JDBC 实现对数据库表的增删查操作（案例）

1、创立数据库表 examstudent，表结构如下：

2、向数据表中添加如下数据：

3、创建Student类定义属性名称

package com.atguigu4.exer;

import javax.sound.midi.MidiDevice.Info;

/*
 * Type: IDCard: ExamCard: StudentName: Location: Grade:
 */
public class Student {
	private int flowID;//流水号
	private int type;//考试类型
	private String IDCard;//身份证号
	private String examCard;//准考证号
	private String name;//学生姓名
	private String location;//所在城市
	private int grade;//成绩
	public Student() {
		super();
	}
	public Student(int flowID, int type, String iDCard, String examCard, String name, String location, int grade) {
		super();
		this.flowID = flowID;
		this.type = type;
		IDCard = iDCard;
		this.examCard = examCard;
		this.name = name;
		this.location = location;
		this.grade = grade;
	}
	public int getFloeID() {
		return flowID;
	}
	public void setFloeID(int flowID) {
		this.flowID = flowID;
	}
	public int getType() {
		return type;
	}
	public void setType(int type) {
		this.type = type;
	}
	public String getIDCard() {
		return IDCard;
	}
	public void setIDCard(String iDCard) {
		IDCard = iDCard;
	}
	public String getExamCard() {
		return examCard;
	}
	public void setExamCard(String examCard) {
		this.examCard = examCard;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLocation() {
		return location;
	}
	public void setLocation(String location) {
		this.location = location;
	}
	public int getGrade() {
		return grade;
	}
	public void setGrade(int grade) {
		this.grade = grade;
	}
	@Override
	public String toString() {
		System.out.println("========查询结果=========");
		return Info();
	}
	private String Info() {

		return "流水号："+flowID+"\n四级/六级："+type+"\n身份证号："+IDCard+"\n准考证号："+examCard+
				"\n学生姓名："+name+"\n区域："+location+"\n成绩："+grade;
	}
	 

}

4、创建测试类实现需求

package com.atguigu4.exer;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.Scanner;

import org.junit.Test;

import com.atguigu3.util.JDBCUtils;

/*
 * 练习二：向数据表中增删查数据
 */
public class Exer2Test {
	
	//问题一：向examstudent表中添加一条记录
	/*
	 * Type: IDCard: ExamCard: StudentName: Location: Grade:
	 * 
	 */
	@Test
	public void testInsert() {
		Scanner scanner= new Scanner(System.in);
		System.out.print("四级/六级：");
		int type = scanner.nextInt();
		
		System.out.print("身份证号：");
		String IDCard=scanner.next();
		
		System.out.print("准考证号：");
		String ExamCard=scanner.next();
		
		System.out.print("学生姓名：");
		String StudentName=scanner.next();
		
		System.out.print("所在城市：");
		String Location=scanner.next();
		
		System.out.print("学生成绩：");
		int Grade=scanner.nextInt();
		
		String sql="insert into examstudent(type,IDCard,ExamCard,StudentName,Location,Grade)values(?,?,?,?,?,?)";
		int insertCount = update(sql, type,IDCard,ExamCard,StudentName,Location,Grade);
		if (insertCount>0) {
			System.out.println("添加成功");
		}else {
			System.out.println("添加失败");
		}
		
	}
	//通用的增删改操作（前提是在同一个数据库中）
			public int update(String sql,Object ...args)  {//sql中占位符的个数与可变形参的长度相同
				
				Connection conn=null;
				PreparedStatement ps=null;
				try {
					//1、获取数据库的连接
					 conn = JDBCUtils.getConnectio();
					//2、预编译sql语句，返回PrepareStatement的实例
					ps = conn.prepareStatement(sql);			
					//3、填充占位符
					for(int i=0;i<args.length;i++) {
						ps.setObject(i+1,args[i]);//小心参数声明错误
					}
					//4、执行
					/*
					 * ps.execute()
					 * 如果执行的是查询操作，有返回结果，则此方法返回true
					 * 如果执行增删改操作，没有返回结果，则此方法返回false
					 * 方式一:
					 */
					 //ps.execute();
					//方式二：
					return ps.executeUpdate();
				} catch (Exception e) {
					e.printStackTrace();
				}finally {
					//5、资源的关闭
					JDBCUtils.closeResource(conn, ps);
				}
					return 0;	
			}
			
			
			
			//问题二：根据身份证号或者准考证号查询学生信息
			@Test
			public void queryWithIDCardOrExamCard() {
				System.out.println("请选择您要输入的类型：");
				System.out.println("a.准考证号");
				System.out.println("b.身份证号");
				Scanner scanner=new Scanner(System.in);
				String selection = scanner.next();
				if ("a".equalsIgnoreCase(selection)) {//if (selection.equalsIgnoreCase("a")) {
					System.out.println("请输入准考证号：");				
					String examCard = scanner.next();
					String sql="select FlowID flowID,Type type,IDCard ,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard=?";
					
					Student student = getInstance(Student.class, sql, examCard);
					if (student!=null) {
						System.out.println(student);
					}else {
						System.out.println("输入准考证号有误！");
					}
					
					
				}else if("b".equalsIgnoreCase(selection)) {
					System.out.println("请输入身份证号：");				
					String IDCard = scanner.next();
					String sql="select FlowID flowID,Type type,IDCard ,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where IDCard=?";
					
					Student student = getInstance(Student.class, sql, IDCard);
					if (student!=null) {
						System.out.println(student);
					}else {
						System.out.println("输入身份证号有误！");
					}			
					
				}else {
					System.out.println("您的输入有误，请重新进入程序！");
				}
				
			}
			public <T> T getInstance(Class<T> clazz, String sql,Object...args){
				Connection conn=null;
				PreparedStatement ps=null;
				ResultSet rs=null;
				try {
					conn = JDBCUtils.getConnectio();
					
					ps = conn.prepareStatement(sql);
					for (int i = 0; i < args.length; i++) {
						ps.setObject(i+1,args[i]);
					}
					
					rs = ps.executeQuery();
					//获取结果集的元数据 
					ResultSetMetaData rsmd = rs.getMetaData();
					//通过ResultSetMetaData获取结果集中的列数
					int columnCount = rsmd.getColumnCount();
					
					if(rs.next()) {
						T t=clazz.newInstance();
						//处理结果集一行数据中的每一个列:给T对象指定的属性赋值
						for (int i = 0; i < columnCount; i++) {
							//获取列值
							Object columValue = rs.getObject(i+1);
							
							//获取每个列的列名
							String columnLable = rsmd.getColumnLabel(i+1);
							
							//给t对象指定的columnName属性，赋值为columValue,通过反射
							Field field=clazz.getDeclaredField(columnLable);
							field.setAccessible(true);
							field.set(t, columValue);
						
					}
					return t;
					}
				} catch (Exception e) {
					e.printStackTrace();
				}finally {
					JDBCUtils.closeResource(conn, ps,rs);

				}
				return null;
			}
			
			//问题三：删除指定的学生信息
			@Test
			public void testDeleteByExamCard() {
				System.out.println("请输入学生的考号：");
				Scanner scanner=new Scanner(System.in);
				String examCard=scanner.next();
				//查询指定准考证号的学生
				String sql="select FlowID flowID,Type type,IDCard ,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard=?";
				Student student = getInstance(Student.class, sql, examCard);
				if (student==null) {
					System.out.println("查无此人，请重新输入：");
				}else {
					String sql1="delete from examstudent where examCard=?";
					int deleteCount = update(sql1, examCard);
					if (deleteCount>0) {
						System.out.println("删除成功！");
					}
				}
				
				
			}
			
			//优化以后的操作
			@Test
			public void testDeleteByExamCard1() {
				System.out.println("请输入学生的考号：");
				Scanner scanner=new Scanner(System.in);
				String examCard=scanner.next();
				String sql="delete from examstudent where examCard=?";
				int deleteCount = update(sql, examCard);
				if (deleteCount>0) {
					System.out.println("删除成功！");
				}else {
					System.out.println("查无此人，请重新输入！");
				}
			}
}

5、结果实现
输入身份证号或准考证号可以查询到学生的基本信息：

完成学生信息的删除功能：