How to read configuration files automatically through Java annotation
Automatic reading of configuration files through Java annotation can simplify the reading process of configuration files, making the code more concise and maintainable. The following is an example code for implementation:
Firstly, it is necessary to define an annotation class to annotate the information of the configuration file that needs to be read:
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Config {
String value() default "";
}
Next, you can create a tool class to read the configuration file:
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.Properties;
public class ConfigReader {
public static void readConfig(Object obj) {
Class<?> clazz = obj.getClass();
//Obtain annotation information
Config config = clazz.getAnnotation(Config.class);
if (config == null) {
return;
}
String filePath = config.value();
if (filePath.isEmpty()) {
return;
}
//Read Configuration File
try (FileInputStream input = new FileInputStream(filePath)) {
Properties properties = new Properties();
properties.load(input);
//Set attribute values
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
String fieldName = field.getName();
String propertyValue = properties.getProperty(fieldName);
if (propertyValue != null) {
field.set(obj, propertyValue);
}
}
}Catch (IOException | IllegalAccessException e){
e.printStackTrace();
}
}
}
Add annotations on the class that needs to read the configuration file and specify the path to the configuration file:
@Config("config.properties")
public class AppConfig {
private String serverUrl;
private String apiKey;
// getter and setter methods
}
Finally, call the configuration file reading method at the entrance of the application:
public class Main {
public static void main(String[] args) {
AppConfig config = new AppConfig();
ConfigReader.readConfig(config);
System.out.println("Server URL: " + config.getServerUrl());
System.out.println("API Key: " + config.getApiKey());
}
}
Summary:
Automatic reading of configuration files through Java annotation can greatly simplify the reading process of configuration files and improve the maintainability of code. Annotate the path of the configuration file that needs to be read by defining annotations, and then read the content of the configuration file through reflection mechanisms and attribute settings, and set it to the corresponding attributes. This allows for the use of annotations in the code to specify the path of the configuration file, without the need for explicit reading of the configuration file and assignment of properties.
