JDBC 使用正确的语句返回 MySQLSyntaxError 异常

Question

我正在用 java 编写一个与 MySQL 数据库通信的应用程序，当我测试它时，我注意到在表中插入新行的代码抛出了 MySQLSyntaxError 异常，因此我尝试使用 MySQL Workbench 执行相同的 INSERT，它起作用了。有问题的代码是这样的：

public static boolean aggiungiElem(String nome, GrafoGenerico g){
    if(connessioneAperta()){
        try{
            String sqlCommandUser="SELECT USER()";
            String sqlCommandInserim="INSERT INTO salvataggi VALUES ( ? , ? , DEFAULT , NULL );";
            PreparedStatement sUser=conn.prepareStatement(sqlCommandUser);
            ResultSet risultatiUtente=sUser.executeQuery();
            String utente = null;
            while(risultatiUtente.next()){
                utente=risultatiUtente.getString(1);
            }
            sUser.close();
            PreparedStatement sInserim=conn.prepareStatement(sqlCommandInserim);
            sInserim.setString(1, utente);
            sInserim.setString(2, nome);
            //sInserim.setObject(3,g);
            System.out.println(sInserim.toString());
            sInserim.executeUpdate(sqlCommandInserim);
            sInserim.close();
            return true;
        }
        catch(SQLException e){
            e.printStackTrace();
            return false;
        }
    }
    else
        return false;
}

编辑：抱歉，堆栈跟踪是：

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 '? , ? , DEFAULT , NULL )' 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:407)
at com.mysql.jdbc.Util.getInstance(Util.java:382)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3603)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3535)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1989)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2150)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2620)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1664)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1583)
at se.diag.control.clientspec.UtilsClientSQL.aggiungiElem(UtilsClientSQL.java:67)
at se.diag.control.clientspec.UtilsClientSQLTest.testAggiungiElem(UtilsClientSQLTest.java:67)
at se.diag.control.clientspec.UtilsClientSQLTest.testCaricaElem(UtilsClientSQLTest.java:99)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45)
at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66)
at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35)
at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

Answer 1

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，了解在 '? 附近使用的正确语法。 , ? , DEFAULT , NULL )' 在第 1 行

这些占位符 ? 根本不应该出现在 MySQL 端。

看这里，

sInserim.executeUpdate(sqlCommandInserim);

您将原始 SQL 字符串传递到 executeUpdate() 中，而不是使用设置的值执行 PreparedStatement。

将其替换为

sInserim.executeUpdate();

executeUpdate(sqlString) 只能在 Statement 上使用。

---

与具体问题无关，您应该关闭finally 块中的PreparedStatement，以防止出现异常时资源泄漏。顺便说一句，这同样适用于 Connection、Statement 和 ResultSet。