Java學習筆記（三）—— JDBC封裝

這裏提供使用Map返回當行記錄的封裝

public Map<String, Object> selectSimpleResult(String sql, List<Object> params)

和 返回List<Map<String,Object>> 返回多行記錄從而查詢多行記錄，這裏list代表多行記錄，每一行當中的都代表一個鍵值對，從而實現返回多行記錄

public List<Map<String, Object>> selectMoreResult(String sql, List<Object> params)

package jdbcTest;

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;

/**
 * 
 * @author chencong
 * @Time 2017年8月3日 上午9:37:00
 * @TODO 進行封裝jdbc方法的增刪改查 ， 同時提供反射機制封裝
 */
public class JDBCUtils {

    private static final String DRIVER_URL = "jdbc:sqlserver://localhost:1433;DataBaseName=mangerQQSys";
    private static final String DRIVER_NAME = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
    private static final String DB_USER = "sa";
    private static final String DB_PASSWORD = "123456";

    private Connection connection = null;
    private PreparedStatement preparedStatement = null;
    private ResultSet resultSet = null;

    public JDBCUtils() {
        try {
            Class.forName(DRIVER_NAME);
            System.out.println("連接成功！");
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    /**
     * 提供Connection的getConnection()方法獲得一個數據庫連接
     * 
     * @return 返回數據庫連接Connection
     */
    public Connection getConnection() {
        try {
            connection = DriverManager.getConnection(DRIVER_URL, DB_USER, DB_PASSWORD);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return connection;
    }

    /**
     * 增加、刪除、修改
     * <p>
     * sql = "select stuId , stuName form student where stuId = ?"
     * 此時的params中就爲這裏？的佔位符
     * 
     * @param sql
     *            將要執行的的sql語句
     * @param params
     *            sql語句中的參數
     * @return 返回是否執行成功
     * @throws SQLException
     *             拋出sql異常
     */
    public boolean updateByPreparedStatement(String sql, List<Object> params) throws SQLException {
        if (connection == null) {
            return false;
        }
        if (sql == null || params == null || params.isEmpty()) {
            return false;
        }
        int result = -1;
        boolean flag = false;
        int index = 1;
        preparedStatement = connection.prepareStatement(sql);
        // 遍歷參數列表
        for (int i = 0; i < params.size(); i++) {
            preparedStatement.setObject(index, params.get(i));
            index++;
        }
        result = preparedStatement.executeUpdate();
        flag = result > 0 ? true : false;
        return flag;
    }

    /**
     * 單條記錄查詢
     * 
     * @param sql
     *            將要執行的sql語句
     * @param params
     *            該條sql語句當中的參數列表
     * @return 返回單條記錄的map集合
     * @throws SQLException
     */
    public Map<String, Object> selectSimpleResult(String sql, List<Object> params) throws SQLException {
        if (connection == null) {
            return null;
        }
        if (sql == null || params == null || params.isEmpty()) {
            return null;
        }
        Map<String, Object> map = new HashMap<>();
        int index = 1;
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.size(); i++) {
            preparedStatement.setObject(index, params.get(i));
            index++;
        }
        // 返回查詢結果
        resultSet = preparedStatement.executeQuery();
        ResultSetMetaData metaData = resultSet.getMetaData();
        int col_length = metaData.getColumnCount();
        while (resultSet.next()) {
            for (int i = 0; i < col_length; i++) {
                String col_name = metaData.getColumnName(i + 1); // 列名從1開始
                Object col_value = resultSet.getObject(col_name); // 通過列名查詢該列的值
                if (col_value == null) {
                    col_value = "";
                }

                map.put(col_name, col_value);
            }
        }
        return map;
    }

    /**
     * 多行記錄查詢
     * 
     * @param sql
     * @param params
     * @return
     * @throws SQLException
     */
    public List<Map<String, Object>> selectMoreResult(String sql, List<Object> params) throws SQLException {
        if (connection == null) {
            return null;
        }
        if (sql == null || params == null || params.isEmpty()) {
            return null;
        }
        int index = 1;
        List<Map<String, Object>> list = new ArrayList<>();
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.size(); i++) {
            preparedStatement.setObject(index, params.get(i));
            index++;
        }
        resultSet = preparedStatement.executeQuery();
        ResultSetMetaData metaData = resultSet.getMetaData();
        int col_length = metaData.getColumnCount();
        while (resultSet.next()) {
            Map<String, Object> map = new HashMap<>();
            for (int i = 0; i < col_length; i++) {
                String col_name = metaData.getColumnName(i + 1);
                Object col_value = resultSet.getObject(col_name);
                if (col_value == null) {
                    col_value = "";
                }
                map.put(col_name, col_value);
            }
            list.add(map);
        }
        return list;
    }

    /**
     * 關閉數據庫連接
     * 
     * @param resultSet
     * @param statement
     * @param connection
     * @throws SQLException
     */
    public void closeAll(ResultSet resultSet, Statement statement, Connection connection) throws SQLException {
        if (resultSet != null) {
            resultSet.close();
        }
        if (connection != null) {
            connection.close();
        }
        if (statement != null) {
            statement.close();
        }
    }

    /**
     * 關閉連接
     * 
     * @param resultSet
     * @param statement
     * @throws SQLException
     */
    public void closeAll(ResultSet resultSet, Statement statement) throws SQLException {
        if (resultSet != null) {
            resultSet.close();
        }
        if (statement != null) {
            statement.close();
        }
    }

}