JDBC数据库相关

1、JDBCUTILS

package com.helper.Utlis;

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.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class JdbcUtils {

    // 数据库的用户名
    private final String USERNAME = "root";
    // 数据库的密码
    private final String PASSWORD = "fclbri";
    // 数据库的驱动信息,记住mysql-connector-java.jar-->Build PAth
    private final String DRIVER = "com.mysql.jdbc.Driver";
    // 访问数据库的地址，为什么一定是3306？？
    private final String URL = "jdbc:mysql://localhost:3306/ClassHelper?seUnicode=true&characterEncoding=UTF-8";
    // 数据库的连接
    private Connection connection;
    // 执行sql语句的对象
    private PreparedStatement pstmt;
    // 查询返回的数据集
    private ResultSet resultSet;
    //
    private Statement stmt;

    public JdbcUtils() {
        // 加载JDBC驱动程序,创建JdbcUtils对象时会执行
        try {
            Class.forName(DRIVER);// 加载
            System.out.println("数据库驱动加载成功!");
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();

        }
    }

    // 建立数据库连接
    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
            e.printStackTrace();
        }
        return connection;
    }

    public boolean deleteByBatch(String[] sql) throws SQLException {
        boolean flag = false;
        stmt = connection.createStatement();
        if (sql != null) {
            for (int i = 0; i < sql.length; i++) {
                stmt.addBatch(sql[i]);
            }
        }
        int[] count = stmt.executeBatch();
        if (count != null) {
            flag = true;
        }
        return flag;
    }

    /**
     * PrepareStatement用于执行动态的SQL语句 对表进行操作：添加，修改，删除
     * 
     * @param sql
     * @param params
     * @return
     * @throws SQLException
     */
    public boolean updateByPreparedStatement(String sql, List<Object> params)
            throws SQLException {
        boolean flag = false;
        int result = -1;// 表示执行sql语句时影响数据库的行数
        pstmt = connection.prepareStatement(sql);
        int index = 1;
        // 判断集合不为空的标准条件语句
        if (params != null && !params.isEmpty()) {
            for (int i = 0; i < params.size(); i++) {
                pstmt.setObject(index++, params.get(i));
            }
        }
        result = pstmt.executeUpdate();// 执行sql语句+返回执行后影响数据库的行数
        flag = result > 0 ? true : false;
        return flag;
    }

    /**
     * 查询并返回单条记录
     */
    public Map<String, Object> findSimpleResult(String sql, List<Object> params)
            throws SQLException {
        Map<String, Object> map = new HashMap<String, Object>();
        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();// 查询结果
        ResultSetMetaData metaData = resultSet.getMetaData();
        int col_len = metaData.getColumnCount();// 获得列的数量
        while (resultSet.next()) // 如果有下一条记录
        {
            for (int i = 0; i < col_len; i++) {
                String cols_name = metaData.getColumnName(i + 1);// 获得列的名称
                Object cols_value = resultSet.getObject(cols_name);
                if (cols_value == null) {
                    cols_value = "";
                }
                map.put(cols_name, cols_value);
            }
        }
        return map;
    }

    /**
     * 查询并返回多条记录
     * 
     * @param sql
     * @param params
     * @return
     * @throws SQLException
     */
    public List<Map<String, Object>> findMoreResult(String sql,
            List<Object> params) throws SQLException {
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        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 = resultSet.getMetaData();
        int cols_len = metaData.getColumnCount();
        while (resultSet.next()) {
            Map<String, Object> map = new HashMap<String, Object>();
            for (int i = 0; i < cols_len; i++) {
                String cols_name = metaData.getColumnName(i + 1);// 获得列的名称
                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
     * 
     * @param sql
     * @param params
     * @param cls
     *            T表示泛型,这个类必须与查询的结果的所有列的字段一一对应，不多不少，类型相同
     * @return
     * @throws Exception
     */
    public <T> T findSimpleRefResult(String sql, List<Object> params,
            Class<T> cls) throws Exception {
        T resultObject = null;
        int index = 1;
        pstmt = connection.prepareStatement(sql);
        // params数组依次给？赋值
        if (params != null && !params.isEmpty()) {
            for (int i = 0; i < params.size(); i++) {
                pstmt.setObject(index++, params.get(i));
            }
        }
        resultSet = pstmt.executeQuery();// 查询的结果
        ResultSetMetaData metaData = resultSet.getMetaData();
        int cols_len = metaData.getColumnCount();
        while (resultSet.next()) {
            // ͨ通过反射机制创建一个实例
            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 = "";
                }
                Field field = cls.getDeclaredField(cols_name);
                field.setAccessible(true);// 打开javabean的访问private 权限
                field.set(resultObject, cols_value);
            }
        }
        return resultObject;
    }

    /**
     * 返回多条记录 JDBC的封装可以使用反射机制来封装 T表示泛型
     */
    public <T> List<T> findMoreRefResult(String sql, List<Object> params,
            Class<T> cls) throws Exception {
        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 = 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;
    }

    // 关闭数据库的连接
    public void releaseConn() {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (stmt != null) {
            try {
                stmt.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();
            }
        }
    }

}

2、增删查改

增加

    @Override
    public boolean addNotice(Notice notice) {
        String sql = "insert into tb_notice (title,body,exigency,stuid,    timestamp) values (?,?,?,?,?)";
        List<Object> params = new ArrayList<Object>();
        params.add(notice.getTitle());
        params.add(notice.getBody());
        params.add(notice.isExigency());
        params.add(notice.getStuid());
        Timestamp ts = new Timestamp(System.currentTimeMillis());
        params.add(ts.toString());
        boolean flag = false;
        jdbcUtils.getConnection();
        try {
            flag = jdbcUtils.updateByPreparedStatement(sql, params);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return flag;
    }

删除

    @Override
    public boolean delNotice(String id) {
        // TODO Auto-generated method stub
        jdbcUtils.getConnection();
        boolean flag=false;
        String[] sql={"delete from tb_notice where id='" + id + "'"};
        try {
            flag=jdbcUtils.deleteByBatch(sql);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return flag;
    }

查找

    public List<DkRecord> listById(String openid) {
        // TODO Auto-generated method stub
        String sql = "select id,tb_daka.openid,tb_userinfo.nickname,time,content from tb_daka,tb_userinfo where tb_daka.openid=tb_userinfo.openid  and tb_daka.openid=? order by time desc";
        jdbcUtils.getConnection();
        List<DkRecord> list = null;
        List<Object> params=new ArrayList<Object>();
        params.add(openid);
        try {
            list = jdbcUtils.findMoreRefResult(sql, params, DkRecord.class);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return list;
    }

更改

    @Override
    public boolean editqq(String stuid, String qq) {
        
        List<Object> params=new ArrayList<Object>();
        params.add(qq);
        params.add(stuid);
        boolean flag = false;
        jdbcUtils.getConnection();
        String sql="update tb_student set qq=? where stuid=?";
        try {
            flag=jdbcUtils.updateByPreparedStatement(sql, params);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return flag;
    }

Done！