我要使用用户输入的driverID，如果用户输入了id，则将onJob更改为true。
因此，例如，如果用户输入1作为驱动程序ID，则ID为1的驱动程序会将onJob变量更改为1。
这是我目前的代码；
public class TaxiDriver {
//String driverLocation = DRIVERFIRSTLOCATION;
//String destinationintoAPI;
//JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/DRIVER";
//Database credentials
static final String USER = "user";
static final String PASS = "password";
String driverId;
static Scanner reader = new Scanner(System.in);
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Connected database successfully...");
System.out.println("Assign a driver to a jo...");
reader.nextInt();
//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql = "UPDATE Drivers " +
"SET OnJob = 1 WHERE id = (driverId)";
stmt.executeUpdate(sql);
// Now you can extract all the records
// to see the updated records
sql = "SELECT id, license, first, last, OnJob, Email, Telephone, Address, Postcode, Veichle FROM Drivers";
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) {
//retrieve by column name
int id = rs.getInt("id");
int license = rs.getInt("license");
String first = rs.getString("first");
String last = rs.getString("last");
int OnJob = rs.getInt("OnJob");
String Email = rs.getString("Email");
String Telephone = rs.getString("Telephone");
String Address = rs.getString("Address");
String Postcode = rs.getString("Postcode");
String Veichle = rs.getString("Veichle");
//Display
System.out.print("ID: " + id);
System.out.print(", license: " + license);
System.out.print(", First: " + first);
System.out.print(", Last: " + last);
System.out.print(", Email; " + Email);
System.out.print(", Telephone; " + Telephone);
System.out.print(", Address; " + Address);
System.out.print(", Postcode; " + Postcode);
System.out.print(", Veichle;" + Veichle);
if (OnJob == 0) {
System.out.println(": Driver is aviliable for pickup");
} else {
System.out.println(": Driver is not aviliable for pickup");
}
}
rs.close();
} catch (SQLException se) {
//Handle errors for JDBC
se.printStackTrace();
} catch (Exception e) {
//Handle errors for Class.forName
e.printStackTrace();
} finally {
//finally block used to close resources
try {
if (stmt != null)
conn.close();
} catch (SQLException se) {
}// do nothing
try {
if (conn != null)
conn.close();
} catch (SQLException se) {
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end JDBCExample
现在，我遇到了这些错误。
Connecting to a selected database...
Tue May 03 00:18:28 BST 2016 WARN: Establishing SSL connection without server's identity verification is not recommended.
According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set.
For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'.
You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Connected database successfully...
Assign a driver to a jo...
2
Creating statement...
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'driverId' in 'where clause'
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:404)
at com.mysql.jdbc.Util.getInstance(Util.java:387)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:939)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2547)
at com.mysql.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1541)
at com.mysql.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2605)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1469)
at TaxiDriver.main(TaxiDriver.java:71)
Goodbye!
提前非常感谢。
最佳答案
首先，您实际上需要在某个地方将值读入driverId。
除此之外，问题出在您的SQL语句上。你有：
String sql = "UPDATE Drivers " +
"SET OnJob = 1 WHERE id = (driverId)";
您要告诉数据库查找记录的
id列的值等于其driverId列的值的记录。您需要在SQL中获取
driverId变量的值，而不是将实际的字符“ driverId”放入SQL中（如您所见），该字符被解释为列的名称。使用您的方法，您需要执行以下操作：
String sql = "UPDATE drivers SET OnJob=1 WHERE id=" + driverId;
但是动态SQL是危险的，最好使用
PreparedStatement。这样可以清理用户输入并防止SQL注入攻击。String sql = "UPDATE drivers SET OnJob=1 WHERE id=?";
PreparedStatement ps = connection.createPreparedStatement(sql);
ps.setInt(1, Integer.parseInt(driverId));
ResultSet rs = ps.executeQuery();