How to search by an object in springboot

Question

In springboot you can have a repository that extends JpaRepository<User, String>

Now if you want to write a query to that repository, you can write multiple findBy queries such as:

User findByUsername(String username);
User findByFirstName(String firstName);
User findByFirstNameAndLastName(String firstName, String lastName);

then you need matching controllers like:

@RequestMapping(value = "/users/{username}" , method = RequestMethod.GET)
public @ResponseBody List<User> getUser(@PathVariable("username") String username) {
    return userService.findByUsername(username);
}

etc, etc...

I don't want to have to write every single findBy for each combination of elements and create all the matching controllers like that.

So what I want to know is how you can search by a whole object. For example posting something like

{
"username":"freddy"
}

will search by username and equally

{
"firstName":"Fred",
"lastName":"Doe"
}

will search by first and last name.

Is there a way to write both a JpaRepository method and a controller that can take a (in this case) User object with any combination of fields, and perform a search for that?

Thanks.

Indra Basak · Accepted Answer · 2017-11-20 03:59:07Z

2

You can try JPA's Query by Example. JpaRepository extends another interface named QueryByExampleExecutor, which has a quite a few methods for searching by example. Here is a simple example,

// here the first name, last name, and username may be null 
// or not null. Make sure that they are not all at the same time
String firstName = "James";
String lastName = null;
String userName = "jbond";

Example<User> example = Example.of(new User(firstName, lastName, username));
Iterable<User> = repository.findAll(example);

You can do other fancy stuff. Here is an example.

Q. Is there a way to return unique result fields? So in that example, passing firstName would return a unique list of all the lastNames and all the possible userNames

For this type of situations, I haved used native queries. Here is an example,

@Query(value = "SELECT DISTINCT u.lastName FROM User u WHERE u.firstName = ?1", 
       nativeQuery = true)
List<String> findDistinctLastName(String firstName);

edited Nov 20, 2017 at 3:59

answered Nov 19, 2017 at 2:20

Indra Basak

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1 Comment

Wayneio Over a year ago

Is there a way to return unique result fields? So in that example, passing firstName would return a unique list of all the lastNames and all the possible userNames

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