为什么我的 PreparedStatement SQL 查询不起作用？仅适用于硬编码字符串答案

【问题标题】：Why doesn't my PreparedStatement SQL query work? Only works with a hardcoded string为什么我的 PreparedStatement SQL 查询不起作用？仅适用于硬编码字符串
【发布时间】：2021-10-21 17:13:54
【问题描述】：

我正在尝试使用PreparedStatement 来生成 SQL 查询。当我使用硬编码 String 或连接时，它工作得非常好，但我完全不知道为什么使用 PreparedStatement 时它不起作用。

public Customer createCustomer(Customer customer) {

     //Ommitted code

     int result = statement.executeUpdate(createPreparedStatementQuery(customer), Statement.RETURN_GENERATED_KEYS)
);

使用 PreparedStatement 创建查询

public static String createPreparedStatementQuery(Customer customer){
    String query = "INSERT INTO customers(Customer_Name, Address, Postal_Code, Phone, Created_By, Last_Updated_By, Division_ID) " +
            "VALUES (?, ?, ?, ?, ?, ?, (SELECT Division_ID FROM first_level_divisions WHERE division = ?));";
    try {
        PreparedStatement statement = ConnectionManager.getConnection().prepareStatement(query);
        statement.setString(1, customer.getName());
        statement.setString(2, customer.getAddress());
        statement.setString(3, customer.getPostalCode());
        statement.setString(4, customer.getPhoneNumber());
        statement.setString(5, customer.getCreatedBy());
        statement.setString(6, customer.getLastUpdatedBy());
        statement.setString(7, customer.getDivision());
        
        System.out.println(statement); //Successfully returns the query
        
        return statement.toString();
    }catch (SQLException e){
        System.out.println(e.getMessage());
        return null;
    }
}

这给出了错误：

您的 SQL 语法有错误；检查手册对应于您的 MySQL 服务器版本，以便使用正确的语法 'com.mysql.cj.jdbc.ClientPreparedStatement 附近：插入客户（客户名称，'在第 1 行

但是，使用通过连接或硬编码创建的字符串，查询执行得非常好。

public static String createConcatQuery(Customer customer) {
    String query =  "INSERT INTO customers(Customer_Name, Address, Postal_Code, Phone, Created_By, Last_Updated_By, Division_ID) " +
            "VALUES ('"
            + customer.getName() + "', '"
            + customer.getAddress() + "', '"
            + customer.getPostalCode() + "', '"
            + customer.getPhoneNumber() + "', '"
            + customer.getCreatedBy() + "', '"
            + customer.getLastUpdatedBy() + "', "
            + "(SELECT Division_ID FROM first_level_divisions WHERE division = '"
            + customer.getDivision() + "'));";
    System.out.println(query);
    return query;
}

String hardCodedQuery = "INSERT INTO customers(Customer_Name, Address, Postal_Code, Phone, Created_By, Last_Updated_By, 

Division_ID) VALUES ('ee', 'ee', 'ee', 'ee', 'test', 'test', (SELECT Division_ID FROM 

first_level_divisions WHERE division = 'Newfoundland and Labrador'));";

我已经复制并粘贴了从日志输出的两个查询。 concat 查询和preparedstatement 查询都返回相同的字符串：

我完全不知道为什么它在这一点上不起作用。有人可以帮我弄清楚我在使用 PreparedStatement 时做错了什么吗？

完整堆栈跟踪：

java.sql.SQLSyntaxErrorException: 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 'com.mysql.cj.jdbc.ClientPreparedStatement: INSERT INTO customers(Customer_Name, ' at line 1
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120)
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
    at com.mysql.cj.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1337)
    at com.mysql.cj.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2117)
    at com.mysql.cj.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1342)
    at sample.data.CustomerRepository.createCustomer(CustomerRepository.java:144)
    at sample.controller.CustomerController.createCustomer(CustomerController.java:165)
    at sample.controller.CustomerController.confirmAlert(CustomerController.java:153)
    at sample.controller.CustomerController.onBtnSaveClick(CustomerController.java:146)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:432)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:410)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$3(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)

【问题讨论】：

executeUpdate 不能在 PreparedStatement 或 CallableStatement 上调用。 docs.oracle.com/javase/7/docs/api/java/sql/Statement.html

标签： java mysql jdbc mysql-connector

【解决方案1】：

您必须在您的createPreparedStatementQuery() 函数中调用statement.executeQuery()。或者您可以从 createPreparedStatementQuery() 函数返回您的语句对象并在您的 createCustomer() 中调用 statement.executeQuery()。

注意您可以根据需要使用statement.executeUpdate() 或statement.executeQuery()。

你的createPreparedStatementQuery() 基本上在做的是它返回原始查询？将其标记到createCustomer() 中的语句对象。外面的语句对象不知道你在里面的语句对象中设置的参数。

【讨论】：

我的错误是认为我必须将PreparedStatement 转换为字符串然后执行statement.executeUpdate(preparedStatementString, Statement.RETURN_GENERATED_KEYS); 当我本可以调用preparedStatement.executeUpdate();