库数据

数据分页显示作为网站显示数据的必备需求之一，每个程序猿都应该懂得如何将获取到的数据进行分页后展示。我今天要分享的不是简单的分页显示数据，而是将获取到的数据转换成JSON格式。如果想要的数据复杂的话，就需要HashMap嵌套ArrayList，ArrayList嵌套HashMap等。具体情况具体分析，我今天用到的就是HashMap嵌套ArrayList，ArrayList再嵌套HashMap。

获取的初始化数据：
{total=35, data=[{school=南京邮电学院, married=0, email=null, age=25, name=张鹏楠},{school=南京邮电学院, married=0,email=xucc198712@qq.com, age=27, name=徐承承},{school=宁波工程大学, married=0,email=xzz@163.com,
age=25, name=谢忠哲}],avgAge=27.2857}
格式化以后的数据：
{"total":35, "data":[{"school":"南京邮电学院","married":0,"email":null,"age":25,"name":"张鹏楠},{"school":"南京邮电学院","married":0,"email":"xucc198712@qq.com","age":27,"name":"徐承承},{"school":"宁波工程大学","married":0,"email":"xzz@163.com","age":25,"name":"谢忠哲}],"avgAge":27.2857}

分页展示的效果也就显示了，只给出具体的代码实现吧，还望参考：

<span style="font-size:14px;">import java.sql.Clob;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class TestDB {
	public static String driver = "com.mysql.jdbc.Driver";
	public static String url = "jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=GBK";
	public static String user = "root";
	public static String pwd = "root";
	/**
	 * 
	 * @param index			页码
	 * @param size			每页的数据量
	 * @return				返回当前页的数据
	 * @throws Exception
	 */
	public HashMap SearchEmployees(int index, int size, String sortField, String sortOrder) throws Exception
    {
    	String sql = "SQL语句";
    	//存储总的数据
        ArrayList dataAll = DBSelect(sql);
        
        //存储当前页要展示的数据
        ArrayList data = new ArrayList();
        
        int start = index * size, end = start + size;
        for (int i = 0, l = dataAll.size(); i < l; i++)
        {
            HashMap record = (HashMap)dataAll.get(i);
            if (record == null) continue;
            if (start <= i && i < end)
            {
                data.add(record);
            }
        }

        HashMap result = new HashMap();
        result.put("data", data);
        result.put("total", dataAll.size());

        return result;
    }
	/**
	 * 
	 * @param sql			sql语句
	 * @return				sql结果集
	 * @throws Exception
	 */
	public ArrayList DBSelect(String sql) throws Exception{
    	Connection conn = getConn();		
		Statement stmt = conn.createStatement();
    	
        ResultSet rst = stmt.executeQuery(sql);	
        
		ArrayList list = ResultSetToList(rst);
		
		rst.close();
		stmt.close();
		conn.close();
		
        return list;
	}
	
	private Connection getConn() throws Exception{		
		Class.forName(driver).newInstance();
		Connection conn = null;
		if(user == null || user.equals("")){
			conn = java.sql.DriverManager.getConnection(url);
		}else{
			conn = java.sql.DriverManager.getConnection(url, user, pwd);
		}
			
		return conn;
	}	
	/**
	 * 	将ResultSet查询到的结果集以“列名”：“数据”的形式保存到ArrayList数组中
	 * 
	 * @param rs			sql查询结果集
	 * @return				ArrayList
	 * @throws Exception
	 */
	private static ArrayList ResultSetToList(ResultSet   rs) throws Exception{    	
    	ResultSetMetaData md = rs.getMetaData();
    	int columnCount = md.getColumnCount();
    	ArrayList list = new ArrayList();
    	Map rowData;
    	while(rs.next()){
	    	rowData = new HashMap(columnCount);
	    	for(int i = 1; i <= columnCount; i++)   {	 	    		
	    		Object v = rs.getObject(i);	    		
	    		
	    		if(v != null && (v.getClass() == Date.class || v.getClass() == java.sql.Date.class)){
	    			Timestamp ts= rs.getTimestamp(i);
	    			v = new java.util.Date(ts.getTime());
	    			//v = ts;
	    		}
	    		rowData.put(md.getColumnName(i),   v);
	    	}
	    	list.add(rowData);	    	
    	}
    	return list;
	} 	
}</span><span style="font-size:18px;">
</span>

得到的Result即可以转化为JSON格式，具体的转化过程忽略……如有需要再补充说明，谢谢。