The Java connection to the mysql database uses the mysql-JDBC jar package, and the executeQuery() method is used for the query operation.
Code:
Student class
package test;
public class Student {
private int id;
private String name;
private int age;
public Student(int id, String name, int age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
}
}
Sql class:
package test;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Sql {
Connection con;
public Connection getConn() throws SQLException, ClassNotFoundException {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8", "root", "helloworld");
System.out.println(con);
return con;
}
public int addStu(Student st) throws SQLException, ClassNotFoundException {
con=getConn();
try {
con = getConn();
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace ();
}
String sql_insert = "insert into student(id, name, age) values(?, ?, ?)";
PreparedStatement pst = con.prepareStatement(sql_insert);
pst.setInt(1, st.getId());
pst.setString(2, st.getName());
pst.setInt(3, st.getAge());
int rest = pst.executeUpdate();
pst.close();
con.close();
return rest;
}
public int deleteStu(int id) throws ClassNotFoundException, SQLException {
con=getConn();
String sql="delete from student where id=?";
PreparedStatement pst = con.prepareStatement(sql);
pst = con.prepareStatement(sql);
pst.setInt(1,id);
int result=pst.executeUpdate();
pst.close();
con.close();
return result;
}
public int updateStu(int id, int flag) throws SQLException, ClassNotFoundException {
con=getConn();
Scanner cin = new Scanner(System.in);
String name;
int age;
String sql;
int rst = 0;
if(flag == 1) {
name = cin.next();
sql = "update student set name = ? where id = ?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, name);
pst.setInt(2, id);
rst = pst.executeUpdate();
pst.close();
}
else if(flag == 2) {
age = cin.nextInt();
sql = "update student set age = ? where id = ?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setInt(1, age);
pst.setInt(2, id);
rst = pst.executeUpdate();
pst.close();
}
else if(flag == 3) {
age = cin.nextInt();
name = cin.next();
sql = "update student set name = ?, age = ? where id = ?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, name);
pst.setInt(2, age);
pst.setInt(3, id);
rst = pst.executeUpdate();
pst.close();
}
con.close();
return rst;
}
public List<Student> queryAll() throws SQLException, ClassNotFoundException {
con=getConn();
List<Student> stu = new ArrayList<Student>();
String sql = "select * from student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rst = pst.executeQuery();
while (rst.next()) {
int id = rst.getInt(1);
String name = rst.getString(2);
int age = rst.getInt(3);
stu.add(new Student(id, name, age));
//System.out.println(id + "---" + name + "---" + age);
}
pst.close();
con.close();
return stu;
}
public void queryById(int id) throws SQLException, ClassNotFoundException {
con=getConn();
String sql = "select name, age from student where id=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setInt(1, id);
ResultSet rst = pst.executeQuery();
if(rst.next()!= false) {
String name = rst.getString("name");
int age = rst.getInt("age");
System.out.println("Student number "+id+": "+"\n"+"Name: "+name+"\n"+"Age: "+age+"\n");
}
pst.close();
con.close();
}
}
Main class;
package test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Main {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Scanner cin = new Scanner(System.in);
Sql mysql_obj = new Sql();
int order = 0;
System.out.println("Please enter the command to operate: ");
System.out.println("Enter 1 to add student information");
System.out.println("Enter 2 to delete student information");
System.out.println("Enter 3 to modify student information");
System.out.println("Enter 4 to query according to student ID");
System.out.println("Enter 5 to query all student information");
while(cin.hasNext()) {
order = cin.nextInt();
if(order == 1) {
System.out.println("Enter student information id name age");
Student stu = new Student(cin.nextInt(), cin.next(), cin.nextInt());
int rst = mysql_obj.addStu(stu);
if(rst == 1) {
System.out.println("success!");
}
else {
System.out.println("failed!");
}
}
else if(order == 2) {
System.out.println("Enter student id");
int id = cin.nextInt ();
int rst = mysql_obj.deleteStu(id);
if(rst == 1) {
System.out.println("success!");
}
else {
System.out.println("failed!");
}
}
else if(order == 3) {
System.out.println("Enter student id");
int id = cin.nextInt ();
System.out.println("Change Name Input 1 Change Age Input 2 Change both Input 3");
int flag = cin.nextInt();
int rst = mysql_obj.updateStu(id, flag);
if(rst == 1) {
System.out.println("success!");
}
else {
System.out.println("failed!");
}
}
else if(order == 4) {
System.out.println("Enter student id");
int id = cin.nextInt ();
mysql_obj.queryById(id);
}
else if(order == 5) {
List<Student> stu = new ArrayList<Student>();
stu = mysql_obj.queryAll();
for(Student st: stu) {
System.out.println(st.toString());
}
}
}
}
}