java（JDBC连接数据库）[对PreparedStatement进行封装]

package com.iflytec.ex01;  
  
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;  
  
public class ConnectionDB {  
  
    /** 
     * 数据库驱动类名称 
     */  
    private static final String DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";  
  
    /** 
     * 连接字符串 
     */  
    private static final String URLSTR = "jdbc:sqlserver://localhost:1433; databaseName=Northwind";  
  
    /** 
     * 用户名 
     */  
    private static final String USERNAME = "sa";  
  
    /** 
     * 密码 
     */  
    private static final String USERPASSWORD = "111111";  
  
    /** 
     * 创建数据库连接类 
     */  
    private Connection connnection = null;  
  
    private PreparedStatement preparedStatement = null;  
  
    /** 
     * 创建结果集对象 
     */  
    private ResultSet resultSet = null;  
  
    static {  
        try {  
            // 加载数据库驱动程序   
            Class.forName(DRIVER);  
        } catch (ClassNotFoundException e) {  
            System.out.println("加载驱动错误");  
            System.out.println(e.getMessage());  
        }  
    }  
  
    /** 
     * 建立数据库连接 
     *  
     * @return 
     */  
    public Connection getConnection() {  
        try {  
            // 获取连接   
            connnection = DriverManager.getConnection(URLSTR, USERNAME,  
                    USERPASSWORD);  
        } catch (SQLException e) {  
            System.out.println(e.getMessage());  
        }  
        return connnection;  
    }  
  
    public int executeUpdate(String sql, Object[] params) {  
        int affectedLine = 0;  
        try {  
            connnection = this.getConnection();  
            preparedStatement = connnection.prepareStatement(sql);  
            for (int i = 0; i < params.length; i++) {  
                preparedStatement.setObject(i + 1, params[i]);  
            }  
  
            affectedLine = preparedStatement.executeUpdate();  
  
        } catch (SQLException e) {  
            System.out.println(e.getMessage());  
        } finally {  
            closeAll();  
        }  
        return affectedLine;  
    }  
      
  
    private ResultSet executeQueryRS(String sql, Object[] params) {  
        try {  
            connnection = this.getConnection();  
            preparedStatement = connnection.prepareStatement(sql);  
            for (int i = 0; i < params.length; i++) {  
                preparedStatement.setObject(i + 1, params[i]);  
            }  
  
            resultSet = preparedStatement.executeQuery();  
  
        } catch (SQLException e) {  
            System.out.println(e.getMessage());  
        }   
          
        return resultSet;  
    }  
      
    /** 
     * 获取结果集，并将结果放在List中 
     * @param sql SQL语句 
     * @return List结果集 
     */  
    public List<Object> excuteQuery(String sql, Object[] params) {   
        ResultSet rs = executeQueryRS(sql,params);  
        ResultSetMetaData rsmd = null;  
        int columnCount = 0;  
        try {  
            rsmd = rs.getMetaData();  
            columnCount = rsmd.getColumnCount();  
        } catch (SQLException e1) {  
            System.out.println(e1.getMessage());  
        }  
          
        List<Object> list = new ArrayList<Object>();  
          
        try {  
            while(rs.next()) {  
                Map<String, Object> map = new HashMap<String, Object>();  
                for(int i = 1; i <= columnCount; i++) {  
                    map.put(rsmd.getColumnLabel(i), rs.getObject(i));                 
                }  
                list.add(map);  
            }  
        } catch (SQLException e) {  
            System.out.println(e.getMessage());  
        } finally {  
            closeAll();  
        }  
          
        return list;  
    }  
  
     /** 
     * 释放所有资源 
     */  
    private void closeAll() {  
        // 释放结果集连接   
        if (resultSet != null) {  
            try {  
                resultSet.close();  
            } catch (SQLException e) {  
                System.out.println(e.getMessage());  
            }  
        }  
  
        // 释放声明连接   
        if (statement != null) {  
            try {  
                statement.close();  
            } catch (SQLException e) {  
                System.out.println(e.getMessage());  
            }  
        }  
  
        // 释放数据库连接   
        if (connnection != null) {  
            try {  
                connnection.close();  
            } catch (SQLException e) {  
                System.out.println(e.getMessage());  
            }  
        }  
    }