My learning diary

Spring Boot Interceptors

A neat trick to log HTTP requests and responses in a Spring Boot project is through interceptors. To log requests and responses between the client and the server, I use the HandlerInterceptor (Introduction to Spring MVC HandlerInterceptor). To create this interceptor, simply extend the HandlerInterceptor interface. By overriding the various methods available, you can intercept the request and/or response at different points of time. For example, preHandle is executed before the request is executed (i.

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Numerical IDs in MongoDB

Auto-generated IDs in MongoDB are “strange” strings. I quote “strange” because they are actually derived not out of nowhere despite looking like they had nothing to do with anything. But to users, these IDs are strange. I had a collection of documents with a name property. Originally, name was annotated with @Id. But it meant that I could not change the value of name. name was also annotated with regex validation (@Pattern(.

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Abstract classes and AOP

I wanted to avoid writing boilerplate code for CRUD in Spring Boot. But I failed - I could not make my child aspect get along with my child controller. Before adopting AOP, I had an abstract controller which the child controller inherited. CRUD worked well and I no longer needed to repeat the code for simple CRUD anymore. I was happy. // MyAbstractController public abstract class MyAbstractController<T extends UniversalModel> { private final .

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Iterator to Stream

With Google Guava, you can transform an Iterator into a Stream with But that API is only available from Guava 21. If you don’t want to use Guava or if your Guava version is below 21, you need an additional step to convert your Iterator to a Stream: Stream<String> stream = Spliterators.spliteratorUnknownSize( iterator, Spliterator.ORDERED ), false ); Reference: mkyong.

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No qualifying bean

In one of my previous posts, I avoided auto-configuring primitives. Otherwise, the No qualifying bean error will occur. Today, I couldn’t avoid that anymore. I had to auto-configure a boolean so that the consumer can enable or disable a feature in application.yml. So, how did I resolve this issue? I used @Value("{someKey:someDefault}") final boolean someFlag in the caller constructor. Before that, I tried attaching only @Bean to the getter, but it didn’t work out.

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