2020年11月22日Java学习日记

DaoTest.java

package 人口普查系统;

import static org.junit.Assert.*;

import java.sql.SQLException;

import org.junit.Test;

public class DaoTest {

    @Test
    public void test() throws SQLException {
        Dao dao=new Dao();
        System.out.print(dao.searchByName("2").size());
    }
}

DBUtil.java

package 人口普查系统;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;


public class DBUtil {
    private static String url = "jdbc:mysql://localhost:3306/course?useUnicode=true&characterEncoding=utf8";
    private static String user = "root";
    private static String password = "123";
    private static String jdbcName="com.mysql.jdbc.Driver";
    private Connection con=null;
    public static  Connection getConnection() {
        Connection con=null;
        try {
            Class.forName(jdbcName);
            con=DriverManager.getConnection(url, user, password);
            //System.out.println("数据库连接成功");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            //System.out.println("数据库连接失败");
            e.printStackTrace();
        }
        try {
            con = DriverManager.getConnection(url,user,password);
            System.out.println("连接成功");


        } catch (SQLException e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return con;
    }
    public static void main(String[] args)throws SQLException { 
        Connection conn = getConnection();
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        String sql ="select * from person";
        pstmt = conn.prepareStatement(sql);
        rs = pstmt.executeQuery();
        System.out.println(getConnection());
        while(rs.next()){
            System.out.println("成功");
        }

        }

       // return con;
        
    
    public static void close(Connection con) {
        if(con!=null)
            try {
                con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        
    }
    public static void close(Statement state, Connection conn) {
        if(state!=null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    public static void close(ResultSet rs, Statement state, Connection conn) {
        if(rs!=null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(state!=null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}