我正试图从教科书中重新创建这个程序。教科书使用jdbc :: odbc桥，所以我将其更改为ucanaccess。它还使用longbinary作为密码类型，并且我无法识别它将其更改为二进制。这是我收到的输出：
删除索引＆amp;桌子......
无法删除UserStocks表上的主键：UCAExc ::: 4.0.2意外令牌：开启
创建表............
使用主键索引创建Stocks表...
使用主键索引创建Users表...
创建UserStocks表...
创建UserStocks表主键索引...
插入用户的异常：UCAExc ::: 4.0.2 net.ucanaccess.triggers.TriggerException：org.hsqldb.types.BinaryData无法强制转换为java.lang.Integer net.ucanaccess.triggers.TriggerException：org .hsqldb.types.BinaryData无法强制转换为java.lang.Integer
创建数据库。
显示数据库中的数据......
用户表包含：
股票表不包含任何记录。
UserStocks表不包含任何记录。
以下是代码：
import java.sql.*;
import java.io.*;
public class MakeDB
{
public static void main(String[] args) throws Exception
{
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
String url = "jdbc:ucanaccess://C:/Users/Sarah/workspace/StockTracker/StockTracker.mdb";
Connection con = DriverManager.getConnection(url);
Statement stmt = con.createStatement();
// The following code deletes each index and table, if they exist.
// If they do not exist, a message is displayed and execution continues.
System.out.println("Dropping indexes & tables ...");
try
{
stmt.executeUpdate("DROP INDEX PK_UserStocks ON UserStocks");
}
catch (Exception e)
{
System.out.println("Could not drop primary key on UserStocks table: "
+ e.getMessage());
}
try
{
stmt.executeUpdate("DROP TABLE UserStocks");
}
catch (Exception e)
{
System.out.println("Could not drop UserStocks table: "
+ e.getMessage());
}
try
{
stmt.executeUpdate("DROP TABLE Users");
}
catch (Exception e)
{
System.out.println("Could not drop Users table: "
+ e.getMessage());
}
try
{
stmt.executeUpdate("DROP TABLE Stocks");
}
catch (Exception e)
{
System.out.println("Could not drop Stocks table: "
+ e.getMessage());
}
///////// Create the database tables /////////////
System.out.println("\nCreating tables ............");
// Create Stocks table with primary key index
try
{
System.out.println("Creating Stocks table with primary key index...");
stmt.executeUpdate("CREATE TABLE Stocks ("
+"symbol TEXT(8) NOT NULL "
+"CONSTRAINT PK_Stocks PRIMARY KEY, "
+"name TEXT(50)"
+")");
}
catch (Exception e)
{
System.out.println("Exception creating Stocks table: "
+ e.getMessage());
}
// Create Users table with primary key index
try
{
System.out.println("Creating Users table with primary key index...");
stmt.executeUpdate("CREATE TABLE Users ("
+"userID TEXT(20) NOT NULL "
+"CONSTRAINT PK_Users PRIMARY KEY, "
+"lastName TEXT(30) NOT NULL, "
+"firstName TEXT(30) NOT NULL, "
+"pswd BINARY(254), "
+"admin BIT"
+")");
}
catch (Exception e)
{
System.out.println("Exception creating Users table: "
+ e.getMessage());
}
// Create UserStocks table with foreign keys to Users and Stocks tables
try
{
System.out.println("Creating UserStocks table ...");
stmt.executeUpdate("CREATE TABLE UserStocks ("
+"userID TEXT(20) "
+"CONSTRAINT FK1_UserStocks REFERENCES Users (userID), "
+"symbol TEXT(8), "
+"CONSTRAINT FK2_UserStocks FOREIGN KEY (symbol) "
+"REFERENCES Stocks (symbol))");
}
catch (Exception e)
{
System.out.println("Exception creating UserStocks table: "
+ e.getMessage());
}
// Create UserStocks table primary key index
try
{
System.out.println("Creating UserStocks table primary key index...");
stmt.executeUpdate("CREATE UNIQUE INDEX PK_UserStocks "
+"ON UserStocks (userID, symbol) "
);
}
catch (Exception e)
{
System.out.println("Exception creating UserStocks index: "
+ e.getMessage());
}
// Create one administrative user with password as initial data
String userID = "admin01";
String firstName = "Default";
String lastName = "Admin";
String initialPswd = "admin01";
Password pswd = new Password(initialPswd);
boolean admin = true;
PreparedStatement pStmt =
con.prepareStatement("INSERT INTO Users VALUES (?,?,?,?,?)");
try
{
pStmt.setString(1, userID);
pStmt.setString(2, lastName);
pStmt.setString(3, firstName);
pStmt.setBytes(4, serializeObj(pswd));
pStmt.setBoolean(5, admin);
pStmt.executeUpdate();
}
catch (Exception e)
{
System.out.println("Exception inserting user: "
+ e.getMessage());
}
pStmt.close();
// Read and display all User data in the database.
ResultSet rs = stmt.executeQuery("SELECT * FROM Users");
System.out.println("Database created.\n");
System.out.println("Displaying data from database...\n");
System.out.println("Users table contains:");
Password pswdFromDB;
byte[] buf = null;
while(rs.next())
{
System.out.println("Logon ID = "
+ rs.getString("userID"));
System.out.println("First name = "
+ rs.getString("firstName"));
System.out.println("Last name = "+rs.getString("lastName"));
System.out.println("Administrative = "+rs.getBoolean("admin"));
System.out.println("Initial password = "+initialPswd);
buf = rs.getBytes("pswd");
if (buf != null)
{
System.out.println("Password Object = "
+ (pswdFromDB=(Password)deserializeObj(buf)));
System.out.println(" AutoExpires = "+ pswdFromDB.getAutoExpires());
System.out.println(" Expiring now = "+ pswdFromDB.isExpiring());
System.out.println(" Remaining uses = "
+ pswdFromDB.getRemainingUses()+"\n");
}
else
System.out.println("Password Object = NULL!");
}
rs = stmt.executeQuery("SELECT * FROM Stocks");
if(!rs.next())
System.out.println("Stocks table contains no records.");
else
System.out.println("Stocks table still contains records!");
rs = stmt.executeQuery("SELECT * FROM UserStocks");
if(!rs.next())
System.out.println("UserStocks table contains no records.");
else
System.out.println("UserStocks table still contains records!");
stmt.close(); // closing Statement also closes ResultSet
} // end of main()
// Method to write object to byte array and then insert into prepared statement
public static byte[] serializeObj(Object obj)
throws IOException
{
ByteArrayOutputStream baOStream = new ByteArrayOutputStream();
ObjectOutputStream objOStream = new ObjectOutputStream(baOStream);
objOStream.writeObject(obj); // object must be Serializable
objOStream.flush();
objOStream.close();
return baOStream.toByteArray(); // returns stream as byte array
}
// Method to read bytes from result set into a byte array and then
// create an input stream and read the data into an object
public static Object deserializeObj(byte[] buf)
throws IOException, ClassNotFoundException
{
Object obj = null;
if (buf != null)
{
ObjectInputStream objIStream =
new ObjectInputStream(new ByteArrayInputStream(buf));
obj = objIStream.readObject(); // throws IOException, ClassNotFoundException
}
return obj;
}
}
非常感谢任何帮助！
答案 0 :(得分：0)
你的程序中有一些错误的逻辑：
第1步。删除索引
第2步。删除表
第3步。创建表格
在第1步中，逻辑表明您的表不存在，因此索引也不会退出，因此您将获得此异常。
不像表格或数据库，您可以检查您的索引是否存在，以避免此问题您不需要删除索引，因为当您删除表格时，也是索引将被掺杂检查这个（Does dropping a table in MySQL also drop the indexes?）。
注意：为避免在创建和删除数据库，表时出现问题，您可以使用IF NOT EXISTS，例如：
DROP TABLE Stocks IF EXISTS
CREATE TABLE Stocks IF NOT EXISTS (...)