The Configure() Method in Jackson in JSON
In this tutorial, learn how to use the configure() method in Jackson in JSON. Read on to see how this tutorial can help you!
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Join For FreeConfigure method allows you to add additional behavior for ObjectMapper.
1. #configure(JsonParser.Feature, boolean):
| Feature name | Description | Default Value |
|---|---|---|
| AUTO_CLOSE_SOURCE | Will automatically close passed InputStream or Reader | true |
| ALLOW_COMMENTS | Allow using of Java/C++ style comments in JSON. | false |
| ALLOW_YAML_COMMENTS | Allows using of YAML-style comments in JSON. | false |
| ALLOW_UNQUOTED_FIELD_NAMES | Allows to write fields without quotes | false |
| ALLOW_SINGLE_QUOTES | Allows using apostrophe, character '\'' instead of the standard quotes | false |
| STRICT_DUPLICATE_DETECTION | Throw exception if duplicated field found | false |
| IGNORE_UNDEFINED | Used in case if no definition is found for a property that input content contains. Has no effect in the case of JSON parsing | false |
| INCLUDE_SOURCE_IN_LOCATION | Include source reference information in JsonLocation. If the feature is disabled prints UNKNOWN location | true |
Java:
public class StrictDuplicateMapper {
public static void main(String[] args) throws JsonProcessingException {
String json = "{" +
"\"name\":\"Ali Z\", " +
"\"name\":\"Ali Zh\"" + // will throw exception because that field is duplicated
"}";
ObjectMapper mapper = new ObjectMapper()
.configure(JsonParser.Feature.STRICT_DUPLICATE_DETECTION, true)
.enable(JsonParser.Feature.STRICT_DUPLICATE_DETECTION);// another way of enabling featur
mapper.readValue(json, Person.class);
}
public static class Person {
private String name;
@JsonCreator
public Person(@JsonProperty("name") String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
}
2. ObjectMapper#configure(JsonGenerator.Feature, boolean):
| Feature name | Description | Default value |
|---|---|---|
| AUTO_CLOSE_TARGET | Will automatically close passed InputStream or Reader | true |
| AUTO_CLOSE_JSON_CONTENT | Determines what to do with JsonToken.START_ARRAY or JsonToken.START_OBJECT if the generator is closed. If enabled, such elements are automatically closed; if disabled, nothing specific is done | true |
| FLUSH_PASSED_TO_STREAM | if enabled calling JsonGenerator#flush will have the same effect as flush() in OutputStream or Writer | true |
| WRITE_BIGDECIMAL_AS_PLAIN | Will write BigDecimal as plain text using the BigDecimal.toPlainString() | false |
| STRICT_DUPLICATE_DETECTION | Throw exception if duplicated field found | false |
| IGNORE_UNKNOWN | Will throw JsonProcessingException if there is no information about the required field. Has no effect when serializing JSON. | false |
Java:
public class JsonGeneratorExample {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper()
.configure(JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN, true);
Person person = new Person();
person.setAge(BigDecimal.valueOf(12334535345456700.12345634534534578901));
String json = mapper.writeValueAsString(person);
System.out.println(json);
}
public static class Person {
private BigDecimal age;
public BigDecimal getAge() {
return age;
}
public void setAge(BigDecimal age) {
this.age = age;
}
}
}
3. ObjectMapper#configure(SerializationFeature, boolean):
| Feature name | Description | Default value |
|---|---|---|
| WRAP_ROOT_VALUE | if enabled will wrap root value. The feature is mostly intended for JAXB compatibility. if disabled JSON will look like that: {"name":"Ali Z"}if enabled JSON will look like that: {"Person":{"name":"Ali Z"}} |
false |
| INDENT_OUTPUT | Will indent output JSON string. if disabled JSON will look like that: {"name":"Ali Z"}if enabled JSON will look like that: {
"name" : "Ali Z"
} |
false |
| FAIL_ON_EMPTY_BEANS | Will throw an exception in the case there are no accessors for fields like getters. | true |
| FAIL_ON_SELF_REFERENCES | Will throw a Jackson-specific exception if direct self-reference is detected in a POJO object. Pay attention in case if it's disabled it may throw StackOverflowError | true |
| WRAP_EXCEPTIONS | If enabled, Jackson will catch exceptions are thrown during serialization and wrap it with Jackson exception by providing additional information. If disabled will throw the original exception. | false |
| FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS | Will throw an exception, In case the object has type information but it was marked with @JsonUnwrapped. if disabled type information will be ignored | true |
| WRITE_SELF_REFERENCES_AS_NULL | Writes self-directed references as null. Pay attention that SerializationFeature.FAIL_ON_SELF_REFERENCES configuration is disabled. | false |
| CLOSE_CLOSEABLE | if enabled, will close() stream passed to writeValue. if you want to disable that feature also pay attention to JsonGenerator.Feature.AUTO_CLOSE_TARGET configuration | false |
| WRITE_DATES_AS_TIMESTAMPS | if enabled, Jackson will serialize java.util.Date(also subtype) used as a key in a Map will be serialized as a timestamp. if disable, will serialized using ISO-8601 (example: 2021-06-20T10:22:34.364+00:00) | false |
| WRITE_DATES_WITH_ZONE_ID | if enabled, includes timezone information. For example: 2011-12-03T10:15:30+01:00[Europe/Paris] |
false |
| WRITE_CHAR_ARRAYS_AS_JSON_ARRAYS | If enabled will wright char[] as JSON arrays, {"surname":["Z","h","a","g","p","a","r","o","v"]}if disabled will write it as a son string {"surname":"Zhagparov"} |
false |
| WRITE_ENUMS_USING_TO_STRING | These two configurations configure the way enums will be serialized into JSON. If WRITE_ENUMS_USING_TO_STRING is enabled and WRITE_ENUMS_USING_INDEX is disabled, it will serialize enums using toString() {"permissionEnum":"ADMIN"} |
false |
| WRITE_ENUMS_USING_INDEX | If WRITE_ENUMS_USING_TO_STRING is disabled and WRITE_ENUMS_USING_INDEX is enabled, it will serialize enums using Enum.ordinal() {"permissionEnum":0} |
false |
| WRITE_ENUM_KEYS_USING_INDEX | If enabled, it will serialize enums used in Map as key using Enum.ordinal() {"permissionEnum":{"0":"admin"}}If disabled, it will serialize enums using Enum.toString() {"permissionEnum":{"ADMIN":"admin"}} |
false |
| WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED | If enabled, won't convert List with one element into JSON array {"stringList":"Ali Z"}If disabled, it will convert List with one element into JSON array {"stringList":["Ali Z"]} |
false |
| WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS | if enabled, will write date timestamps in nanoseconds. {"date":[2021,6,20,14,16,48,260]}if disabled, {"date":[2021,6,20,14,17,12,990000000]} |
true |
| ORDER_MAP_ENTRIES_BY_KEYS | if enabled, will sort Map entries by key before serialization. Won't perform sorting, if disabled. | false |
| EAGER_SERIALIZER_FETCH | if enabled, ObjectWriter will try to eagerly fetch the necessary JsonSerializer-s. | true |
| USE_EQUALITY_FOR_OBJECT_ID | if enabled, will use Object.equal() method as an object identity. if disabled, will use true JVM-level identity as an object identity. |
false |
Java:
public class JsonSerializationFeatureExample {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper()
.configure(SerializationFeature.WRAP_ROOT_VALUE, true)
.configure(SerializationFeature.INDENT_OUTPUT, true);
Person person = new Person();
person.setName("Ali Z");
String json = mapper.writeValueAsString(person);
System.out.println(json);
}
public static class Person {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
}4. ObjectMapper#configure(DeserializationFeature, boolean):
| Feature name | Description | Default value |
|---|---|---|
| USE_BIG_DECIMAL_FOR_FLOATS | if enabled and the field type is Object or Number it will deserialize floating-point numbers as BigDecimal; if disabled, it will be deserialized as Double. | false |
| USE_BIG_INTEGER_FOR_INTS | if enabled and the field type is Object or Number it will deserialize non-floating-point numbers as BigInteger. if disabled, the most compact variant will be used. | false |
| USE_LONG_FOR_INTS | if enabled and the field type is Object or Number it will deserialize non-floating-point numbers as Long; if disabled, the most compact variant will be used. | false |
| USE_JAVA_ARRAY_FOR_JSON_ARRAY | if enabled and the field type is unknown for example Object, Jackson will deserialize JSON array as Object[]; if disabled, will deserialize as List<Object> | false |
| FAIL_ON_UNKNOWN_PROPERTIES | if enabled, Jackson will throw an exception if the unknown property is found. if disabled will ignore such a field. | true |
| FAIL_ON_NULL_FOR_PRIMITIVES | if enabled, Jackson will throw an exception if JSON contains a null value for the primitive type. if disabled default values (like 0.0, 0, etc.) will be used. | false |
| FAIL_ON_NUMBERS_FOR_ENUMS | if enabled, Jackson will throw an exception if JSON contains a number value for the enum. if disabled such value will be matched with Enum.ordinal() | false |
| FAIL_ON_READING_DUP_TREE_KEY | if enabled, will fail if find a duplicated tree key. if disabled, no exception is thrown and the later value overwrites the earlier value. | false |
| FAIL_ON_IGNORED_PROPERTIES | if enabled and JSON contains values that are explicitly marked as ignorable, will be thrown an exception. if disabled, such fields will be ignored. | false |
| FAIL_ON_MISSING_CREATOR_PROPERTIES | if enable, Jackson will throw an exception if JSON data field doesn't describe in POJO. If disabled will set null for unknown fields. | false |
| FAIL_ON_NULL_CREATOR_PROPERTIES | If enabled, will throw an exception if one or more field was passed as null to the constructor or static factory method. will ignore such cases, if disabled. | false |
| WRAP_EXCEPTIONS | If enabled, Jackson will catch exceptions are thrown during deserialization and wrap it with Jackson exception by providing additional information. If disabled will throw the original exception. | true |
| ACCEPT_SINGLE_VALUE_AS_ARRAY | if enable Jackson will accept a single value as an array. If disabled, then the exception will be thrown. | false |
| UNWRAP_SINGLE_VALUE_ARRAYS | If enabled, it will unwrap a single value array and deserialize it into the corresponding datatype. If disabled, the exception will be thrown. | false |
| UNWRAP_ROOT_VALUE | If enabled, it will unwrap the root value. It means it will accept such JSON {"Person":{"name":"Ali Z"}}as {"name":"Ali Z"} |
false |
| ACCEPT_EMPTY_STRING_AS_NULL_OBJECT | If enabled, Jackson won't fail in case there is a mismatch with POJO field data type, for empty String public static class Person {
private Integer age;
}and JSON looks like that {"age":""}Jackson will set null instead of throwing an exception. |
false |
| ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT | If enabled, Jackson won't fail in case there is a mismatch with POJO field data type, for empty String public static class Person {
private Integer age;
}and JSON looks like that {"age":[]}Jackson will set null instead of throwing an exception. |
false |
| ACCEPT_FLOAT_AS_INT | if enabled, will convert floating-point numbers into a non-floating-point numbers (like Long, long, int, etc.) by truncating numbers. | true |
| READ_ENUMS_USING_TO_STRING | If enabled, it will deserialize Enum using to string. if disabled, will use Enum.ordinal(); | false |
| READ_UNKNOWN_ENUM_VALUES_AS_NULL | If enabled, it will deserialize the unknown enum value as null. If disabled will throw an exception. | false |
| READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE | If enabled, it will set to unknown enum value predefined with @JsonEnumDefaultValue value. If disabled, it will throw an exception. | false |
| READ_DATE_TIMESTAMPS_AS_NANOSECONDS | If enabled, Jackson will expect that timestamp written in nanoseconds. If disabled, timestamp expected in milliseconds. | true |
| ADJUST_DATES_TO_CONTEXT_TIME_ZONE | If enabled, it will adjust a date property timezone. if disabled, will only adjust if the value doesn't contain a time zone by itself. | true |
Java:
public class DeserializeExample {
public static void main(String[] args) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper()
.configure(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES, true)
.enable(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES);
Person person = mapper.readValue("{}", Person.class);
}
public static class Person {
private Integer age;
@JsonCreator
public Person(@JsonProperty("age") Integer age) {
this.age = age;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Person{" +
"age=" + age +
'}';
}
}
}
JSON
Jackson (API)
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