我在控制台中收到SQL错误，我试图在没有问号的情况下进行查询，并且工作正常。然而，众所周知，这是非常糟糕的做法，让我接受注射。
以下面的方法为例。它们对我来说都是正确的，它们都在我将问号放入查询之前都在工作，而我所做的所有阅读似乎都反映出我正在正确地进行查询。
public void insert(User user) {
id = user.getId();
name = user.getName();
text = user.getText();
email = user.getEmail();
String query = "INSERT INTO offers (name, email, text) VALUES (?, ?, ?)";
System.out.println(user.getName()+" "+user.getEmail()+" "+user.getText());
try {
System.out.println(query);
ps = conn.prepareStatement(query);
ps.setString(1, name);
ps.setString(2, email);
ps.setString(3, text);
ps.executeUpdate(query);
} catch (SQLException e) {
System.out.println("There was an error in insert: " + e);
e.printStackTrace();
}
}
public void delete(User user) {
name = user.getName();
email = user.getEmail();
String query = "DELETE FROM offers WHERE name= ? AND email=?";
System.out.println(query);
try {
ps = conn.prepareStatement(query);
ps.setString(1, name);
ps.setString(2, email);
ps.executeUpdate(query);
} catch (SQLException e) {
System.out.println("Error while trying to delete "+e);
e.printStackTrace();
}
}
public void update(User user) {
id = user.getId();
name = user.getName();
text = user.getText();
email = user.getEmail();
String query = "UPDATE offers SET name=? , text=? WHERE email= ?";
try {
ps = conn.prepareStatement(query);
ps.setString(1, user.getName());
ps.setString(2, user.getEmail());
ps.setString(3,user.getText());
ps.executeUpdate(query);
} catch (Exception e) {
System.out.println("There was an error in update: " + e);
}
}
public List<User> returnDatabase() {
//will have this method return a list soon
List<User> users = new LinkedList<User>();
User user = null;
String query = "SELECT * FROM offers";
try {
stmt = conn.prepareStatement(query);
rs = stmt.executeQuery(query);
while(rs.next()){
id = rs.getInt("id");
name = rs.getString("name");
email = rs.getString("email");
text = rs.getString("text");
user.setId(id);
user.setName(name);
user.setEmail(email);
user.setText(text);
users.add(user);
System.out.println(id+" "+name+" "+email+" "+text);
}
} catch (Exception e) {
System.out.println("could not return database "+e);
}
return users;
}
public String getSucessful() {
return sucessful;
}
}
控制台
Connected
Fire constructor
Fired
asdf asdf asdf
INSERT INTO offers (name, email, text) VALUES (?, ?, ?)
There was an error in insert: 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 '?, ?, ?)' at line 1
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 '?, ?, ?)' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:377)
at com.mysql.jdbc.Util.getInstance(Util.java:360)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:978)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3887)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3823)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2526)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1618)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1549)
at com.practice.database.MySQLdatabase.insert(MySQLdatabase.java:44)
at com.practice.controller.DatabaseController$Actions.actionPerformed(DatabaseController.java:89)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6525)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3322)
at java.awt.Component.processEvent(Component.java:6290)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4881)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:751)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:702)
at java.awt.EventQueue$3.run(EventQueue.java:696)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:724)
at java.awt.EventQueue$4.run(EventQueue.java:722)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:721)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
答案 0 :(得分：2)
替换
ps.executeUpdate(query);
通过
ps.executeUpdate();
准备语句时已经传递了查询。在执行它时再次传递它是无用的（并导致查询执行与未准备的语句一样）。