How take always first parameter when requested array type param in spring mvc using #RequestParam - arrays

Question

I wrote this code.
#GetMapping("/test")
public Response search(#RequestParam String value) {
System.out.println(value);
return new Response(value)
}
Some body request like
/test?value=a&value=b&value=c
value binded a,b,c
I want always bind first parmeter. Take a, ignore b, c.
Is there way using #RequestParam?
Or have to use HttpServletRequest and parsing parameter?

Answer 1

In this case you can use #RequestParam List<String> value instead of #RequestParam String value, and get the first value value.get(0) ignore the rest of them
For Example
http://rentacar.com/api/v1/search?make=audi&model=A8&type=6&type=11&type=12&color=RED&color=GREY
Method
public List<Vehicle> search(
#RequestParam(value="make", required=false) String make,
#RequestParam(value="model", required=false) String model,
#RequestParam(value="type", required=false) List<String> types,
#RequestParam(value="color", required=false) List<String> colors)
{
....
}

Answer 2

Great question!
I wrote this code to find out how this works. I included it in the test packages.
#RunWith(SpringRunner.class)
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
#ActiveProfiles("test")
public class ControllerTest {
#LocalServerPort
private int port;
private URL url;
#Autowired
private TestRestTemplate template;
#Before
public void setUp() throws Exception {
this.url = new URL("http://localhost:" + port + "/test?value=a&value=b&value=c");
}
#Test
public void getHello() throws Exception {
ResponseEntity<String> response = template.getForEntity(url.toString(),
String.class);
Assert.assertEquals(HttpStatus.OK, response.getStatusCode());
Assert.assertEquals(response.getBody(), "a");
System.out.println("response = " + response);
}
}
I then modified your code to accept an array of strings, and only pass the first element to your Response Constructor.
Notice the changes in your code in the signature and return statement.
#GetMapping("/test")
public String search(#RequestParam String[] value) {
System.out.println(value);
return new Response(value[0]);
}
With your test, you can now explore using a List type for your request param and quickly see how the behaviour has changed.