管理 Java 中的异常

发布于 2024-11-17 22:50:19 字数 656 浏览 3 评论 0原文

我正在做一个小型数据库程序。

Connection connection = DriverManager.getConnection(..., ..., ...);

String createTable= "CREATE TABLE Employee ...";

try
{
    Statement stmt = connection.createStatement ();
    stmt.executeUpdate(createTable);
    stmt.close();
    connection.close ();
}
catch(Exception Ex)
{
    System.out.println("Erreur : " + Ex.toString());
}

当您运行该程序时，一切都会好起来，但第二次您会收到此异常：

重复的表名称：Employee

好的，我知道如何管理异常，但是如何管理每个可能的异常。就像：

IF 异常是重复错误THEN 显示自定义重复消息。

IF 这是一个重复的主键THEN 显示另一条错误消息，依此类推。

谢谢。

原文

I'm doing a small database program.

Connection connection = DriverManager.getConnection(..., ..., ...);

String createTable= "CREATE TABLE Employee ...";

try
{
    Statement stmt = connection.createStatement ();
    stmt.executeUpdate(createTable);
    stmt.close();
    connection.close ();
}
catch(Exception Ex)
{
    System.out.println("Erreur : " + Ex.toString());
}

When you run the program everything is going to be fine, but the second time you will get this Exception :

Duplicate table name : Employee

Ok fine I know how to manage Exceptions, but how about managing every possible Exception. Like :

IF the Exception is a Duplicattion error THEN display a custom Duplicate message.

IF it's a duplicate primary key THEN display another error message and so on.

Thanks.

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弥繁 2024-11-24 22:50:19

如果要处理特定异常，则需要多个 catch 语句。

try {
    // some code that may throw an exception
}
catch (DuplicateKeyException e) {
    // handle a duplicate key exception
}
catch (DuplicateTableException e) {
    // handle a duplicate table exception - note this probably isn't the correct exception, you'll need to look up what is actually thrown
}
catch (Exception e) {
    // handle all other exceptions in a non-specific way
}

You need multiple catch statements if you want to handle specific exceptions.

try {
    // some code that may throw an exception
}
catch (DuplicateKeyException e) {
    // handle a duplicate key exception
}
catch (DuplicateTableException e) {
    // handle a duplicate table exception - note this probably isn't the correct exception, you'll need to look up what is actually thrown
}
catch (Exception e) {
    // handle all other exceptions in a non-specific way
}

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ゃ懵逼小萝莉 2024-11-24 22:50:19

您必须解析异常方法字符串才能获取实际 SQL 异常的“子类型”：

 try {
   // ...
 } catch (SQLException e) {
  if (e.getMessage().toLowerString().contains("duplicate table name")) {
   // handle duplicate table name problem
  } else if ( /* ... */ ) {
   // ...
  }
 }

You'll have to parse the exceptions method string to get the "subtype" of the actual SQL exception:

 try {
   // ...
 } catch (SQLException e) {
  if (e.getMessage().toLowerString().contains("duplicate table name")) {
   // handle duplicate table name problem
  } else if ( /* ... */ ) {
   // ...
  }
 }

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