I am binding a JSON response to my class using Jackson. Everything works great except when there are more fields in my JSON response than my class defines. I want Jackson to ignore the fields that do not exist in my JSON response. This is due to compatability for future versions. If I add a new field I do not want previous versions of my client to crash.
Ideas?
ObjectMapper mapper = new ObjectMapper(); // can reuse, share globally
PromoResponse promoResponse = mapper.readValue(r, PromoResponse.class);
You can put the #JsonIgnoreProperties(ignoreUnknown=true) annotation on your PromoResponse class.
I believe you would want to do something like this after you declare your mapper object:
mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
-Dan
Related
I'm trying to use Jackson in case to serialize and then deserialize an object. The object contains a field -> protected Serializable data
This is where the problem comes from - this data can come from a lot of components. That is why I'm trying to configure the Jackson ObjectMapper instead of adding annotations and changing the code (because for some of the issues I have with the serialization, like this one, I have to change like hundreds of different classes). Is there any way to tell the ObjectMapper to not use .booleanValue() on null fields.
This is how I've currently configured my ObjectMapper:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setVisibility(objectMapper.getSerializationConfig().getDefaultVisibilityChecker()
.withFieldVisibility(JsonAutoDetect.Visibility.ANY)
.withGetterVisibility(JsonAutoDetect.Visibility.NONE)
.withSetterVisibility(JsonAutoDetect.Visibility.NONE)
.withCreatorVisibility(JsonAutoDetect.Visibility.NONE));
This usually happens when your object has a property definition of type Boolean but a getter of type boolean. Ensure these types match.
I'm implementing a RESTful web service where user has to send a signed verification token along with the request so that I could ensure that the request has not been tampered by a middle man. My current implementation is as follows.
Verification token is a VerifData object serialized into a String and then hashed and encrypted.
class VerifData {
int prop1;
int prop2;
}
In my service, I put data to be serialized into an instance of VerifData and then serialize it using Jackson ObjectMapper and passed along to the verification engine along with the verification token.
VerfiData verifData = new VerifData(12345, 67890);
ObjectMapper mapper = new ObjectMapper();
String verifCodeGenerated = mapper.writeValueAsString(verifData);
But it seems that each time the application container is started, the order of properties being mapped into a string by ObjectMapper changes.
Ex: one time it would be
{"prop1":12345,"prop2":67890}
and another time it would be
{"prop2":67890,"prop1":12345}
So if client has serialized the VerifData instance as into the first String, there is 50% chance of it being failed even though it is correct.
Is there a way to get around this? Can I specify the order of properties to map by ObjectMapper (like in ascending order)? Or is there any other way to best implement this verification step. Both client and server implementations are developed by me. I use Java Security API for signing and verifying.
The annotations are useful, but can be a pain to apply everywhere. You can configure your whole ObjectMapper to work this way with
Current Jackson versions:
objectMapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
Older Jackson versions:
objectMapper.configure(SerializationConfig.Feature.SORT_PROPERTIES_ALPHABETICALLY, true);
From the Jackson Annotations documentation:
// ensure that "id" and "name" are output before other properties
#JsonPropertyOrder({ "id", "name" })
// order any properties that don't have explicit setting using alphabetic order
#JsonPropertyOrder(alphabetic=true)
The following 2 ObjectMapper configuration are required:
ObjectMapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
or
ObjectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY)
defines the property serialization order used for POJO fields
Note: does not apply to java.util.Map serialization!
and
ObjectMapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true)
or
ObjectMapper.enable(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS)
Feature that determines whether java.util.Map entries are first sorted by key before serialization
Spring Boot config example (yaml):
spring:
jackson:
mapper:
SORT_PROPERTIES_ALPHABETICALLY: true
serialization:
ORDER_MAP_ENTRIES_BY_KEYS: true
In Spring Boot you can add this behaviour globally by adding the following to your Application entry point class:
#Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.featuresToEnable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
return builder;
}
In Jackson 2.x, which you are probably using today, use:
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
If you care about looks, you may also consider SerializationFeature.INDENT_OUTPUT as well.
Note that you must serialize Maps or Objects for this to sort correctly. If you serialize a JsonNode for example (from readTree), that won't be properly indented.
Example
import com.fasterxml.jackson.databind.*;
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
String input = "{\"hello\": {\"cruel\" : \"world\"} }";
Object pojo = mapper.readValue(input, Object.class);
System.out.println(mapper.writeValueAsString(pojo));
results in:
{
"hello" : {
"cruel" : "world"
}
}
There is an easier way in Spring Boot by specifying a property (in application.properties for example:
spring.jackson.mapper.sort_properties_alphabetically=true
From Duncan McGregor's answer:
Its better to use it like this:
objectMapper.configure(SerializationConfig.Feature.SORT_PROPERTIES_ALPHABETICALLY, true);
as MapperFeature is for XMLs and comes with jackson-databind which is not required...
I discovered yet another way today in case alphabetic is not your desired sorting order. It turns out adding a #JsonProperty annotation on a field places it last when writing if the rest of the fields are not annotated. I discovered that when I wanted to specify a property name which did not conform to java naming conventions.
By Adding an index attribute you can define the order. Lowest index is placed first.
#JsonProperty(index=20)
String prop1;
#JsonProperty(index=10)
String prop2;
Would render:
{"prop2": "valueProp2", "prop1": "valueProp1"}
You can use mix-in and specify the order of properties as you like:
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
#Component
public final class ObjectMapperUtils {
private static final ObjectMapper MAPPER = new ObjectMapper();
static {
MAPPER.addMixIn(Object.class, IdFirst.class);
}
#Bean
public ObjectMapper objectMapper() {
return MAPPER;
}
#JsonPropertyOrder({"id", "...", "..."})
private abstract static class IdFirst {}
}
I realize this is an old thread, but since I was looking or an answer and landed here, some additional info could be handy for other people.
The #JsonProperty annotation I am using currently (jackson-annotations-2.11.2) accepts, besides the "value" argument, an "index" (numeric) argument that specifies the order of the fields during serialization.
Instead of using flag argument:
objectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
As #Gary Rowe mentioned, we can use Jackson2ObjectMapperBuilder to sort the properties globally.
However for this to work, you must have Jackson2ObjectMapperBuilder in your classpath. It is not part of the Jackson library.
As per this documentation, spring-web dependency has Jackson2ObjectMapperBuilder file and should be in your classpath.
#Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.featuresToEnable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
return builder;
}
You can refer to this for other possible solutions
I'm implementing a RESTful web service where user has to send a signed verification token along with the request so that I could ensure that the request has not been tampered by a middle man. My current implementation is as follows.
Verification token is a VerifData object serialized into a String and then hashed and encrypted.
class VerifData {
int prop1;
int prop2;
}
In my service, I put data to be serialized into an instance of VerifData and then serialize it using Jackson ObjectMapper and passed along to the verification engine along with the verification token.
VerfiData verifData = new VerifData(12345, 67890);
ObjectMapper mapper = new ObjectMapper();
String verifCodeGenerated = mapper.writeValueAsString(verifData);
But it seems that each time the application container is started, the order of properties being mapped into a string by ObjectMapper changes.
Ex: one time it would be
{"prop1":12345,"prop2":67890}
and another time it would be
{"prop2":67890,"prop1":12345}
So if client has serialized the VerifData instance as into the first String, there is 50% chance of it being failed even though it is correct.
Is there a way to get around this? Can I specify the order of properties to map by ObjectMapper (like in ascending order)? Or is there any other way to best implement this verification step. Both client and server implementations are developed by me. I use Java Security API for signing and verifying.
The annotations are useful, but can be a pain to apply everywhere. You can configure your whole ObjectMapper to work this way with
Current Jackson versions:
objectMapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
Older Jackson versions:
objectMapper.configure(SerializationConfig.Feature.SORT_PROPERTIES_ALPHABETICALLY, true);
From the Jackson Annotations documentation:
// ensure that "id" and "name" are output before other properties
#JsonPropertyOrder({ "id", "name" })
// order any properties that don't have explicit setting using alphabetic order
#JsonPropertyOrder(alphabetic=true)
The following 2 ObjectMapper configuration are required:
ObjectMapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
or
ObjectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY)
defines the property serialization order used for POJO fields
Note: does not apply to java.util.Map serialization!
and
ObjectMapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true)
or
ObjectMapper.enable(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS)
Feature that determines whether java.util.Map entries are first sorted by key before serialization
Spring Boot config example (yaml):
spring:
jackson:
mapper:
SORT_PROPERTIES_ALPHABETICALLY: true
serialization:
ORDER_MAP_ENTRIES_BY_KEYS: true
In Spring Boot you can add this behaviour globally by adding the following to your Application entry point class:
#Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.featuresToEnable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
return builder;
}
In Jackson 2.x, which you are probably using today, use:
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
If you care about looks, you may also consider SerializationFeature.INDENT_OUTPUT as well.
Note that you must serialize Maps or Objects for this to sort correctly. If you serialize a JsonNode for example (from readTree), that won't be properly indented.
Example
import com.fasterxml.jackson.databind.*;
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
String input = "{\"hello\": {\"cruel\" : \"world\"} }";
Object pojo = mapper.readValue(input, Object.class);
System.out.println(mapper.writeValueAsString(pojo));
results in:
{
"hello" : {
"cruel" : "world"
}
}
There is an easier way in Spring Boot by specifying a property (in application.properties for example:
spring.jackson.mapper.sort_properties_alphabetically=true
From Duncan McGregor's answer:
Its better to use it like this:
objectMapper.configure(SerializationConfig.Feature.SORT_PROPERTIES_ALPHABETICALLY, true);
as MapperFeature is for XMLs and comes with jackson-databind which is not required...
I discovered yet another way today in case alphabetic is not your desired sorting order. It turns out adding a #JsonProperty annotation on a field places it last when writing if the rest of the fields are not annotated. I discovered that when I wanted to specify a property name which did not conform to java naming conventions.
By Adding an index attribute you can define the order. Lowest index is placed first.
#JsonProperty(index=20)
String prop1;
#JsonProperty(index=10)
String prop2;
Would render:
{"prop2": "valueProp2", "prop1": "valueProp1"}
You can use mix-in and specify the order of properties as you like:
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
#Component
public final class ObjectMapperUtils {
private static final ObjectMapper MAPPER = new ObjectMapper();
static {
MAPPER.addMixIn(Object.class, IdFirst.class);
}
#Bean
public ObjectMapper objectMapper() {
return MAPPER;
}
#JsonPropertyOrder({"id", "...", "..."})
private abstract static class IdFirst {}
}
I realize this is an old thread, but since I was looking or an answer and landed here, some additional info could be handy for other people.
The #JsonProperty annotation I am using currently (jackson-annotations-2.11.2) accepts, besides the "value" argument, an "index" (numeric) argument that specifies the order of the fields during serialization.
Instead of using flag argument:
objectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
As #Gary Rowe mentioned, we can use Jackson2ObjectMapperBuilder to sort the properties globally.
However for this to work, you must have Jackson2ObjectMapperBuilder in your classpath. It is not part of the Jackson library.
As per this documentation, spring-web dependency has Jackson2ObjectMapperBuilder file and should be in your classpath.
#Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.featuresToEnable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
return builder;
}
You can refer to this for other possible solutions
In my application the JAXB output generates like:
this.marshalOut(jaxb_Object, fileOutputStream);
this is method call to the spring Object XML Mapping Marshallers that generate XML files. Now, I also like to generate JSON files after this line. Any one have idea about generating JSON output using JAXB input.
I found this example code online:
ObjectMapper mapper = new ObjectMapper();
AnnotationIntrospector introspector = new JacksonAnnotationIntrospector();
// make deserializer use JAXB annotations (only)
mapper.getDeserializationConfig().setAnnotationIntrospector(introspector);
// make serializer use JAXB annotations (only)
mapper.getSerializationConfig().setAnnotationIntrospector(introspector);
mapper.writeValue( outputStream, jaxb_object);
The setAnnotationIntrospector is deprecated, is there any other way of solving this problem?
The following works (and does not use any deprecated constructors) :
ObjectMapper mapper = new ObjectMapper();
AnnotationIntrospector introspector =
new JaxbAnnotationIntrospector(mapper.getTypeFactory());
mapper.setAnnotationIntrospector(introspector);
Specifically, this line
new JaxbAnnotationIntrospector(mapper.getTypeFactory());
uses a non-deprecated constructor. I've tested this and it successfully processes JAXB Annotations (such as #XmlTransient, in my case).
You can use jackson-module-jaxb-annotations as stated in the doc you can register a JaxbAnnotationModule module:
JaxbAnnotationModule module = new JaxbAnnotationModule();
// configure as necessary
objectMapper.registerModule(module);
Doing so you can now use both JAXB annotation and Jackson native annotation.
If you update Jackson to 2.0 it is not deprecated:
http://fasterxml.github.com/jackson-databind/javadoc/2.0.0/com/fasterxml/jackson/databind/ObjectMapper.html
You can see my configuration here (Spring):
Registrer MappingJackson2HttpMessageConverter in Spring 3.1.2 with JAXB annotations
The correct solution for me was:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setAnnotationIntrospector(new JaxbAnnotationIntrospector());
According to the Jackson javadoc:
setAnnotationIntrospector
#Deprecated
public final void setAnnotationIntrospector(AnnotationIntrospector ai)
Deprecated. Since 1.8, use either withAnnotationIntrospector(AnnotationIntrospector) or Module API instead
Method for replacing existing annotation introspector(s) with specified introspector. Since this method modifies state of configuration object directly, its use is not recommended
Did you check the method withAnnotationIntrospector(AnnotationIntrospector ai) to see wheter or not it's useful in your case?
I have question related to bean to json serialziation/deserialization using Jackson. Previously I have used GSON to do that, but now I am faced with a project that already depends on Jackson and I would prefer not to introduce new dependency if I can do with what I already have at hand.
So imagine I have a bean like:
class ExampleBean {
private String firstField;
private String secondField;
// respective getters and setters
}
And then Jackson serializes it to:
{
"firstField": "<first_field_value>",
"secondField": "<second_field_value>"
}
I am using the following code to produce the above result:
ExampleBean bean;
...
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(outStream, bean);
However I would like (am expected) to get the following serialization:
{
"first_field": "<first_field_value>",
"second_field": "<second_field_value>"
}
I have deliberately simplified my example, but I have big hierarchy of beans that I want to serialize and I want to specify that the serialized attributes should always be in snake_style (that is with underscores) and the corresponding bean fields should always be camelCased. Is there any way I can enforce such field /attribute naming policies and use them without annotating the corresponding attribute for every field?
And yes I found it (it turned out that after 2 hours of searching I had been only 30 minutes away from finding it):
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(
PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
mapper.writeValue(outStream, bean);
Hopefully this will turn out to be helpful to somebody else too.
Now CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES is the deprecated strategy use SNAKE_CASE instead
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(
PropertyNamingStrategy.SNAKE_CASE);
mapper.writeValue(outStream, bean);