java 读取属性文件时如何关闭fileInputStream

how to close the fileInputStream while reading the property file

提问by Beginner

I have following code :

我有以下代码：

    // Read properties file.
     Properties properties = new Properties();
     try {
     properties.load(new FileInputStream("filename.properties"));
     } catch (FileNotFoundException e) {
     system.out.println("FileNotFound");
     }catch (IOException e) {
     system.out.println("IOEXCeption");
     }

Is it required to close the FileInputStream? If yes, how do I do that? I am getting a bad practice error in my code checklist . Asking it to put finally block.

是否需要关闭 FileInputStream？如果是，我该怎么做？我的代码清单中出现了错误的做法错误。要求它把 finally 块。

回答by hmjd

You must the close the FileInputStream, as the Propertiesinstance will not. From the Properties.load()javadoc:

您必须关闭FileInputStream，因为Properties实例不会。从Properties.load()javadoc：

The specified stream remains open after this method returns.

此方法返回后，指定的流保持打开状态。

Store the FileInputStreamin a separate variable, declared outside of the tryand add a finallyblock that closes the FileInputStreamif it was opened:

将 the 存储FileInputStream在一个单独的变量中，在 the 之外声明try并添加一个finally块，FileInputStream如果它被打开，则关闭它：

Properties properties = new Properties();
FileInputStream fis = null;
try {
    fis = new FileInputStream("filename.properties");
    properties.load(fis);
} catch (FileNotFoundException e) {
    system.out.println("FileNotFound");
} catch (IOException e) {
    system.out.println("IOEXCeption");
} finally {
    if (null != fis)
    {
        try
        {
            fis.close();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

---

---

Use try-with-resourcessince Java 7:

从 Java 7 开始使用try-with-resources：

final Properties properties = new Properties();
try (final FileInputStream fis =
         new FileInputStream("filename.properties"))
{
    properties.load(fis);
} catch (FileNotFoundException e) {
    system.out.println("FileNotFound");
} catch (IOException e) {
    system.out.println("IOEXCeption");
}

回答by Keppil

You should always close your streams, and doing it in the finallyblock is a good practice. The reason for this is that the finallyblock always gets executed, and you want to make sure that the stream is always closed, even if Something Bad happens.

你应该总是关闭你的流，在finally块中这样做是一个很好的做法。这样做的原因是该finally块总是被执行，并且您希望确保流始终关闭，即使发生了一些不好的事情。

    FileInputStream inStream = null;
    try {
        inStream = new FileInputStream("filename.properties");
        properties.load(inStream);
    } catch (FileNotFoundException e) {
        System.out.println("FileNotFound");
    } catch (IOException e) {
        System.out.println("IOEXCeption");
    } finally {
        try {
            inStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

If you are using Java 7, this becomes much easier, since a new try-withsyntax was introduced. Then you can write like this:

如果您使用的是 Java 7，这将变得更加容易，因为try-with引入了新的语法。然后你可以这样写：

try(FileInputStream inStream = new FileInputStream("filename.properties")){
       properties.load(inStream);
   } catch (FileNotFoundException e) {
        System.out.println("FileNotFound");
   } catch (IOException e) {
        System.out.println("IOEXCeption");
}

and the stream is closed automatically.

并且流会自动关闭。

回答by M. Abbas

here is an example:

这是一个例子：

    public class PropertiesHelper {
    public static Properties loadFromFile(String file) throws IOException {
        Properties properties = new Properties();
        FileInputStream stream = new FileInputStream(file);
        try {
            properties.load(stream);
        } finally {
            stream.close();
        }
        return properties;
    }
}

回答by Sylvain

You can use Lombok @Cleanup to do it simply. http://projectlombok.org/features/Cleanup.html

您可以使用 Lombok @Cleanup 来简单地做到这一点。 http://projectlombok.org/features/Cleanup.html

 Properties properties = new Properties();
 try {
   @Cleanup FileInputStream myFis = new FileInputStream("filename.properties");
   properties.load(myFis);
 } catch (FileNotFoundException e) {
   System.out.println("FileNotFound");
 }catch (IOException e) {
   System.out.println("IOEXCeption");
 }

Or, only if your are using Java 7, there is the "try with resource" new feature. http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

或者，仅当您使用 Java 7 时，才有“尝试资源”新功能。 http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

 Properties properties = new Properties();
 try (FileInputStream myFis = new FileInputStream("filename.properties")) {
   properties.load(myFis);
 } catch (FileNotFoundException e) {
   System.out.println("FileNotFound");
 }catch (IOException e) {
   System.out.println("IOEXCeption");
 }