I am trying to write a custom JSON deserializer in Spring. I want to use default serializer for most part of fields and use a custom deserializer for few properties. Is it possible? I am trying this way because, most part of properties are values, so for these I can let Jackson use default deserializer; but few properties are references, so in the custom deserializer I have to query a database for reference name and get reference value from database.
I'll show some code if needed.
This question is related to
java
json
spring
jackson
deserialization
I've searched a lot and the best way I've found so far is on this article:
Class to serialize
package net.sghill.example;
import net.sghill.example.UserDeserializer
import net.sghill.example.UserSerializer
import org.codehaus.jackson.map.annotate.JsonDeserialize;
import org.codehaus.jackson.map.annotate.JsonSerialize;
@JsonDeserialize(using = UserDeserializer.class)
public class User {
private ObjectId id;
private String username;
private String password;
public User(ObjectId id, String username, String password) {
this.id = id;
this.username = username;
this.password = password;
}
public ObjectId getId() { return id; }
public String getUsername() { return username; }
public String getPassword() { return password; }
}
Deserializer class
package net.sghill.example;
import net.sghill.example.User;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.ObjectCodec;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;
import java.io.IOException;
public class UserDeserializer extends JsonDeserializer<User> {
@Override
public User deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
ObjectCodec oc = jsonParser.getCodec();
JsonNode node = oc.readTree(jsonParser);
return new User(null, node.get("username").getTextValue(), node.get("password").getTextValue());
}
}
Edit: Alternatively you can look at this article which uses new versions of com.fasterxml.jackson.databind.JsonDeserializer.
With Spring MVC 4.2.1.RELEASE, you need to use the new Jackson2 dependencies as below for the Deserializer to work.
Dont use this
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.12</version>
</dependency>
Use this instead.
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.2.2</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.2.2</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.2.2</version>
</dependency>
Also use com.fasterxml.jackson.databind.JsonDeserializer and com.fasterxml.jackson.databind.annotation.JsonDeserialize for the deserialization and not the classes from org.codehaus.jackson
I was trying to @Autowire a Spring-managed service into my Deserializer. Somebody tipped me off to Jackson using the new operator when invoking the serializers/deserializers. This meant no auto-wiring of Jackson's instance of my Deserializer. Here's how I was able to @Autowire my service class into my Deserializer:
context.xml
<mvc:annotation-driven>
<mvc:message-converters>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="objectMapper" ref="objectMapper" />
</bean>
</mvc:message-converters>
</mvc>
<bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
<!-- Add deserializers that require autowiring -->
<property name="deserializersByType">
<map key-type="java.lang.Class">
<entry key="com.acme.Anchor">
<bean class="com.acme.AnchorDeserializer" />
</entry>
</map>
</property>
</bean>
Now that my Deserializer is a Spring-managed bean, auto-wiring works!
AnchorDeserializer.java
public class AnchorDeserializer extends JsonDeserializer<Anchor> {
@Autowired
private AnchorService anchorService;
public Anchor deserialize(JsonParser parser, DeserializationContext context)
throws IOException, JsonProcessingException {
// Do stuff
}
}
AnchorService.java
@Service
public class AnchorService {}
Update: While my original answer worked for me back when I wrote this, @xi.lin's response is exactly what is needed. Nice find!
Source: Stackoverflow.com