BAEL-5737: Fix the JsonMappingException: Can not deserialize instance of java.util.ArrayList (#13837)

jackson-modules/jackson-exceptions/src/main/java/com/baeldung/mappingexception/Country.java

@@ -0,0 +1,26 @@
+package com.baeldung.mappingexception;
+
+import java.util.List;
+
+public class Country {
+
+    private String name;
+    private List<String> cities;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getCities() {
+        return cities;
+    }
+
+    public void setCities(List<String> cities) {
+        this.cities = cities;
+    }
+
+}

jackson-modules/jackson-exceptions/src/test/java/com/baeldung/mappingexception/JacksonMappingExceptionUnitTest.java

@@ -1,34 +1,33 @@
 package com.baeldung.mappingexception;
 
 import static org.hamcrest.Matchers.containsString;
-import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
 
-import java.io.IOException;
-import java.util.List;
 import org.junit.Test;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
-import com.fasterxml.jackson.core.JsonGenerationException;
+import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.core.JsonParseException;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.module.SimpleModule;
-import com.google.common.collect.Lists;
 
 public class JacksonMappingExceptionUnitTest {
 
     @Test(expected = JsonMappingException.class)
-    public final void givenObjectHasNoAccessors_whenSerializing_thenException() throws JsonParseException, IOException {
+    public void givenObjectHasNoAccessors_whenSerializing_thenException() throws JsonProcessingException {
         final String dtoAsString = new ObjectMapper().writeValueAsString(new MyDtoNoAccessors());
 
         assertThat(dtoAsString, notNullValue());
     }
 
     @Test
-    public final void givenObjectHasNoAccessors_whenSerializingWithPrivateFieldsVisibility_thenNoException() throws JsonParseException, IOException {
+    public void givenObjectHasNoAccessors_whenSerializingWithPrivateFieldsVisibility_thenNoException() throws JsonProcessingException {
         final ObjectMapper objectMapper = new ObjectMapper();
         objectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
         final String dtoAsString = objectMapper.writeValueAsString(new MyDtoNoAccessors());
@@ -39,7 +38,7 @@ public class JacksonMappingExceptionUnitTest {
     }
 
     @Test
-    public final void givenObjectHasNoAccessorsButHasVisibleFields_whenSerializing_thenNoException() throws JsonParseException, IOException {
+    public void givenObjectHasNoAccessorsButHasVisibleFields_whenSerializing_thenNoException() throws JsonProcessingException {
         final ObjectMapper objectMapper = new ObjectMapper();
         final String dtoAsString = objectMapper.writeValueAsString(new MyDtoNoAccessorsAndFieldVisibility());
 
@@ -48,4 +47,30 @@ public class JacksonMappingExceptionUnitTest {
         assertThat(dtoAsString, containsString("booleanValue"));
     }
 
+    @Test
+    public void givenJsonWithInvalidList_whenDeserializing_thenThrowException() throws JsonProcessingException {
+        final String json = "{\"name\":\"Netherlands\",\"cities\":{\"Amsterdam\", \"Tamassint\"}}";
+        final ObjectMapper mapper = new ObjectMapper();
+
+        Exception exception = assertThrows(JsonMappingException.class, () -> mapper.reader()
+            .forType(Country.class)
+            .readValue(json));
+
+        assertTrue(exception.getMessage()
+            .contains("Cannot deserialize value of type `java.util.ArrayList<java.lang.String>`"));
+    }
+
+    @Test
+    public void givenJsonWithValidList_whenDeserializing_thenCorrect() throws JsonProcessingException {
+        final String json = "{\"name\":\"Netherlands\",\"cities\":[\"Amsterdam\", \"Tamassint\"]}";
+        final ObjectMapper mapper = new ObjectMapper();
+
+        Country country = mapper.reader()
+            .forType(Country.class)
+            .readValue(json);
+
+        assertEquals("Netherlands", country.getName());
+        assertEquals(Arrays.asList("Amsterdam", "Tamassint"), country.getCities());
+    }
+
 }