How Java handles properties resource files

In the Java language, a text file with a .properties extension is used as a resource file. The content format of this type of file is similar to:

#Comment statement
some_key=some_value

form. Lines starting with # are used as comment lines and will be ignored when processed by the ResourceBundle class; the remaining lines can be described in the form of key name=value.

Java's ResourceBundle class can handle files in this form.

The use of the ResourceBundle class is also very simple. Let's use an example to illustrate.

We assume that we have the following 2 properties files:

TestProperties.properties   view plainprint?  #key=value     userIdLabel=User Id:      userNameLabel=User Name:     #key=value userIdLabel=User Id:   userNameLabel=User Name:   TestProperties_zh_CN.properties   view plainprint?  #key=value     userIdLabel=用户ID:      userNameLabel=用户名：     #key=value userIdLabel=用户ID:   userNameLabel=用户名：

You may notice that there is a _zh_CN name in the TestProperties_zh_CN.properties file name, which is actually used for localization of resource files. . What is localization? Let us briefly explain: When we develop the system, we often need to prepare different interfaces for users in different regions. For example, if a system is targeted at both English-speaking users and Chinese users, we must prepare 2 sets of interfaces for the system. The interface (including messages), one set is English interface and the other is Chinese interface. Of course, apart from the different interfaces, the system processes are exactly the same. Of course, it is impossible for us to develop two different systems for them respectively. What should we do? This requires localization of resources. In other words, different resource files are prepared according to the region or language of the user, so that different interfaces can be prepared for different users but the same set of system logic is used.

The two files above are two different sets of resources.

We use the ResourceBundle class to process the code of different resources:

TestProperties.java   view plainprint?  package com.test.properties;          import java.util.Enumeration;     import java.util.Locale;     import java.util.ResourceBundle;          public class TestProperties  {              public static void main(String []args) {     String resourceFile = "com.test.properties.TestProperties";     //创建一个默认的ResourceBundle对象     //ResourceBundle会查找包com.test.properties下的TestProperties.properties的文件     //com.test.properties是资源的包名，它跟普通java类的命名规则完全一样：     //- 区分大小写     //- 扩展名 .properties 省略。就像对于类可以省略掉 .class扩展名一样     //- 资源文件必须位于指定包的路径之下（位于所指定的classpath中）     //另外，对于非西欧字符（比如中日韩文等），需要使用native2ascii命令或类似工具将其转换成ascii码文件格式，否则会显示乱码。     System.out.println("---Default Locale---");     ResourceBundle resource = ResourceBundle.getBundle(resourceFile);          testResourceBundle(resource);          System.out.println("---Locale.SIMPLIFIED_CHINESE---");          //创建一个指定Locale（本地化）的ResourceBundle对象，这里指定为Locale.SIMPLIFIED_CHINESE     //所以ResourceBundle会查找com.test.properties.TestProperties_zh_CN.properties的文件     //     //中文相关的Locale有：     //Locale.SIMPLIFIED_CHINESE : zh_CN     resource = ResourceBundle.getBundle(resourceFile, Locale.SIMPLIFIED_CHINESE);     //Locale.CHINA  : zh_CN     //Locale.CHINESE: zh     testResourceBundle(resource);          //显示     //         }                  private static void testResourceBundle(ResourceBundle resource) {     //取得指定关键字的value值     String userIdLabel = resource.getString("userIdLabel");     System.out.println(userIdLabel);          //取得所有key值     Enumeration enu = resource.getKeys();          System.out.println("keys:");     while(enu.hasMoreElements()) {         System.out.println(enu.nextElement());     }         }     }     package com.test.properties;   import java.util.Enumeration;  import java.util.Locale;  import java.util.ResourceBundle;   public class TestProperties  {       public static void main(String []args) {  String resourceFile = "com.test.properties.TestProperties";  //创建一个默认的ResourceBundle对象  //ResourceBundle会查找包com.test.properties下的TestProperties.properties的文件  //com.test.properties是资源的包名，它跟普通java类的命名规则完全一样：  //- 区分大小写  //- 扩展名 .properties 省略。就像对于类可以省略掉 .class扩展名一样  //- 资源文件必须位于指定包的路径之下（位于所指定的classpath中）  //另外，对于非西欧字符（比如中日韩文等），需要使用native2ascii命令或类似工具将其转换成ascii码文件格式，否则会显示乱码。  System.out.println("---Default Locale---");  ResourceBundle resource = ResourceBundle.getBundle(resourceFile);   testResourceBundle(resource);   System.out.println("---Locale.SIMPLIFIED_CHINESE---");   //创建一个指定Locale（本地化）的ResourceBundle对象，这里指定为Locale.SIMPLIFIED_CHINESE  //所以ResourceBundle会查找com.test.properties.TestProperties_zh_CN.properties的文件  //  //中文相关的Locale有：  //Locale.SIMPLIFIED_CHINESE : zh_CN  resource = ResourceBundle.getBundle(resourceFile, Locale.SIMPLIFIED_CHINESE);  //Locale.CHINA  : zh_CN  //Locale.CHINESE: zh  testResourceBundle(resource);   //显示  //      }            private static void testResourceBundle(ResourceBundle resource) {  //取得指定关键字的value值  String userIdLabel = resource.getString("userIdLabel");  System.out.println(userIdLabel);   //取得所有key值  Enumeration enu = resource.getKeys();   System.out.println("keys:");  while(enu.hasMoreElements()) {      System.out.println(enu.nextElement());  }      }  }

Explanation:

1, for ease of understanding, we put the explanation in the Java source code, here No more details.

2. For the Chinese resource file TestProperties_zh_CN.properties, you need to use the native2ascii command to convert it to ascii code. For example:

native2ascii -encoding UTF-8 c:\TestProperties_zh_CN.properties c:\java\com\test\properties\TestProperties_zh_CN.properties

As for the detailed usage of native2ascii, I will not go into details here. .

3. Save the above three files in the c:\java\com\test\properties\ directory. Among them, TestProperties_zh_CN.properties is a file converted by native2ascii.

4, compile and execute, it will be displayed on the screen:

c:\java\javac com.test.properties.TestProperties.java

c:\java\ java com.test.properties.TestProperties
---Default Locale---
User Id:
keys:
userNameLabel
userIdLabel
---Locale.SIMPLIFIED_CHINESE---
User ID:
keys:
userNameLabel
userIdLabel

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