练习

练习题1：从控制台向数据库的表customers中插入一条数据，表结构如下：

`Exer1Test.java

package com.atguigu4.exer;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.util.Scanner;

import org.junit.Test;

import com.atguigu3.util.JDBCUtils;
//课后练习1
public class Exer1Test {
	
	@Test
	public void testInsert(){
		Scanner scanner = new Scanner(System.in);
		System.out.print("请输入用户名：");
		String name = scanner.next();
		System.out.print("请输入邮箱：");
		String email = scanner.next();
		System.out.print("请输入生日：");
		String birthday = scanner.next();//'1992-09-08'
		
		String sql = "insert into customers(name,email,birth)values(?,?,?)";
		int insertCount = update(sql,name,email,birthday);
		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
	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.getConnection();
			// 2.预编译sql语句，返回PreparedStatement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;
			 * 如果执行的是增、删、改操作，没有返回结果，则此方法返回false.
			 */
			//方式一：
//			return 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;
	}

}

练习题2：创立数据库表 examstudent，表结构如下：

向数据表中添加如下数据：

代码实现1：插入一个新的student 信息
请输入考生的详细信息
Type: IDCard: ExamCard: StudentName: Location: Grade:信息录入成功!

代码实现2：在 eclipse中建立 java 程序：输入身份证号或准考证号可以查询到学生的基本信息。结果如下：

代码实现3：完成学生信息的删除功能

Student.java

package com.atguigu4.exer;

/*
 * 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 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;
	}
	public int getFlowID() {
		return flowID;
	}
	@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;
	}
	
	
}

Exer2Test.java

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 javax.swing.plaf.synth.SynthStyle;

import org.junit.Test;

import com.atguigu3.util.JDBCUtils;

//课后练习2
public class Exer2Test {

	// 问题1：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("考试成绩：");
		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
	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.getConnection();
			// 2.预编译sql语句，返回PreparedStatement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;
			 * 如果执行的是增、删、改操作，没有返回结果，则此方法返回false.
			 */
			// 方式一：
			// return 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2：根据身份证号或者准考证号查询学生成绩信息
	@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("输入的准考证号有误！");
			}
			
		}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("输入的身份证号有误！");
			}
		}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.getConnection();

			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
			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
				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 columnName = rsmd.getColumnName(i + 1);
					String columnLabel = 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(columnLabel);
					field.setAccessible(true);
					field.set(t, columValue);
				}
				return t;
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.closeResource(conn, ps, rs);

		}

		return null;
	}
	
	//问题3：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");
		}
		
	}
}