If the file does not exist (as determined by the file open error), write the "null" state to the file.

如果该文件不存在(由文件打开错误确定)，则把“null”状态写入文件。

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In Listing 1, you'll find a short program that tries to open a file that is unlikely to exist and reports the error to whomever is running the program, using two different techniques.

在清单1中，您将看到一个简短程序，该程序尝试打开一个不太可能存在的文件，并使用两种不同的方法向运行该程序的用户报告错误。

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Double-click the error to open persistence.xml file.

双击错误以打开persistence . xml文件。

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