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Jackson module
that adds support for accessing parameter names; a feature added in JDK 8.
## Usage
### Maven dependency
For maven dependency definition, click on the second badge in the previous, Status section.
### Registering module
Like all standard Jackson modules (libraries that implement Module interface), registration is done as follows:
```java
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new ParameterNamesModule());
```
after which functionality is available for all normal Jackson operations.
### Delegating creator
By default, Jackson uses single argument constructors for mapping whole JSON value into value of the argument.
To override this behavior use the `ParameterNamesModule` constructor with `JsonCreator.Mode` parameter.
For example, to use same behavior as for constructors with multiple parameters:
```java
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new ParameterNamesModule(JsonCreator.Mode.PROPERTIES));
```
### Usage example
Java 8 API adds support for accessing parameter names at runtime in order to enable clients to abandon the JavaBeans standard if they want to without forcing them to use annotations (such as [JsonProperty][1]).
So, after registering the module as described above, you will be able to use data binding with a class like
```java
class Person {
// mandatory fields
private final String name;
private final String surname;
// optional fields
private String nickname;
// no annotations are required if preconditions are met (details below)
public Person(String name, String surname) {
this.name = name;
this.surname = surname;
}
public String getName() {
return name;
}
public String getSurname() {
return surname;
}
public String getNickname() {
return nickname;
}
public void setNickname(String nickname) {
this.nickname = nickname;
}
}
```
Preconditions:
- class Person must be compiled with Java 8 compliant compiler with option to store formal parameter names turned on (`-parameters` option). For more information about Java 8 API for accessing parameter names at runtime see [this][2]
- if there are multiple visible constructors and there is no default constructor, `@JsonCreator` is required to select constructor for deserialization
- if used with `jackson-databind` lower than `2.6.0`, `@JsonCreator` is required. In practice, `@JsonCreator` is also often required with `2.6.0+` due to issues with constructor discovery that will be resolved in `2.7`.
- if class Person has a single argument constructor, its argument needs to be annotated with `@JsonProperty("propertyName")`. This is to preserve legacy behavior, see [FasterXML/jackson-databind/#1498][3]
## More
See [Wiki](../../wiki) for more information (javadocs, downloads).
[1]: http://jackson.codehaus.org/1.1.2/javadoc/org/codehaus/jackson/annotate/JsonProperty.html
[2]: http://docs.oracle.com/javase/tutorial/reflect/member/methodparameterreflection.html
[3]: https://github.com/FasterXML/jackson-databind/issues/1498
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