Shulou(Shulou.com)06/03 Report--

There are several ways for java to read and write files. In view of this problem, this article introduces the corresponding analysis and solutions in detail, hoping to help more partners who want to solve this problem to find a more simple and easy way.

Two ways for java to read files: java.io and java.lang.ClassLoader

/ / java.io:

File file = new File ("...")

FileInputStream fis = new FileInputStream ("...")

FileReader fr = new FileReader ("...")

/ / ClassLoader:

ClassLoader loader = XXXClass.class.getClassLoader ()

ClassLoader loader2 = Thread.currentThread () .getContextClassLoader ()

URL url = loader.getResource ("...")

File file = new File (url.getFile ())

InputStream input = loader.getResourceAsStream ("...")

Classes in the java.io package always analyze relative pathnames based on the current user directory, that is, whether the relative path works or not depends on the value of user.dir. The system property user.dir is set when JVM starts, and is usually the call directory of the Java virtual machine, that is, the directory where the java command is executed.

For the tomcat/jboss container, user.dir is the% home/bin%/ directory, because this is where we started the web container

When running the program in eclipse, eclipse sets the value of user.dir to the root directory of the project

User directories can be viewed using System.getProperty ("user.dir")

So, it's not a good idea to use java.io to read files, either relative or absolute, and don't use it if you can't use it (in JavaEE).

Use ClassLoader

There are two ways of Class.getResource (), absolute path and relative path. The absolute path starts with /, and the search starts under the root directory of the classpath or jar package

The relative path is relative to the directory where the current class is located, allowing you to use.. Or. To locate the file.

ClassLoader.getResource () can only use an absolute path and does not have to start with /.

These two ways to read resource files are not dependent on user.dir or specific deployment environment, and are recommended (JavaEE).

How to select

Java.io:

Relative to the current user directory path reading; focus on dealing with disk files or pure java project use.

Although the ClassLoader method is more general, it is unreasonable to navigate to the classpath path to read the file if it is not a javaEE environment.

Java.lang.ClassLoader:

Relative path reading relative to classpath; it is recommended to use this method in all javaEE environments.

Usually, ClassLoader can not read too large files, it is suitable for reading web project configuration files, if you need to read large files, or to use the IO package, you can first get the absolute path to the file through ClassLoader, and then pass it to File or other objects, it would be better to read with the objects in the io package.

The answers to the questions about how java can read and write documents are shared here. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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