JDBC深度封装的工具类，jdbc封装工具类,首先介绍一下Dbutil

JDBC深度封装的工具类，jdbc封装工具类,首先介绍一下Dbutil

首先介绍一下Dbutils： CommonDbutils是操作数据库的组件，对传统操作数据库的类进行二次封装，可以把结果集转化成List。补充一下，传统操作数据库的类指的是JDBC（javadatabaseconnection：java数据库连接，java的数据库操作的基础API。）。DBUtils是java编程中的数据库操作实用工具，小巧简单实用。有兴趣的话可以到官网下载：http://commons.apache.org/dbutils/ 下面的工具包正是符合了CommonDbutils的思想```javapackage com.util;

import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.lang.reflect.Field;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Properties;

public class JdbcUtils{

// 表示定义数据库的用户名private final String USERNAME = "root";// 定义数据库的密码private final String PASSWORD = "admin";// 定义数据库的驱动信息private final String DRIVER = "com.mysql.jdbc.Driver";// 定义访问数据库的地址private final String URL = "jdbc:mysql://localhost:3306/mydb";// 定义数据库的链接private Connection connection;// 定义sql语句的执行对象private PreparedStatement pstmt;// 定义查询返回的结果集合private ResultSet resultSet;public JdbcUtils(){    try    {        Class.forName(DRIVER);        System.out.println("注册驱动成功!!");    }    catch (Exception e)    {        // TODO: handle exception    }}// 定义获得数据库的链接public Connection getConnection(){    try    {        connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);        System.out.println("数据库连接成功");    }    catch (Exception e)    {        // TODO: handle exception    }    return connection;}public boolean updateByPreparedStatement(String sql, Listparams)        throws SQLException{    boolean flag = false;    int result = -1;// 表示当用户执行添加删除和修改的时候所影响数据库的行数    pstmt = connection.prepareStatement(sql);    int index = 1;    // 填充sql语句中的占位符    if (params != null &amp;&amp; !params.isEmpty())    {        for (int i = 0; i < params.size(); i++)        {            pstmt.setObject(index++, params.get(i));        }    }    result = pstmt.executeUpdate();    flag = result > 0 ? true : false;    return flag;}public Map findSimpleResult(String sql, Listparams)        throws SQLException{    Map map = new HashMap();    int index = 1;    pstmt = connection.prepareStatement(sql);    if (params != null &amp;&amp; !params.isEmpty())    {        for (int i = 0; i < params.size(); i++)        {            pstmt.setObject(index++, params.get(i));        }    }    resultSet = pstmt.executeQuery();// 返回查询结果    // 获取此 ResultSet 对象的列的编号、类型和属性。    ResultSetMetaData metaData = resultSet.getMetaData();    int col_len = metaData.getColumnCount();// 获取列的长度    while (resultSet.next())// 获得列的名称    {        for (int i = 0; i < col_len; i++)        {            String cols_name = metaData.getColumnName(i + 1);            Object cols_value = resultSet.getObject(cols_name);            if (cols_value == null)// 列的值没有时，设置列值为“”            {                cols_value = "";            }            map.put(cols_name, cols_value);        }    }    return map;}public List> findMoreResult(String sql,        Listparams) throws SQLException{    List> list = new ArrayList>();    int index = 1;    pstmt = connection.prepareStatement(sql);    if (params != null &amp;&amp; !params.isEmpty())    {        for (int i = 0; i < params.size(); i++)        {            pstmt.setObject(index++, params.get(i));        }    }    resultSet = pstmt.executeQuery();    ResultSetMetaData metaData = resultSet.getMetaData();    int cols_len = metaData.getColumnCount();    while (resultSet.next())    {        Map map = new HashMap();        for (int i = 0; i < cols_len; i++)        {            String cols_name = metaData.getColumnName(i + 1);            Object cols_value = resultSet.getObject(cols_name);            if (cols_value == null)            {                cols_value = "";            }            map.put(cols_name, cols_value);        }        list.add(map);    }    return list;}public T findSimpleRefResult(String sql, Listparams,        Class cls) throws Exception{    T resultObject = null;    int index = 1;    pstmt = connection.prepareStatement(sql);    if (params != null &amp;&amp; !params.isEmpty())    {        for (int i = 0; i < params.size(); i++)        {            pstmt.setObject(index++, params.get(i));        }    }    resultSet = pstmt.executeQuery();    ResultSetMetaData metaData = resultSet.getMetaData();    int cols_len = metaData.getColumnCount();    while (resultSet.next())    {        // 通过反射机制创建实例        resultObject = cls.newInstance();        for (int i = 0; i < cols_len; i++)        {            String cols_name = metaData.getColumnName(i + 1);            Object cols_value = resultSet.getObject(cols_name);            if (cols_value == null)            {                cols_value = "";            }            // 返回一个 Field 对象，该对象反映此 Class 对象所表示的类或接口的指定已声明字段。           Field field = cls.getDeclaredField(cols_name);            field.setAccessible(true);// 打开javabean的访问private权限            field.set(resultObject, cols_value);// 为resultObject对象的field的属性赋值        } //上面的两行红题字就是要求实体类中的属性名一定要和数据库中的字段名一定要严//格相同（包括大小写）,而oracle数据库中一般都是大写的，如何让oracle区分大小写，请看博///文：http://blog.sina.com.cn/s/blog_7ffb8dd501013xkq.html    }    return resultObject;}public List findMoreRefResult(String sql, Listparams,        Class cls) throws Exception{    List list = new ArrayList();    int index = 1;    pstmt = connection.prepareStatement(sql);    if (params != null &amp;&amp; !params.isEmpty())    {        for (int i = 0; i < params.size(); i++)        {            pstmt.setObject(index++, params.get(i));        }    }    resultSet = pstmt.executeQuery();    ResultSetMetaData metaData = resultSet.getMetaData();    int cols_len = metaData.getColumnCount();    while (resultSet.next())    {        T resultObject = cls.newInstance();        for (int i = 0; i < cols_len; i++)        {            String cols_name = metaData.getColumnName(i + 1);            Object cols_value = resultSet.getObject(cols_name);            if (cols_value == null)            {                cols_value = "";            }            Field field = cls.getDeclaredField(cols_name);            field.setAccessible(true);            field.set(resultObject, cols_value);        }        list.add(resultObject);    }    return list;}public void releaseConn(){    if (resultSet != null)    {        try        {            resultSet.close();        }        catch (SQLException e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    if (pstmt != null)    {        try        {            pstmt.close();        }        catch (SQLException e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    if (connection != null)    {        try        {            connection.close();        }        catch (SQLException e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}public static void writeProperties(String url, String user, String password){    Properties pro = new Properties();    FileOutputStream fileOut = null;    try    {        fileOut = new FileOutputStream("Config.ini");        pro.put("url", url);        pro.put("user", user);        pro.put("password", password);        pro.store(fileOut, "My Config");    }    catch (Exception e)    {        e.printStackTrace();    }    finally    {        try        {            if (fileOut != null)                fileOut.close();        }        catch (IOException e)        {            e.printStackTrace();        }    }}public static List readProperties(){    List list = new ArrayList();    Properties pro = new Properties();    FileInputStream fileIn = null;    try    {        fileIn = new FileInputStream("Config.ini");        pro.load(fileIn);        list.add(pro.getProperty("url"));        list.add(pro.getProperty("user"));        list.add(pro.getProperty("password"));    }    catch (Exception e)    {        e.printStackTrace();    }    finally    {        try        {            if (fileIn != null)                fileIn.close();        }        catch (IOException e)        {            e.printStackTrace();        }    }    return list;}public static void main(String[] args){    // TODO Auto-generated method stub    JdbcUtils jdbcUtils = new JdbcUtils();    jdbcUtils.getConnection();    // String sql = "insert into userinfo(username,pswd) values(?,?)";    // Listparams = new ArrayList();    // params.add("rose");    // params.add("123");    // try {    // boolean flag = jdbcUtils.updateByPreparedStatement(sql, params);    // System.out.println(flag);    // } catch (SQLException e) {    // // TODO Auto-generated catch block    // e.printStackTrace();    // }    String sql = "select * from userinfo ";    // Listparams = new ArrayList();    // params.add(1);}

}

```