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java – com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException：为’PRIMARY’重复输入”

Java开发
2023-11-04

我从今天起就得到了这个例外.昨天事情很好.我会发布我的代码：public void enterStaff() throws ClassNotFoundException, SQLException {try {Class.forName(com.mysql.jdbc.Driver);connect = DriverManager.getC...

我从今天起就得到了这个例外.昨天事情很好.我会发布我的代码：

public void enterStaff() throws ClassNotFoundException, SQLException {
    try {
        Class.forName("com.mysql.jdbc.Driver");
        connect = DriverManager
                .getConnection("jdbc:mysql://localhost:3306/project?"
                        + "user=root&password=virus");
        statement = connect.createStatement();

        preparedStatement = connect
                .prepareStatement("SELECT count(*)FROM information_schema.tables\n"
                        + "WHERE table_schema = 'project' AND table_name = 'staff'");
        rs = preparedStatement.executeQuery();
        rs.next();
        int chk = rs.getInt(1);

        if (chk != 1) {
            preparedStatement = connect
                    .prepareStatement("create table staff (staffname varchar(30) primary key);");
            preparedStatement.executeUpdate();
        }

        preparedStatement = connect
                .prepareStatement("insert into staff values(?);");
        preparedStatement.setString(1, addSubName.getText());

        preparedStatement.executeUpdate();
    } catch (ClassNotFoundException | SQLException e) {
        throw e;
    } finally {
        close2();
    }

}

private void close2() {
    try {

        if (statement != null) {
            statement.close();
        }

        if (connect != null) {
            connect.close();
        }
    } catch (SQLException e) {

    }
}

我正在尝试创建一个只有一列的表,该列是主键.当代码第一次运行时,表格就会被创建.但价值没有进入.当时没有例外.但是当我第二次尝试输入值时,会出现异常.

我怎么能纠正这个？如果有人需要查看更多代码,我会发布它.

这是用户输入数据的代码：

    addSubName = new TextField();
    addSubName.setPromptText("Staff Name");
    addSubName.setPrefSize(200, 30);

    final Button b2 = new Button("Add");
    b2.setFont(Font.font("Calibri", FontWeight.BOLD, 17));
    b2.setPrefSize(70, 30);
    b2.setStyle(" -fx-base: #0066ff;");
    b2.setTextFill(Color.BLACK);
    b2.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent e) {

            data.add(new Staff(addSubName.getText()));
            addSubName.clear();

            try {
                enterStaff();
            } catch (ClassNotFoundException ex) {
                Logger.getLogger(AddStaff.class.getName()).log(Level.SEVERE, null, ex);
            } catch (SQLException ex) {
                Logger.getLogger(AddStaff.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    });

例外细节是：

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '' for key 'PRIMARY'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1040)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4120)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4052)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2503)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2664)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2794)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
at addstaff.AddStaff.enterStaff(AddStaff.java:149)
at addstaff.AddStaff$2.handle(AddStaff.java:100)
at addstaff.AddStaff$2.handle(AddStaff.java:92)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Node.fireEvent(Node.java:6867)
at javafx.scene.control.Button.fire(Button.java:179)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193)
at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336)
at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3311)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3151)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3106)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2248)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
at com.sun.glass.ui.View.handleMouseEvent(View.java:530)
at com.sun.glass.ui.View.notifyMouse(View.java:924)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:17)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:67)
at java.lang.Thread.run(Thread.java:744)

解决方法:

你应该删除;在你的SQL查询中：

错误查询：

prepareStatement("create table staff (staffname varchar(30) primary key);");

preparedStatement = connect.prepareStatement("insert into staff values(?);");

正确的查询是：

prepareStatement("create table staff (staffname varchar(30) primary key)");

preparedStatement = connect.prepareStatement("insert into staff values(?)");

检查你的插入查询

而且,我认为你的INSERT值在db中,那个查询太错了,只提到了tablename,你不应该提到columnname.所以你应该在你的查询中添加tablename.

错误查询：

insert into staff values(?)

正确查询：

    INSERT INTO table_name
    VALUES (value1,value2,value3,...);

参考此链接：

http://www.w3schools.com/sql/sql_insert.asp

更新：1

错误的代码：

statement = connect.createStatement();
preparedStatement = connect
                .prepareStatement("SELECT count(*)FROM information_schema.tables\n"
                        + "WHERE table_schema = 'project' AND table_name = 'staff'");
        rs = preparedStatement.executeQuery();
        rs.next();

你应该改变：样品

Class.forName(driverName).newInstance();
con=DriverManager.getConnection(connectionUrl+dbName,user,password);
st = con.createStatement();
String sql="SELECT * FROM employees";
rs=st.executeQuery(sql);

注意：

>你不应该调用sql查询.
>而且,你正在使用preparedStatement来调用,你应该使用chage to statement
> preparedStatement无法解决.

喜欢,

string sql=....sql query...;
statement.executeQuery(sql)

更新：2： – &GT样品

public class User 
{
private String empname;
public String getEmpName()
{
    return empname;
}
public void setEmpName(String empname)
{
    this.empname=empname;
}

public void addUser(User user)
{
    try
    {
        PreparedStatement ps;
        ps=connection.prepareStatement("INSERT INTO employee (empname,empaddress,depname) VALUES (?,?,?)");
        ps.setString(1, user.getEmpName());
        ps.setString(2, user.getEmpAddress());
        ps.setString(3, user.getDepName());
        ps.executeUpdate();
    }
    catch(Exception e)
    {
        System.out.println(e);
    }
}

本文标题为：java – com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException：为’PRIMARY’重复输入”

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