How can I make properties in properties files mandatory in Spring?

Question

I have an ApplicationContext.xml file with the following node:

<context:property-placeholder 
location="classpath:hibernate.properties, classpath:pathConfiguration.properties" />

It specifies that both properties files will be used by my application.

Inside pathConfiguration.properties, some paths are defined, such as:

PATH_ERROR=/xxx/yyy/error
PATH_SUCCESS=/xxx/yyy/success

A PathConfiguration bean has setters for each path.

The problem is: when some of those mandatory paths are not defined, no error is thrown. How and where should I handle this problem?

Answer 1

I'm not sure if I fully understand your issue, but there are probably a variety of ways to approach this. One would be to make the paths mandatory by using constructor injection. In the constructor you could then validate the incoming values and if null for example, throw BeanInitializationException instances.

Answer 2

The standard behaviour of the PropertyPlaceholder that is configured via <context:property-placeholder ... /> throws an exception when a property cannot be resolved once it is required in some place as long as you do not configure it otherwise.

For your case if you have a Bean that requires some properties like this, it will fail when the value cannot be resolved. For example like this:

public class PropertiesAwareBean {

  @Value("${PATH_ERROR}")
  private String errorPath;

  String getErrorPath() {
    return errorPath;
  }

}

If you want to relax the PropertyPlaceholder and don't make it throw an Exception when a property cannot be resolved you can configure the PropertyPlaceholder to ignore unresolvable properties like this <context:property-placeholder ignore-unresolvable="true" ... />.

Answer 3

One way to reinforce the verification of parameters is to switch to a classical PropertyPlaceholderConfigurer bean in your beans file.

The PropertyPlaceholderConfigurer has properties which you can use to tweak its behavior and specify either an exception is thrown or not if some key is missing (take a look at setIgnoreUnresolvablePlaceholders or setIgnoreResourceNotFound).

If I remember correctly, in Spring 2.5, only the location attribute is supported for <context:property-placeholder> (things might have changed though).