【Java编程】建立一个简单的JDBC连接-Drivers, Connection, Statement and PreparedStatement

package com.andieguo.jdbc;

import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
 * 该类封装了连接和关闭数据库连接操作
 * 
 * @author andieguo
 * 
 */
public class DBConnection {

	public static Connection getConnection() {
		Properties props = new Properties();
		FileInputStream fis = null;
		Connection con = null;
		try {
			fis = new FileInputStream("db.properties");
			props.load(fis);
			// 加载驱动
			Class.forName(props.getProperty("DB_DRIVER_CLASS"));
			// 创建一个连接
			con = DriverManager.getConnection(props.getProperty("DB_URL"), props.getProperty("DB_USERNAME"), props.getProperty("DB_PASSWORD"));
		} catch (IOException | SQLException | ClassNotFoundException e) {
			e.printStackTrace();
		}
		return con;
	}

	// 关闭ResultSet
	public static void closeResultSet(ResultSet rs) {
		if (rs != null) {
			try {
				rs.close();
				rs = null;
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	// 关闭Statement
	public static void closeStatement(Statement stm) {
		if (stm != null) {
			try {
				stm.close();
				stm = null;
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	// 关闭PreparedStatement
	public static void closePreparedStatement(PreparedStatement pstm) {
		if (pstm != null) {
			try {
				pstm.close();
				pstm = null;
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	// 关闭Connection
	public static void closeConnection(Connection con) {
		if (con != null) {
			try {
				con.close();
				con = null;
			} catch (SQLException e) {
				e.printStackTrace();
			}
			con = null;
		}
	}

}

package com.andieguo.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class DBHelper {

	public static void queryAllByStatement() {
		List<User> users = new ArrayList<User>();
		Connection conn = DBConnection.getConnection();
		Statement stmt = null;
		ResultSet rs = null;
		try {
			stmt = conn.createStatement();
			rs = stmt.executeQuery("select * from user");
			while (rs.next()) {
				User user = new User();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setGender(rs.getBoolean("gender"));
				user.setRegtime(rs.getDate("regtime"));
				System.out.println(user.toString());
				users.add(user);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBConnection.closeResultSet(rs);
			DBConnection.closeStatement(stmt);
			DBConnection.closeConnection(conn);
		}
	}

	public static void queryById(Integer id) {
		Connection conn = DBConnection.getConnection();
		Statement stmt = null;
		ResultSet rs = null;
		try {
			stmt = conn.createStatement();
			rs = stmt.executeQuery("select * from user where id = " + id);
			while (rs.next()) {
				User user = new User();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setGender(rs.getBoolean("gender"));
				user.setRegtime(rs.getDate("regtime"));
				System.out.println(user.toString());
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBConnection.closeResultSet(rs);
			DBConnection.closeStatement(stmt);
			DBConnection.closeConnection(conn);
		}
	}


}

package com.andieguo.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBHelper {

	public static void queryAllByprepareStatement() {
		List<User> users = new ArrayList<User>();
		Connection conn = DBConnection.getConnection();
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			ps = conn.prepareStatement("select * from user");
			rs = ps.executeQuery();
			while (rs.next()) {
				User user = new User();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setGender(rs.getBoolean("gender"));
				user.setRegtime(rs.getDate("regtime"));
				System.out.println(user.toString());
				users.add(user);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBConnection.closeResultSet(rs);
			DBConnection.closeStatement(ps);
			DBConnection.closeConnection(conn);
		}
	}

	public static void queryPrepareById(Integer id) {
		Connection conn = DBConnection.getConnection();
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			ps = conn.prepareStatement("select * from user where id = ?");
			ps.setInt(1, id);// 设置占位符参数
			rs = ps.executeQuery();
			while (rs.next()) {
				User user = new User();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setGender(rs.getBoolean("gender"));
				user.setRegtime(rs.getDate("regtime"));
				System.out.println(user.toString());
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBConnection.closeResultSet(rs);
			DBConnection.closeStatement(ps);
			DBConnection.closeConnection(conn);
		}
	}

}

package com.andieguo.jdbc;

import junit.framework.TestCase;

public class DBHelperTest extends TestCase {

	public void getConnectionTest(){
		System.out.println(DBConnection.getConnection());
	}
	
	public void queryAllByStatementTest(){
		DBHelper.queryAllByStatement();
	}
	
	public void queryAllByprepareStatementTest(){
		DBHelper.queryAllByprepareStatement();
	}
	
	public void queryByIdTest(){
		DBHelper.queryById(2);
	}
	
	public void queryByPrepareIdTest(){
		DBHelper.queryPrepareById(3);
	}
	
}