#spring-data-rest

Aprende la forma más simple de escribir un API REST con Java utilizando Spring Data REST !

En posts anteriores se explicó como hacer una API rest utilizando Spring Data, Spring REST y Spring Boot, en este post se explicará una forma aún más simple de hacerlo haciendo uso de Spring Data REST.

1. Configuración

El primer paso será crear un proyecto Maven que tenga como padre el siguiente proyecto:

org.springframework.boot spring-boot-starter-parent 1.5.9.RELEASE

While doing some proof of concept using Spring Data Rest i realized about one tricky thing related securization of endpoints in Spring Data Rest. 

Spring Data Rest has done a great job, and securization is easily implemented using usual @Secured, @PreAuthorize, @PostAuthorize, @PreFilter, and @PostFilter. Using these annotations aside with expression language linked with Spring ACL allows to access a very powerful securization mechanism (look for more in documentation). 

As usual, these annotations can be used at class level and method level, and is in this second scenario where you must be careful. It is very important for you to understand the hierarchy of your repository since there are plenty overloaded methods and, some times, you can end with unexpected situations if you are not aware of this.

I have been using Spring Data Rest and trying out the Neo4J implementation. This was going well but as it was on Build Snapshots, and now on Milestone 1, things change.

The first thing to note, as it currently stands, it is not as easy as it should be to create query methods in the repository. For example:

Member findByName(@Param("name") String name);

This will not work as expected, the error returned is:

org.neo4j.cypher.ParameterNotFoundException: Expected a parameter named 0

So after much searching on forums, looking through documentation and example code, there was nothing that would help with this issue. So late one night, I had a brainwave to try something. I created a custom Cypher query to return the data I needed.

@Query("start member=node:Member(name={name}) return member") Member findByName(@Param("name") String name);

Above you can see that in the @Query, I have a parameter to be injected called name, and the param on the request is also called name. After this update, alas!, everything worked as expected.

After all of this I thought all of my troubles were behind me, but Spring Data changed something in the core and nothing worked any more, there was an error for a MissingIndexException. It was saying that "Member" was not Indexed.

Again, more forum searching, more documentation reading, more trawling through example code and trying to guess what the correct code would be, there were no answers for this issue again!

While reading through the documentation I was reading about the different types of Repositories that were available to Spring Data Neo4J and seen that IndexRepository and NamedIndexRepository were available. So I replaced GraphRepository with both of these, doing this caused the repositories to disappear. I then had an idea to to extend more than one repository:

public interface MemberRepository extends GraphRepository, NamedIndexRepository

The entity class now looks like:

@NodeEntity public class Member { @GraphId private Long id; @Indexed("name-search") private String name; //Getters and Setters }

And now everything is hunky dory again. The search works as expected.

I know what it's like coming up against all of these issues when using a new technology, so thanks to a friend who persuaded me to write this blog, I hope this is useful to someone, somewhere, someday.