JDBC&CRUD练习

博主今日闲来无事,把前一周学的jdbc和数据的增删改查(CRUD)练习了一遍.

代码分为dbinfo.properties(数据库的连接配置), Student.java(javaBean 用于封装对象), DBUtil.java(工具类), TestCRUD.java(测试类)四部分,下面我将一一将以罗列.

先上dbinfo.properties~

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql:///test
name=root
password=mulin123456

其中driverClass值为数据库的连接驱动,url值为需要连接的库路径,jdbc:mysql:///test == jdbc:mysql://localhost:3306/test "///"为本地连接的缩写

接下来就上Student.java代码~

package login.dao;

import java.util.Date;

public class Student {

	private int id;
	private String name;
	private String sex;
	private Date birthday;
	
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "id=" + id + ", name=" + name + ", sex=" + sex + ", birthday=" + birthday;
	}
}

Student.java简单易懂,我就不多做介绍了.

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下来就上工具类DBUtil.java~

package database.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;

public class DBUtil {

	private static String driverClass;
	private static String url;
	private static String name;
	private static String password;
	
	static {
		//此对象用于加载properties文件数据
		ResourceBundle rb = ResourceBundle.getBundle("dbinfo");
		driverClass = rb.getString("driverClass");
		url = rb.getString("url");
		name = rb.getString("name");
		password = rb.getString("password");
		
		try {
			Class.forName(driverClass);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	/*得到连接的方法*/
	public static Connection getConnection() throws Exception {
		return DriverManager.getConnection(url, name, password);
	}
	
	/*关闭资源的方法*/
	public static void closeAll(ResultSet rs, Connection conn, Statement stmt) {
		if (rs != null) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			rs = null;    // 方便gc回收
		}
			
		if (stmt != null) {
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			stmt = null;
		}

		if (conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			conn = null;
		}
	}
}

DBUtil.java里主要封装的是jdbc,将数据库的连接以及关闭方法封装起来,以便测试类的调用.

下来就轮到压轴代码出场了~

先附上数据库初始内容:

1.查

package jdbcTest;

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

import org.junit.Test;

import database.util.DBUtil;
import login.dao.Student;

public class TestCRUD {
	
	@Test	
	public void testSelect() {     // 数据查找
		
		Connection conn = null;
		PreparedStatement stmt = null;
		ResultSet rs = null;
		
		try {
			conn = DBUtil.getConnection();
			String sql = "SELECT * FROM student";
			stmt = conn.prepareStatement(sql);    // 预编译
			//执行sql语句,并返回结果 
			rs = stmt.executeQuery();
			List<Student> list = new ArrayList<> ();
			
			/* 加载驱动 
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection("jdbc:mysql:///test", "root", "mulin123456");    // /// 表本地连接
			stmt = conn.createStatement();*/
			
			while (rs.next()) {
				Student student = new Student();
				student.setId(rs.getInt(1));    // "id"
				student.setName(rs.getString("name"));
				student.setSex(rs.getString("sex"));
				student.setBirthday(rs.getDate(4));
				
				list.add(student);
				
			}
			
			for (Student l : list) {
				System.out.println(l);
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally {   
			
			DBUtil.closeAll(rs, conn, stmt);
		}
	}

这一段是数据的查找,我进行的只是简单的SELECT * FROM student输出所有数据的操作,大家尽可以用复杂些的sql语句练练手哦~

数据查找显示:

2.增

@Test	
	public void testInsert() {     // 数据增添
		
		Connection conn = null;
		PreparedStatement stmt = null;
		
		try {
			conn = DBUtil.getConnection();
			stmt = conn.prepareStatement("INSERT INTO student VALUES(?,?,?,?)");   // 预编译
			stmt.setInt(1, 5);     // 1表示第一个问号“？”
			stmt.setString(2, "striner");
			stmt.setString(3, "女");
			stmt.setString(4, "1997-02-18");
			
			int i = stmt.executeUpdate();
			
			if (i > 0) {
				System.out.println("INSERT SUCCESS!");
			} 
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBUtil.closeAll(null, conn, stmt);
		}
	}

增添数据测试:

数据库中内容显示:

3.改

	@Test	
	public void testUpdate() {     // 数据修改
		
		Connection conn = null;
		PreparedStatement stmt = null;
		
		try {
			conn = DBUtil.getConnection();
			stmt = conn.prepareStatement("UPDATE student SET name=?,sex=?,birthday=? WHERE id=?");   // 预编译
			stmt.setString(1, "xyz");
			stmt.setString(2, "女");
			stmt.setString(3, "2017-1-8");
			stmt.setInt(4, 1);
			
			int i = stmt.executeUpdate();
			
			if (i > 0) {       // i > 0 表执行成功
				System.out.println("UPDATE SUCCESS!");
			} 
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBUtil.closeAll(null, conn, stmt);
		}
	}

数据修改结果:

数据库内容显示:

4.删

	@Test	
	public void testDelect() {     // 数据删除
		
		Connection conn = null;
		PreparedStatement stmt = null;
		
		try {
			conn = DBUtil.getConnection();
			stmt = conn.prepareStatement("DELETE FROM student WHERE id=?");   // 预编译
			stmt.setInt(1, 5);
			int i = stmt.executeUpdate();
			
			if (i > 0) {       // i > 0 表执行成功
				System.out.println("DELETE SUCCESS!");
			} 
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBUtil.closeAll(null, conn, stmt);
		}
	}
}

数据删除测试:

此时数据库内容显示如下:

emmmm,这篇博客就到这就画上句点了.喜欢就请关注我哦,你们的关注是我最大的动力~

想了解git代码请移步:https://github.com/striner/javaCode/blob/master/JDBC%26CRUD%E7%BB%83%E4%B9%A0

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