Mysql,JDBC封装

1.完成对数据库的表的增删改的操作

2.查询返回单条记录

3.查询返回多行记录

4.可以使用反射机制来封装,查询单条记录

5.反射机制，查询多条记录

package myjdbc;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.sound.midi.MetaEventListener;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Field;
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.ResultSetMetaData;

import domain.UserInfo;

public class JdbcUtil {
    //表示数据库的用户名
    private final String USERNAME = "root";
    //表示数据库的密码
    private final String PASSWORD = "hang796413";
    //数据库的驱动信息
    private final String DRIVER     = "com.mysql.jdbc.Driver";
    //访问数据库的地址
    private final String URL = "jdbc:mysql://localhost:3306/gustomer";
    //定义数据库的链接
    private Connection connection;
    //定义sqk语句的执行对象
    private java.sql.PreparedStatement pstmt;
    //定义查询返回的结果集合
    private ResultSet resultSet;

    public JdbcUtil(){
        try {
            Class.forName(DRIVER);
            System.out.println("注册驱动成功");
            connection = (Connection) DriverManager.getConnection(URL,USERNAME,PASSWORD);
            System.out.println("链接成功");
        } catch (Exception e) {

        }
    }
    /*完成对数据库的表的增删改的操作
     *
     * @param sql
     * @param params
     * @retuen
     * @throws SQLException
     * */
    public boolean upderbypaerdstaemnet(String sql, List<Object>
            params)throws SQLException{
        boolean flag = false;
        int result = -1;//表示当用户执行增删改所影响数据库的行数
        pstmt = connection.prepareStatement(sql);

        int index = 1;
        if(params != null && !params.isEmpty()){
            for(int i = 0; i<params.size();i++){
                pstmt.setObject(index++, params.get(i));
            }
        }
        System.out.println(pstmt.toString());
        result = pstmt.executeUpdate();
        System.out.println(result);
        flag = result > 0 ? true : false;
        return flag;

    }
    /*查询返回单条记录
     * */
    public Map<String,Object> findSimpleResult(String sql, List<Object>
    params)throws SQLException{
        Map<String,Object> map = new HashMap<String,Object>();
        //组合SQL语句
        pstmt = connection.prepareStatement(sql);
        int index = 1;
        if(params != null && !params.isEmpty()){
            for(int i = 0; i<params.size();i++){
                pstmt.setObject(index++, params.get(i));
    }
}
        System.out.println(pstmt.toString());

        resultSet = pstmt.executeQuery();//返回查询结果
        //获取列的信息 -> metaData
        ResultSetMetaData metaData = (ResultSetMetaData) resultSet.getMetaData();
        int col_len = metaData.getColumnCount();//获得列的名称
       System.out.println(col_len);
       //如果还有其他列
        while(resultSet.next()){

            for(int i = 0; i<col_len;i++){
                //记录 名字和值
                 System.out.println("11112333332233332");
                 //i+1!!!!!!!!
                String cols_name = metaData.getColumnName(i+1);
                System.out.println(cols_name);
                Object cols_value =resultSet.getObject(cols_name);
            if( cols_value == null){
                cols_value = " ";
            }

            map.put(cols_name, cols_value);
            }
        }

        return map;
}
    /*
     * 查询返回多行记录
     * */
    public List<Map<String,Object>> findMoreResult(String sql, List<Object>
    params)throws SQLException{
        List<Map<String,Object>>  list = new ArrayList<Map<String,Object>>();
        pstmt = connection.prepareStatement(sql);
        int index = 1;
        if(params != null && !params.isEmpty()){

            for(int i = 0; i<params.size();i++){
                pstmt.setObject(index++, params.get(i));
    }
}
        System.out.println(pstmt.toString());
        resultSet = pstmt.executeQuery();//返回查询结果
        //获取列的信息 -> metaData
        ResultSetMetaData metaData = (ResultSetMetaData) resultSet.getMetaData();
        int col_len = metaData.getColumnCount();//获得列的名称
        while(resultSet.next()){
            //******多了这个地方****/
            Map<String,Object> map = new HashMap<String,Object>();
            for(int i = 0; i<col_len;i++){
                //记录 名字和值
                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;
    }
    //jdbc的封装可以使用反射机制来封装
    public <T> T findSimpleRefResult(String sql ,List<Object>params,
            Class<T> cls)throws SQLException, InstantiationException, IllegalAccessException, NoSuchFieldException, SecurityException {
        T resultObject = null;
        int index = 1;
        pstmt = connection.prepareStatement(sql);
        if(params != null && !params.isEmpty()){
            for(int i = 0; i<params.size();i++){
                pstmt.setObject(index++, params.get(i));
            }
        }
        resultSet = pstmt.executeQuery();
        ResultSetMetaData metaData =(ResultSetMetaData) resultSet.getMetaData();
        int cols_len = metaData.getColumnCount();
        while(resultSet.next()){
            //通过反射机制创建实例

            resultObject = cls.newInstance();
            //初始化
            for(int i = 0; i<cols_len;i++){
                //记录 名字和值

                String cols_name = metaData.getColumnName(i+1);
                Object cols_value =resultSet.getObject(cols_name);

            if( cols_value == null){
                cols_value = " ";
            }
            //获取javabean（UserInfo）对应列的属性
            java.lang.reflect.Field field = cls.getDeclaredField(cols_name);
            //打开javabea的访问私有权限
            field.setAccessible(true);
            //相对应的javabean进行赋值
            field.set(resultObject,cols_value);

        }
        }
                return resultObject;
    }
    /*
     * 通过反射机制访问数据库
     * */
    public <T> List <T> finMoreRefResult(String sql ,List<Object>params,
            Class<T> cls)throws SQLException, IllegalArgumentException, IllegalAccessException, NoSuchFieldException, SecurityException, InstantiationException{
        List <T> list = new ArrayList<T>();
        int index = 1;
        pstmt = connection.prepareStatement(sql);
        if(params != null && !params.isEmpty()){
            for(int i = 0; i<params.size();i++){
                pstmt.setObject(index++, params.get(i));
            }
        }
        resultSet = pstmt.executeQuery();
        ResultSetMetaData metaData =(ResultSetMetaData) resultSet.getMetaData();
        int cols_len = metaData.getColumnCount();
        while(resultSet.next()){
            //通过反射机制创建实例
            T resultObject = cls.newInstance();
            //初始化
            for(int i = 0; i<cols_len;i++){
                //记录 名字和值
                String cols_name = metaData.getColumnName(i+1);
                Object cols_value =resultSet.getObject(cols_name);
            if( cols_value == null){
                cols_value = " ";
            }
            //获取javabean（UserInfo）对应列的属性
            java.lang.reflect.Field field = cls.getDeclaredField(cols_name);
            //打开javabea的访问私有权限
            field.setAccessible(true);
            //相对应的javabean进行赋值
            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 main(String[] args){
        JdbcUtil jdbcUtil = new JdbcUtil();

//        String sql = "insert into userinfo(username,pswd) values(?,?)";
//        List<Object> params = new ArrayList<Object>();
//        params.add("rose");
//        params.add("123");
//        try {
//         boolean flag = jdbcUtil.upderbypaerdstaemnet(sql, params);
//         System.out.println(flag);
//        } catch (Exception e) {
//        }
        String sql ="select * from userinfo ";
        //查询单个
        //List<Object>params = new ArrayList<Object>();
        //params.add(1);//id为1的记录
        try {
            List<UserInfo> list= jdbcUtil.finMoreRefResult(sql,null,UserInfo.class);
            System.out.println(list);
        } catch (Exception e) {

        }finally {
            jdbcUtil.releaseConn();
        }
    }
}

package domain;

import java.io.Serializable;

public class UserInfo implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private int id;
    private String username;
    private String pswd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "UserInfo [id=" + id + ", username=" + username + ", pswd=" + pswd + "]";
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPswd() {
        return pswd;
    }

    public void setPswd(String pswd) {
        this.pswd = pswd;
    }

    public UserInfo(){

    }
}