我必须用 Java 创建项目才能上学。它键入我我有错误的语法但是当我将命令从错误消息复制到 MySQL 服务器时，一切正常并且信息被插入到表中。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;
import com.mysql.jdbc.StatementInterceptor;
public class main {
public static void main(String[] args) {
String dbHost="localhost";
String dbDatabase="cars";
String dbUser = "root";
String dbPassword = "";
int Select;
Scanner input = new Scanner(System.in);
Cars cars = new Cars();
CarDAO carDAO = new CarDAO();
System.out.println("Choose option: ");
System.out.println("1. Create a new car");
System.out.println("2. Update entry of the car");
System.out.println("3. Mark the car as sold");
System.out.println("4. View all cars that are for sale ");
System.out.println("5. Search for cars");
Select = input.nextInt();
switch (Select){
case 1: {
carDAO.createCar(cars);
break;
}
case 2:{
carDAO.changeEntry(cars);
break;
}
case 3:{
carDAO.soldCar(cars);
break;
}
case 4:{
carDAO.showCars(cars);
break;
}
case 5:{
carDAO.search(cars);
break;
}
}
try {
// register driver
Class.forName("com.mysql.jdbc.Driver");
// Make Connection Url
String connectionUrl = "jdbc:mysql://" + dbHost
+ "/" + dbDatabase
+ "?user=" + dbUser
+ "&password=" + dbPassword;
//open Connection
Connection conn = DriverManager.getConnection(connectionUrl);
// Code to create sql and run it will go here
// create SQL
String sql = "use cars; " + carDAO.sql;
// prepare Statement
PreparedStatement ps = conn.prepareStatement(sql);
// execute SQL
ps.executeUpdate();
// close connection
conn.close();
}catch (ClassNotFoundException cnfe){
throw new RuntimeException(cnfe);
}catch (SQLException sqle) {
throw new RuntimeException(sqle);
}
}
}
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;
public class CarDAO {
String type;
int price;
String date;
int ID = 0;
String sql;
String year;
String month;
String day;
Scanner input = new Scanner(System.in);
Cars cars = new Cars();
main Main = new main();
public void update (Cars cars){
}
public void delete (Cars cars){
}
public void createCar (Cars cars){
System.out.println("Type: ");
cars.setType(input.nextLine());
System.out.println("Price: ");
cars.setPrice(input.nextInt());
input.nextLine();
System.out.println("Made in year: ");
year = input.nextLine();
System.out.println("month: ");
month = input.nextLine();
System.out.println("day: ");
day = input.nextLine();
date = year + month + day;
cars.setDate(date);
ID = ID + 1;
cars.setId(ID);
sql = "INSERT INTO cars (Type, Price, Date) VALUES (" + "'" + cars.getType() + "'" + ", " + cars.getPrice() + ", " + cars.getDate() + ");";
}
public void changeEntry (Cars cars){
}
public void soldCar (Cars cars){
}
public void showCars (Cars cars){
}
public void search (Cars cars){
}
}
public class Cars {
int id;
String type;
String date;
int price;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public int getPrice() {
return price;
}
public void setPrice(int price) {
this.price = price;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
@Override
public String toString() {
return "Car [id=" + getId() + ", type=" + getType() + ", price=" + getPrice() + " date =" + getDate() + "]";
}
}
错误信息:
Exception in thread "main" java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO cars (Type, Price, Date) VALUES ('nwm', 50, 1991827)' at line 1
at main.main(main.java:80)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO cars (Type, Price, Date) VALUES ('nwm', 50, 1991827)' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1053)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4096)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4028)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2490)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2734)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
at main.main(main.java:73)
最佳答案
String sql = "use cars; " + carDAO.sql;
^^^^^^^^^^^^^^
标准的 MySQL 连接不允许在单个查询中使用多个语句，作为对一种形式的 sql 注入(inject)攻击的基本防御。将事情分成两个查询:
query("use cars;");
query(carDAO.sql);
请注意，use 查询并不是真正必要的。您可以在连接字符串中指定默认数据库。您已经有了 dbDatabase，但没有使用它。
关于Java MySQL——错误的语法，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36020599/