如何在Spring中使用@PropertySource加载的属性文件中配置“动态键”

Question

Using Spring 4 @Configuration annotation, this is how I configure a properties file and refer in my application:

src/main/resources/errors.properties

name.empty.error=name is empty
department.empty.error=department is empty

Java code configuration and usage:

@Configuration
@PropertySource("classpath:errors.properties")
public class Sample {
    @Autowired
    private Environment env;

    public void usage() {
        String errorText = env.getProperty("name.empty.error");
    }

I'd like to specify 'key' of my errors.properties in the following manner:

{0}.empty.error={0} is empty

so that the usage() method would call something like

String errorText1 = env.getProperty("{}.empty.error", "name");
String errorText2 = env.getProperty("{}.empty.error", "department");

How to do this? I remember something like this existed in Struts error message handling.

Answer 1

You need to use MessageSource , which is an interface for resolving messages. ResourceBundleMessageSource is MessageSource implementation which can read from properties file.

You'll need to configure it (I have not tried to compile the source)

@Bean
MessageSource messageSource() {
     ResourceBundleMessageSource source=new  ResourceBundleMessageSource();
     source.setBasenames("messages");
     return source;
}

You'll have to wire it and in the code you would call:

String errorText1 = source.getMessage("empty.error", "name", Locale.US);

and in your messages file you would have:

empty.error = {0} is empty

As a bonus, your app will be ready for internalization.

Answer 2

I think you can do something like this,

 String errorText1 = env.getProperty(String.format("%s.empty.error", "name"));
 String errorText2 = env.getProperty(String.format("%s.empty.error", "department"));

Edit:

It makes no sense, if you use this just to get these specific values from the property file.

But if these values are decided during the run-time (give that all these properties are available in the property file).

You can use,

 String errorText1 = env.getProperty(String.format("%s.empty.error", dynamic-property-value-goes-here));

Answer 3

We can use MessageSource interface for resolving messages.

ResourceBundleMessageSource is MessageSource implementation which can read from properties file.

https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/support/ResourceBundleMessageSource.html

and then call the getMessage() method.

String org.springframework.context.MessageSource.getMessage(String code, Object[] args, String defaultMessage, Locale locale)

---

messages.properties file in classpath [src/main/resources/]

empty.error = {0} is empty

Spring-config file

<bean id="messageSource1" class="org.springframework.context.support.ResourceBundleMessageSource">
  <property name="basenames">
    <value>messages</value>
  </property>
</bean>

Usage in Java class:

@Autowired
private MessageSource messageSource1;

public MessageSource getMessageSource1() {
  return messageSource1;
}

public void setMessageSource1(MessageSource messageSource1) {
  this.messageSource1 = messageSource1;
}

// exact usage in your Java class method

String [] params = new String[]{"value1"};
log.info(this.messageSource1.getMessage("empty.error", params ,"", Locale.US));