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Пример на Kotlin для конвертирования JSON массива в список объектов.

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Пример на Kotlin для конвертирования JSON массива в список объектов. Дан сервис:


@RestController
@RequestMapping("/company")
@Api(tags = ["Rest Company"])
class CompanyCtrl(val companyService: CompanyService) {
    @GetMapping("/")
    @ApiOperation("Get all companies")
    fun getAll(): List {
        logger.info("Get all companies")
        val companies = companyService.getAllSortedByField("n")
        logger.info(companies.toString())
        return companies
    }
}

возвращающий JSON со списком объектов. Получение списка от сервиса:

$ http :8980/vacancy/api/company/
HTTP/1.1 200
Content-Type: application/json

[
    {"n": -1, "name": "-"},
    {"n": 1, "name": "COMPANY_1"},
    {"n": 2, "name": "COMPANY_2"},
    {"n": 3, "name": "3_COMPANY"}
]

JSON неправильный. Правильно будет как-то так:

{
    "companies": [
        {"n": -1, "name": "-"},
        {"n": 1, "name": "COMPANY_1"},
        {"n": 2, "name": "COMPANY_2"},
        {"n": 3, "name": "3_COMPANY"}
    ]
}

Тем не менее, нужно тестировать. Показаны примеры для Jackson и Gson. Интеграционный тест:

package ru.perm.v.vacancy.service

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
import com.fasterxml.jackson.module.kotlin.readValue
import com.google.gson.Gson
import com.google.gson.reflect.TypeToken
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Test
import org.slf4j.LoggerFactory
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.beans.factory.annotation.Value
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.test.context.ActiveProfiles
import org.springframework.web.client.RestTemplate
import ru.perm.v.vacancy.dto.CompanyDto

/**
 * Test with projectRestTemplate
 */
@SpringBootTest
@ActiveProfiles("dev")
class RestTemplateForServicesTest {
    @Autowired
    val projectRestTemplate: ProjectRestTemplate? = null

    @Value("\${myconfig.remoteHost}")
    val remoteHost: String? = null

    private val logger = LoggerFactory.getLogger(this.javaClass.name)

    @Test
    fun getMyConfigRemoteHost() {
        assertEquals("http://127.0.0.1:8980/vacancy/api", remoteHost)
    }

    @Test
    fun getByN_WithProjectRestTemplate() {
        val company = projectRestTemplate?.getForObjectCompany(remoteHost + "/company/1")

        assertEquals(CompanyDto(1, "COMPANY_1"), company)
    }

    @Test
    fun getAllCheckBody_WithProjectRestTemplateAndGson() {
        val json = RestTemplate().getForEntity(remoteHost + "/company/", String::class.java).body
        val typeToken = object : TypeToken<kotlin.collections.List>() {}.type
        val companies = Gson().fromJson<List>(json, typeToken)

        assertEquals(4, companies.size)
        assertEquals(CompanyDto(-1L, "-"), companies[0])
        assertEquals(CompanyDto(1, "COMPANY_1"), companies[1])
        assertEquals(CompanyDto(2, "COMPANY_2"), companies.get(2))
        assertEquals(CompanyDto(3, "3_COMPANY"), companies.get(3))
    }

    @Test
    fun getAllCheckBody_WithProjectRestTemplateAsReceiveStringToJackson() {

        val jacksonMapper = jacksonObjectMapper()
        val json = RestTemplate().getForEntity(remoteHost + "/company/", String::class.java).body
        val companies: List = jacksonMapper.readValue(json)

        assertEquals(4, companies.size)
        assertEquals(CompanyDto(-1L, "-"), companies[0])
        assertEquals(CompanyDto(1, "COMPANY_1"), companies[1])
        assertEquals(CompanyDto(2, "COMPANY_2"), companies.get(2))
        assertEquals(CompanyDto(3, "3_COMPANY"), companies.get(3))
    }

    // received LinkedHashMap
    @Test
    fun getAllCheckBody_WithProjectRestTemplateAndJacksonAndBodyAsArray() {
        val response = RestTemplate().getForEntity(remoteHost + "/company/", Array::class.java).body
        assertEquals(4, response.size)
        assertEquals(java.util.LinkedHashMap::class.java, response[0]!!.javaClass)
    }

    @Test
    fun getAllCheckBody_WithProjectRestTemplateAndJacksonAndBodyConvert() {
        val jsonString = RestTemplate().getForEntity(remoteHost + "/company/",
            String::class.java).body
        val mapper = ObjectMapper()
        // convert to LIST with TYPE CompanyDto
        val type = mapper.getTypeFactory().constructParametricType(
            List::class.java, CompanyDto::class.java);
        val companies = mapper.readValue<List>(jsonString, type)

        assertEquals(4, companies.size)
        assertEquals(CompanyDto(-1L, "-"), companies[0])
        assertEquals(CompanyDto(1, "COMPANY_1"), companies[1])
        assertEquals(CompanyDto(2, "COMPANY_2"), companies.get(2))
        assertEquals(CompanyDto(3, "3_COMPANY"), companies.get(3))
    }

    // Оставлен для примера где может появиться  LinkedHashMap
    @Test
    fun getAllCheckBody_WithProjectRestTemplate() {
        val response = RestTemplate().getForEntity(remoteHost + "/company/",
            Array::class.java).body
        assertEquals(4, response.size)
        assertEquals(java.util.LinkedHashMap::class.java, response[0]!!.javaClass)
    }
}

Еще пример:


package ru.perm.v.vacancy.service

import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.beans.factory.annotation.Value
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.test.context.ActiveProfiles
import org.springframework.web.client.RestTemplate
import ru.perm.v.vacancy.dto.CompanyDto

@SpringBootTest
@ActiveProfiles("test")
class ProjectRestTemplateIntegrationTest {
    @Value("\${myconfig.remoteHost}")
    val remoteHost: String? = null

    @Autowired
    lateinit var projectRestTemplate: ProjectRestTemplate

    @Test
    fun checkRemoteHostValue() {
        assertEquals("http://127.0.0.1:8980/vacancy/api", remoteHost)
    }

    @Test
    fun checkWorkRestTemplate() {
        val COMPANY_N = 1L
        val companyDTO = projectRestTemplate?.getForObjectCompany("http://127.0.0.1:8980/vacancy/api/company/${COMPANY_N}")

        assert(companyDTO != null)
        assertEquals(CompanyDto(COMPANY_N, "COMPANY_1"), companyDTO)
    }

    @Test
    fun forEntity() {
        val url = "http://127.0.0.1:8980/vacancy/api/company/1"

        val company = RestTemplate().getForEntity(url, CompanyDto::class.java).body as CompanyDto

        assertEquals(1, company.n)
    }

    @Test
    fun forResponseEntity() {
        val url = "http://127.0.0.1:8980/vacancy/api/company/1"

      val responseEntity = RestTemplate().getForEntity(url, CompanyDto::class.java)

        assertEquals(CompanyDto(1,"COMPANY_1"), responseEntity.body)
    }

    @Test
    fun forList() {
        val url = "http://127.0.0.1:8980/vacancy/api/company/"
        val companies = RestTemplate().getForEntity(url, List::class.java).body as List

        assertEquals(4, companies.size)
    }


Ссылки:
Примеры для Kotlin конвертирования из JSON списка объектов

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