无法使用jdbc preparestatement查询mysql数据库

Question

我正在尝试运行下面的jdbc代码来获取对象密钥：

String sqlSelectObjKey = "select OBJ_KEY from obj where OBJ_NM=? and OBJ_TYP_CD='CONN';";


    PreparedStatement statement = null;
    ResultSet rs = null;
    try {           
        statement = connection.prepareStatement(stmtSelectObjKey);
        statement.setString(1, "Postal Connector");

        rs = statement.executeQuery(stmtSelectObjKey);
        while(rs.next()) {
            this.executionLog.setObjKey(rs.getInt("OBJ_KEY"));
        }

    } catch (SQLException e1) {
        e1.printStackTrace();

    } finally {
        if (rs != null) try { rs.close(); } catch (SQLException ignore) {}
        if (statement != null) try { statement.close(); } catch (SQLException ignore) {}
    }

但是每次导致以下异常：

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 '? and OBJ_TYP_CD='CONN'' 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: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.ConnectionImpl.execSQL(ConnectionImpl.java:2484)
    at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1446)
    at appMetadata.ConnectorMetadataLoad.insertExecutionLog(ConnectorMetadataLoad.java:67)
    at appCore.PostalCodeInterface.getPostalData(PostalCodeInterface.java:37)
    at appMain.PostalDataConnector.getPostalData(PostalDataConnector.java:19)
    at PostalDemo.main(PostalDemo.java:14)

直接删除占位符并设置该值即可。

我不确定语法在哪里错误，如果有人可以指出该错误，我将不胜感激。

Answer 1

我收到了您的错误，为什么还要将查询再次分配给preparestatment。

您的代码：

statement = connection.prepareStatement(stmtSelectObjKey);
statement.setString(1, "Postal Connector");
rs = statement.executeQuery(stmtSelectObjKey);

代码应为：

statement = connection.prepareStatement(stmtSelectObjKey);
statement.setString(1, "Postal Connector");
rs = statement.executeQuery();

这就是为什么您收到语法错误的原因。 希望这对您有帮助

Answer 2

删除; 在您的SQL字符串，然后再试一次。

的; 大多数数据库工具中都使用sql字符串来分隔sql字符串，但这不是标准的sql。

Answer 3

代替

statement.executeQuery(stmtSelectObjKey);

采用

statement.executeQuery();

它将工作！

Answer 4

当您使用prepareStatement ，执行语法类似于以下prepareStatement.executeQuery()因此，请如下更改代码

String sqlSelectObjKey = "select OBJ_KEY from obj where OBJ_NM=? and OBJ_TYP_CD='CONN';";


    PreparedStatement statement = null;
    ResultSet rs = null;
    try {           
        statement = connection.prepareStatement(stmtSelectObjKey);
        statement.setString(1, "Postal Connector");

        rs = statement.executeQuery();//Change is here
        while(rs.next()) {
            this.executionLog.setObjKey(rs.getInt("OBJ_KEY"));
        }

    } catch (SQLException e1) {
        e1.printStackTrace();

    } finally {
        if (rs != null) try { rs.close(); } catch (SQLException ignore) {}
        if (statement != null) try { statement.close(); } catch (SQLException ignore) {}
    }

欲了解更多信息， 请点击这里

Answer 5

替换以下查询

String sqlSelectObjKey = "select OBJ_KEY from obj where OBJ_NM=? and OBJ_TYP_CD='CONN';";

与

String sqlSelectObjKey = "select OBJ_KEY from obj where OBJ_NM=? and OBJ_TYP_CD='CONN'";