【java源碼】對mysql數據庫的封裝（精華版）

數據庫連接是件很麻煩的事，特別是封裝數據庫，讓我們java編程不再有煩惱

代碼如下：

import java.sql.Connection;

public class JDBC {
	private final String drive="com.mysql.jdbc.Driver";
	private final String url="jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8";
	private final String name="root";
	private final String password="123456";
	private Connection con=null;
	
	public JDBC(){//構造方法加載數據庫驅動		
		try {
			Class.forName(drive).newInstance();
		} catch (Exception e) {		
			System.out.println("數據庫加載失敗！");			
		}		
	}	
	public boolean creatConnection(){//創建數據庫連接
		
		try {
			con=DriverManager.getConnection(url,name,password);
			con.setAutoCommit(true);
		} catch (SQLException e) {
			
		}
		return true;
	}
	public boolean executeUpdate(String sql){//對數據表的增加，修改和刪除的操作
		if(con==null){
			creatConnection();		
		}
		try{
			Statement s=con.createStatement();
			int i=s.executeUpdate(sql);
			System.out.println("操作成功，所影響的記錄數爲："+String.valueOf(i));
			return true;
		}catch(Exception e){
			return false;
		}
		
	}	
	
	
	
		
	public ResultSet executeQuery(String sql){//數據庫的查詢操作
		ResultSet rs;
		try{
			if(con==null){
			creatConnection();		
			}
			Statement s=con.createStatement();
			 rs=s.executeQuery(sql);		
		 	return rs;
		}catch(Exception e){
			return null;		
		}	
			
	}


	public void closeConnection(){//關閉數據庫連接
		if(con==null){		
			try {
				con.close();
			}catch (SQLException e) {
			}		
		}
	}	
	

basedao封裝

import java.lang.reflect.Field;
import java.net.URL;
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;

/**
 * 基礎DAO類
 * @author LYF
 */
public class BaseDao {
	
	/**
	 * 連接數據庫的URL
	 */
	private static String url;

	/**
	 * 登錄數據庫用戶名
	 */
	private static String user;

	/**
	 * 登錄數據庫密碼
	 */
	private static String password;

	/**
	 * 所有線程共享的線程容器
	 */
	private static ThreadLocal<Map<String, Object>> threadLocal = null;

	//靜態塊中實例化線程容器並裝載數據庫驅動
	static {
		init();
	}
	
	private static void init(){
		threadLocal = new ThreadLocal<Map<String, Object>>();
		try {
			Properties pro=new Properties();
			pro.load(ClassLoader.getSystemResource("db.properties").openStream());
			user=pro.getProperty("user");
			password=pro.getProperty("password");
			url=pro.getProperty("url");
			Class.forName(pro.getProperty("driver"));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * 獲取連接對象Connection
	 * @return
	 * @throws SQLException
	 */
	public Connection getConnection() throws SQLException {
		//從線程中取出保存數據
		Map<String, Object> threadMap = threadLocal.get();
		if (null == threadMap) {
			threadMap = new HashMap<String, Object>();
			threadLocal.set(threadMap);
		}
		Connection conn = (Connection) threadMap.get("conn");
		if (null == conn || conn.isClosed()) {
			conn = DriverManager.getConnection(url, user, password);
			threadMap.put("conn", conn);
		}
		return conn;
	}

	/**
	 * 泛型方法(執行查詢DQL)
	 * @param <T>
	 * @param cla
	 * @param sql
	 * @param params
	 * @return
	 * @throws SQLException
	 */
	public <T> List<T> executeQuery(Class<T> cla, String sql, Object... params)
			throws SQLException {
		//獲取連接對象
		Connection conn = this.getConnection();
		//創建預編譯語句對象
		PreparedStatement pstat = conn.prepareStatement(sql);
		// 將產生的語句對象放置到線程中
		PreparedStatement oldpstat = (PreparedStatement) threadLocal.get().put("pstat", pstat);
		//如果線程中有舊的語句對象則關閉它
		if (null != oldpstat)oldpstat.close();
		// 設置預編譯佔位符參數(參數從1開始)
		for (int i = 0; i < params.length; i++) {
			pstat.setObject(i + 1, params[i]);
		}
		
		List<T> list = new ArrayList<T>();
		//執行查詢返回結果集
		ResultSet res = pstat.executeQuery();
		//將結果集放置到線程中
		ResultSet oldRes = (ResultSet) threadLocal.get().put("res", res);
		//如果線程中有舊的結果集則關閉它
		if (null != oldRes)oldRes.close();
		
		//獲取結果集元數據
		ResultSetMetaData rsmd=res.getMetaData();
		//返回結果集中字段數量(列的數量)
		int colNum=rsmd.getColumnCount();
		try {
			T t = null;
			while (res.next()) {//遍歷結果集中的所有記錄
				t = cla.newInstance();//每循環一次生成一個實體對象
				for(int i=0;i<colNum;i++){//循環記錄中的每個字段
					//取出字段的名稱
					String fieldName=rsmd.getColumnLabel(i+1);
					//取出字段的值
					Object object=res.getObject(fieldName);
					//獲取實體類的字段
					Field field=cla.getDeclaredField(fieldName);
					//打開private權限的字段訪問權限
					field.setAccessible(true);
					//設置實體類對象字段屬性值
					field.set(t, object);
				}
				list.add(t);//將實體對象添加的返回列表中
			}
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		} catch (SecurityException e) {
			e.printStackTrace();
		}
		return list;
	}
	
	/**
	 * 執行增刪改(DML)
	 * @param sql
	 * @param params
	 * @return
	 */
	public int executeUpdate(String sql,Object... params) throws SQLException{
		Connection conn = this.getConnection();
		PreparedStatement pstat = conn.prepareStatement(sql);
		PreparedStatement oldpstat = (PreparedStatement) threadLocal.get().put("pstat", pstat);
		if (null != oldpstat)oldpstat.close();
		for (int i = 0; i < params.length; i++) {
			pstat.setObject(i + 1, params[i]);
		}
		//執行DML返回影響行數
		return pstat.executeUpdate();
	}
	
	/**
	 * 執行增加(insert)並且返回主鍵
	 * @param sql
	 * @param params
	 * @return
	 */
	public int[] executeInsert(String sql,Object... params) throws SQLException{
		Connection conn = this.getConnection();
		PreparedStatement pstat = conn.prepareStatement(sql,PreparedStatement.RETURN_GENERATED_KEYS);
		PreparedStatement oldpstat = (PreparedStatement) threadLocal.get().put("pstat", pstat);
		if (null != oldpstat)oldpstat.close();
		for (int i = 0; i < params.length; i++) {
			pstat.setObject(i + 1, params[i]);
		}
		//返回影響行數(就是插入的記錄數量)
		int count=pstat.executeUpdate();
		//定義保存數據庫生成的主鍵的數組
		int[] keys=new int[count];
		//獲取主鍵結果集
		ResultSet res=pstat.getGeneratedKeys();
		//將結果集放置到當前線程中
		ResultSet oldRes = (ResultSet) threadLocal.get().put("res", res);
		if(null!=oldRes)oldRes.close();
		//遍歷結果集,將結果集合中的所有主鍵取出來放到數組中
		for(int i=0;res.next();i++){
			keys[i]=res.getInt(1);
		}
		return keys;
	}
	
	/**
	 * 關閉所有的連接(從線程中取出所有JDBC對象並關閉它們)
	 * @throws SQLException
	 */
	public void closeAll() throws SQLException{
		Map<String,Object> map=threadLocal.get();
		Connection conn=(Connection)map.get("conn");
		PreparedStatement pstat=(PreparedStatement)map.get("pstat");
		ResultSet res=(ResultSet)map.get("res");
		if(null!=res)res.close();
		if(null!=pstat)pstat.close();
		if(null!=conn)conn.close();
	}
}

}

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