Bael 4457 list of json objects with rest template (#10058)

* Add users.json

* BAEL-4457 demo app with Object array and ParameterizedTypeReference example

* BAEL-4457 write unit tests

* BAEL-4456 remove new directory

* BAEL-4457 fix pom and testname

* BAEL-4457 use default target release

* BAEL-4457 add more examples of processing the objects and address comments

* BAEL-4457 remove new ArrayList and put @ResponseBody before public

* BAEL-4457 use static userJson object

* BAEL-4456 tidy up extra spaces

* BAEL-4457 removed too many brackets

* BAEL-4457 remove incorrect assertion

* BAEL-4457 use a service instead of another controller

* BAEL-4457 use ObjectMapper to extract usernames from objects

* BAEL-4457 fix UserController

* BAEL-4457 delete provider service and controller

* BAEL-4457 use functional interface where possible

* BAEL-4457 remove unnecessary annotations and tidy indents for exchange()

* BAEL-4457 use @JsonCreator and @JsonProperty and resolve comments

* BAEL-4457 improve comment

* BAEL-4457 remove comments and use assertj core lib for assertions

* BAEL-4457 fix indents

Co-authored-by: Trixi Turny <writetotrixi@gmail.com>

spring-resttemplate-2/pom.xml

@@ -71,16 +71,16 @@
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
         </dependency>
-        
+
     </dependencies>
-    
+
     <build>
         <plugins>
-        <plugin>
+            <plugin>
-            <groupId>org.springframework.boot</groupId>
+                <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-maven-plugin</artifactId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
-        </plugin>
+            </plugin>
         </plugins>
     </build>
 
-</project>
+</project>

spring-resttemplate-2/src/main/java/com/baeldung/resttemplate/json/consumer/service/UserConsumerService.java

@@ -0,0 +1,16 @@
+package com.baeldung.resttemplate.json.consumer.service;
+
+import java.util.List;
+
+public interface UserConsumerService {
+
+    List<String> processUserDataFromObjectArray();
+
+    List<String> processUserDataFromUserArray();
+
+    List<String> processUserDataFromUserList();
+
+    List<String> processNestedUserDataFromUserArray();
+
+    List<String> processNestedUserDataFromUserList();
+}

spring-resttemplate-2/src/main/java/com/baeldung/resttemplate/json/consumer/service/UserConsumerServiceImpl.java

@@ -0,0 +1,90 @@
+package com.baeldung.resttemplate.json.consumer.service;
+
+import com.baeldung.resttemplate.json.model.Address;
+import com.baeldung.resttemplate.json.model.User;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.client.RestTemplate;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class UserConsumerServiceImpl implements UserConsumerService {
+
+    private static final String BASE_URL = "http://localhost:8080/users";
+    private final RestTemplate restTemplate;
+    private static final ObjectMapper mapper = new ObjectMapper();
+
+    public UserConsumerServiceImpl(RestTemplate restTemplate) {
+        this.restTemplate = restTemplate;
+    }
+
+    @Override
+    public List<String> processUserDataFromObjectArray() {
+        ResponseEntity<Object[]> responseEntity = restTemplate.getForEntity(BASE_URL, Object[].class);
+        Object[] objects = responseEntity.getBody();
+        return Arrays.stream(objects)
+          .map(object -> mapper.convertValue(object, User.class))
+          .map(User::getName)
+          .collect(Collectors.toList());
+    }
+
+    @Override
+    public List<String> processUserDataFromUserArray() {
+        ResponseEntity<User[]> responseEntity = restTemplate.getForEntity(BASE_URL, User[].class);
+        User[] userArray = responseEntity.getBody();
+        return Arrays.stream(userArray)
+          .map(User::getName)
+          .collect(Collectors.toList());
+    }
+
+    @Override
+    public List<String> processUserDataFromUserList() {
+        ResponseEntity<List<User>> responseEntity =
+          restTemplate.exchange(
+            BASE_URL,
+            HttpMethod.GET,
+            null,
+            new ParameterizedTypeReference<List<User>>() {}
+          );
+        List<User> users = responseEntity.getBody();
+        return users.stream()
+          .map(User::getName)
+          .collect(Collectors.toList());
+    }
+
+    @Override
+    public List<String> processNestedUserDataFromUserArray() {
+        ResponseEntity<User[]> responseEntity = restTemplate.getForEntity(BASE_URL, User[].class);
+        User[] userArray = responseEntity.getBody();
+        //we can get more info if we need :
+        MediaType contentType = responseEntity.getHeaders().getContentType();
+        HttpStatus statusCode = responseEntity.getStatusCode();
+
+        return Arrays.stream(userArray)
+          .flatMap(user -> user.getAddressList().stream())
+          .map(Address::getPostCode)
+          .collect(Collectors.toList());
+    }
+
+    @Override
+    public List<String> processNestedUserDataFromUserList() {
+        ResponseEntity<List<User>> responseEntity =
+          restTemplate.exchange(
+            BASE_URL,
+            HttpMethod.GET,
+            null,
+            new ParameterizedTypeReference<List<User>>() {}
+          );
+        List<User> userList = responseEntity.getBody();
+        return userList.stream()
+          .flatMap(user -> user.getAddressList().stream())
+          .map(Address::getPostCode)
+          .collect(Collectors.toList());
+    }
+}

spring-resttemplate-2/src/main/java/com/baeldung/resttemplate/json/model/Address.java

@@ -0,0 +1,29 @@
+package com.baeldung.resttemplate.json.model;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+
+@JsonInclude(JsonInclude.Include.NON_NULL)
+public class Address {
+    private final String addressLine1;
+    private final String addressLine2;
+    private final String town;
+    private final String postCode;
+
+    @JsonCreator
+    public Address(
+      @JsonProperty("addressLine1") String addressLine1,
+      @JsonProperty("addressLine2") String addressLine2,
+      @JsonProperty("town") String town,
+      @JsonProperty("postCode") String postCode) {
+        this.addressLine1 = addressLine1;
+        this.addressLine2 = addressLine2;
+        this.town = town;
+        this.postCode = postCode;
+    }
+    public String getPostCode() {
+        return postCode;
+    }
+}

spring-resttemplate-2/src/main/java/com/baeldung/resttemplate/json/model/User.java

@@ -0,0 +1,30 @@
+package com.baeldung.resttemplate.json.model;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.List;
+
+@JsonInclude(JsonInclude.Include.NON_NULL)
+public class User {
+    private final int id;
+    private final String name;
+    private final List<Address> addressList;
+
+    @JsonCreator
+    public User(
+      @JsonProperty("id") int id,
+      @JsonProperty("name") String name,
+      @JsonProperty("addressList") List<Address> addressList) {
+        this.id = id;
+        this.name = name;
+        this.addressList = addressList;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public List<Address> getAddressList() { return addressList; }
+}

spring-resttemplate-2/src/test/java/com/baeldung/resttemplate/json/consumer/service/UserConsumerServiceImplUnitTest.java

@@ -0,0 +1,127 @@
+package com.baeldung.resttemplate.json.consumer.service;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.client.ExpectedCount;
+import org.springframework.test.web.client.MockRestServiceServer;
+import org.springframework.web.client.RestTemplate;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.client.match.MockRestRequestMatchers.method;
+import static org.springframework.test.web.client.match.MockRestRequestMatchers.requestTo;
+import static org.springframework.test.web.client.response.MockRestResponseCreators.withStatus;
+
+@SpringBootTest
+public class UserConsumerServiceImplUnitTest {
+
+    private static String USER_JSON = "[{\"id\":1,\"name\":\"user1\",\"addressList\":[{\"addressLine1\":\"address1_addressLine1\",\"addressLine2\":\"address1_addressLine2\",\"town\":\"address1_town\",\"postCode\":\"user1_address1_postCode\"}," +
+      "{\"addressLine1\":\"address2_addressLine1\",\"addressLine2\":\"address2_addressLine2\",\"town\":\"address2_town\",\"postCode\":\"user1_address2_postCode\"}]}," +
+      "{\"id\":2,\"name\":\"user2\",\"addressList\":[{\"addressLine1\":\"address1_addressLine1\",\"addressLine2\":\"address1_addressLine2\",\"town\":\"address1_town\",\"postCode\":\"user2_address1_postCode\"}]}]";
+
+    private MockRestServiceServer mockServer;
+    private final RestTemplate restTemplate = new RestTemplate();
+    private final UserConsumerService tested = new UserConsumerServiceImpl(restTemplate);
+
+    @Before
+    public void init() {
+        mockServer = MockRestServiceServer.createServer(restTemplate);
+    }
+
+    @Test
+    public void whenProcessUserDataAsObjects_thenOK() {
+        String url = "http://localhost:8080/users";
+        List<String> expected = Arrays.asList("user1", "user2");
+
+        mockServer.expect(ExpectedCount.once(),
+          requestTo(url))
+          .andExpect(method(HttpMethod.GET))
+          .andRespond(withStatus(HttpStatus.OK)
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(USER_JSON));
+        
+        List<String> actual = tested.processUserDataFromObjectArray();
+
+        mockServer.verify();
+        assertThat(actual).containsExactly(expected.get(0), expected.get(1));
+    }
+
+    @Test
+    public void whenProcessUserDataAsArray_thenOK() {
+        String url = "http://localhost:8080/users";
+        List<String> expected = Arrays.asList("user1", "user2");
+
+        mockServer.expect(ExpectedCount.once(),
+          requestTo(url))
+          .andExpect(method(HttpMethod.GET))
+          .andRespond(withStatus(HttpStatus.OK)
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(USER_JSON));
+
+        List<String> actual = tested.processUserDataFromUserArray();
+
+        mockServer.verify();
+        assertThat(actual).containsExactly(expected.get(0), expected.get(1));
+    }
+
+    @Test
+    public void whenProcessUserDataAsList_thenOK() {
+        String url = "http://localhost:8080/users";
+        List<String> expected = Arrays.asList("user1", "user2");
+
+        mockServer.expect(ExpectedCount.once(),
+          requestTo(url))
+          .andExpect(method(HttpMethod.GET))
+          .andRespond(withStatus(HttpStatus.OK)
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(USER_JSON));
+
+        List<String> actual = tested.processUserDataFromUserList();
+
+        mockServer.verify();
+        assertThat(actual).containsExactly(expected.get(0), expected.get(1));
+    }
+
+
+    @Test
+    public void whenProcessNestedUserDataFromArray_thenOK() {
+        String url = "http://localhost:8080/users";
+        List<String> expected = Arrays.asList("user1_address1_postCode", "user1_address2_postCode", "user2_address1_postCode");
+
+        mockServer.expect(ExpectedCount.once(),
+          requestTo(url))
+          .andExpect(method(HttpMethod.GET))
+          .andRespond(withStatus(HttpStatus.OK)
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(USER_JSON));
+
+        List<String> actual = tested.processNestedUserDataFromUserArray();
+
+        mockServer.verify();
+        assertThat(actual).containsExactly(expected.get(0), expected.get(1), expected.get(2));
+    }
+
+    @Test
+    public void whenProcessNestedUserDataFromList_thenOK() {
+        String url = "http://localhost:8080/users";
+        List<String> expected = Arrays.asList("user1_address1_postCode", "user1_address2_postCode", "user2_address1_postCode");
+
+        mockServer.expect(ExpectedCount.once(),
+                requestTo(url))
+                .andExpect(method(HttpMethod.GET))
+                .andRespond(withStatus(HttpStatus.OK)
+                   .contentType(MediaType.APPLICATION_JSON)
+                   .body(USER_JSON));
+
+        List<String> actual = tested.processNestedUserDataFromUserList();
+
+        mockServer.verify();
+        assertThat(actual).containsExactly(expected.get(0), expected.get(1), expected.get(2));
+    }
+}