复习：JDBC工具类并实现增删改查

JDBC工具类

package bull01.JDBCbasis;

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

/**
 * 
 * @author 45度炸
 * JDBC工具类
 */
public class JDBCUtils {
    private static final String driverClass;
    private static final String url;
    private static final String userName;
    private static final String passWord;

    static{
        //获取配置文件内容
        Properties properties = null;
        try {
            InputStream is = new FileInputStream("src/jdbc.properties");
            properties = new Properties();
            properties.load(is);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         driverClass = properties.getProperty("driverClass");
         url = properties.getProperty("url");
         userName = properties.getProperty("userName");
         passWord = properties.getProperty("passWord");
    }


    //注册驱动
    public static void loadDriver() {
        try {
            Class.forName(driverClass);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    //获得连接
    public static Connection getConnection() {
        Connection conn = null;
        try {
            loadDriver();
            conn = DriverManager.getConnection(url, userName, passWord);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
     public static void closeResource(ResultSet rs,PreparedStatement psmt,Connection conn) {
         if(rs != null) {
             try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
             //垃圾回收尽快回收对象
             rs = null;
         }
         if(psmt != null) {
             try {
                psmt.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
             psmt = null;
         }
         if(conn != null) {
             try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
             conn = null;
         }
     }
}

测试类实现增删改查

package bull01.JDBCbasis;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import org.junit.Test;
/**
 * 
 * @author 45度炸
 * JDBC测试类 
 */
public class JDBCTest {
    //查询
    @Test
    public void demo1() {
        //获得连接（工具类里会先注册驱动）
        Connection conn = null;
        //conn连接数据库获得语句执行者psmt
        PreparedStatement psmt = null;
        //psmt执行后获得结果集rs
        ResultSet rs =null;
        try {
            conn = JDBCUtils.getConnection();
            String sql = "select * from category";
            psmt = conn.prepareStatement(sql);
            rs = psmt.executeQuery();

            while(rs.next()) {
                System.out.println(rs.getInt("cid")+"---"+rs.getString("cname"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(rs, psmt, conn);
        }
    }
    //添加
    @Test
    public void demo2() {
        Connection conn = null;
        PreparedStatement psmt = null;
        ResultSet rs =null;

        try {
            //获得连接
            conn = JDBCUtils.getConnection();
            //获得语句执行者
            String sql = "insert into category values (null,?)";
            psmt = conn.prepareStatement(sql);
            //设置参数
            psmt.setString(1, "书包");
            int i = psmt.executeUpdate();
            if(i > 0) {
                System.out.println("添加成功!");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(rs, psmt, conn);
        }
    }

    //修改
    @Test
    public void demo3() {
        Connection conn = null;
        PreparedStatement psmt = null;
        ResultSet rs = null;
        try {
            //获得连接
            conn = JDBCUtils.getConnection();
            //psmt语句执行者
            String sql = "update category set cname = ? where cid = ?";
            psmt = conn.prepareStatement(sql);
            psmt.setString(1, "鞋子");
            psmt.setInt(2, 5);
            int i = psmt.executeUpdate();
            if(i > 0) {
                System.out.println("修改成功!");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(rs, psmt, conn);
        }
    }

    //删除
    @Test
    public void demo4() {
        Connection conn = null;
        PreparedStatement psmt = null;
        ResultSet rs = null;
        try {
            //获得连接
            conn = JDBCUtils.getConnection();
            //psmt语句执行者
            String sql = "delete from category where cid = ?";
            psmt = conn.prepareStatement(sql);
            psmt.setInt(1, 5);
            int i = psmt.executeUpdate();
            if(i > 0) {
                System.out.println("删除成功！");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(rs, psmt, conn);
        }
    }
}