ObjectMapper setSerializationInclusion(JsonInclude.Include.NON_NULL) setting is not reflected [duplicate] - java

This question already has answers here:
Excluding NullNode when serializing a Jackson JSON tree model
(3 answers)
Closed 11 months ago.
ObjectMapper still includes null values. I tried a lot of solutions found here, but nothing works. I cannot use json annotation, so my only solution is predefined setting of mapper, but this was not reflected. I thought this was due to caching of objectMapper. But my only modifies of mapper are made in Constructor. So caching would not be a problem
Dependencies:
Log4J2: 2.17.1
Fasterxml Jackson annotation: 2.13.2
Fasterxml Jackson databind: 2.13.2
Wildfly: 20.0.1
OpenJDK: 11.0.14.1
I have an objectMapper defined as global value which is instantiated in constructor. Then I have one method for building a JSON which accepts key and value. As value can by anything.
private final ObjectMapper jsonMapper;
public SomeConstructor() {
this.jsonMapper = new ObjectMapper();
this.jsonMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
this.jsonMapper.setDefaultPropertyInclusion(JsonInclude.Include.NON_NULL);
}
#Override
public void setJsonVar(String jsonVar, String jsonKey, Object values) {
// loads ObjectNode from memory if exists
ObjectNode jsonNode = getJsonVar(jsonVar);
// lazy init if ObjectNode not exists
if (jsonNode == null) {
jsonNode = jsonMapper.createObjectNode();
}
// add object
jsonNode.putPOJO(jsonKey, values);
}
Usage:
setJsonVar("var-A", "key-A", 1);
setJsonVar("var-A", "key-B", null);
print("var-a");
Expectation:
I want to avoid null values in JSON.
Expected: var-A: { "key-A":1 }
Got: var-A: { "key-A":1, "key-B":null }
Why does this happen and what can I do to work around this?

This option is applicable when serializing objects, custom objects or a Map for example, but not when working with json tree. Consider this Foo class:
public class Foo {
private String id;
private String name;
//getters and setters
}
The option to exclude nulls will work as expected with it.
Main method to illustrate it:
public class Main {
public static void main(String[] args) throws Exception {
serializeNulls();
System.out.println();
doNotSerializeNulls();
}
private static void serializeNulls() throws Exception {
ObjectMapper jsonMapper = new ObjectMapper();
Foo foo = new Foo();
foo.setId("id");
System.out.println("Serialize nulls");
System.out.println(jsonMapper.writeValueAsString(foo));
Map<String, Object> map = new LinkedHashMap<>();
map.put("key1", "val1");
map.put("key2", null);
System.out.println(jsonMapper.writeValueAsString(map));
}
private static void doNotSerializeNulls() throws Exception {
ObjectMapper jsonMapper = new ObjectMapper();
jsonMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
jsonMapper.setDefaultPropertyInclusion(JsonInclude.Include.NON_NULL);
Foo foo = new Foo();
foo.setId("id");
System.out.println("Do not serialize nulls");
System.out.println(jsonMapper.writeValueAsString(foo));
Map<String, Object> map = new LinkedHashMap<>();
map.put("key1", "val1");
map.put("key2", null);
System.out.println(jsonMapper.writeValueAsString(map));
}
}

Related

Writing JSON arrays on multiple lines using Jackson in Java [duplicate]

I am using Jackson and would like to pretty-print JSON such that each element in arrays goes to each line, like:
{
"foo" : "bar",
"blah" : [
1,
2,
3
]
}
Setting SerializationFeature.INDENT_OUTPUT true only inserts newline characters for object fields, not array elements, printing the object in this way instead:
{
"foo" : "bar",
"blah" : [1, 2, 3]
}
Does anyone know how to achieve this? Thanks!
If you don't want to extend DefaultPrettyPrinter you can also just set the indentArraysWith property externally:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
DefaultPrettyPrinter prettyPrinter = new DefaultPrettyPrinter();
prettyPrinter.indentArraysWith(DefaultIndenter.SYSTEM_LINEFEED_INSTANCE);
String json = objectMapper.writer(prettyPrinter).writeValueAsString(object);
Thanks to the helpful hints, I was able to configure my ObjectMapper with desired indentation as follows:
private static class PrettyPrinter extends DefaultPrettyPrinter {
public static final PrettyPrinter instance = new PrettyPrinter();
public PrettyPrinter() {
_arrayIndenter = Lf2SpacesIndenter.instance;
}
}
private static class Factory extends JsonFactory {
#Override
protected JsonGenerator _createGenerator(Writer out, IOContext ctxt) throws IOException {
return super._createGenerator(out, ctxt).setPrettyPrinter(PrettyPrinter.instance);
}
}
{
ObjectMapper mapper = new ObjectMapper(new Factory());
mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
}
You could extend the DefaultPrettyPrinter and override the methods beforeArrayValues(…) and writeArrayValueSeparator(…) to archieve the desired behaviour. Afterwards you have to add your new Implementation to your JsonGenerator via setPrettyPrinter(…).
Mapper can be configured (jackson-2.6) with:
ObjectMapper mapper = ...
DefaultPrettyPrinter prettyPrinter = new DefaultPrettyPrinter();
prettyPrinter.indentArraysWith(DefaultIndenter.SYSTEM_LINEFEED_INSTANCE);
mapper.setDefaultPrettyPrinter(prettyPrinter);
//use mapper
The answer thankfully provided by OP shows a way for obtain a single-array-element-per-line formatted JSON String from writeValueAsString. Based on it here a solution to write the same formatted JSON directly to a file with writeValue with less code:
private static class PrettyPrinter extends DefaultPrettyPrinter {
public static final PrettyPrinter instance = new PrettyPrinter();
public PrettyPrinter() {
_arrayIndenter = Lf2SpacesIndenter.instance;
}
}
{
ObjectMapper mapper = new ObjectMapper();
ObjectWriter writer = mapper.writer(PrettyPrinter.instance);
writer.writeValue(destFile, objectToSerialize);
}
try out JSON Generator...
API Reference
good example

How to recursively parse json value in ObjectMapper.readValue?

I'm trying to parse json strings inside a json string into an Object using Jackson ObjectMapper. But I can't find a clean way to do this.
I have a SQL table storing Lists as json strings like "[1,2,3]". And I read all columns out into a Map then tries to use objectMapper.convertValue to make into a Java Object.
So here's a quick snippet to recreate the problem. Do note I don't control how the Map is generated in the actual code.
#Data
public class Main {
private List<Integer> bar;
public static void main(String[] args) throws Exception{
ObjectMapper objectMapper = new ObjectMapper();
Map<String, Object> objectMap = new HashMap<String, Object>();
objectMap.put("bar", "[1,2,3]");
// Main foo = objectMapper.convertValue(objectMap, Main.class)
String json = objectMapper.writeValueAsString(objectMap);
Main foo = objectMapper.readValue(json, Main.class);
System.out.println(foo.getBar());
}
}
But this is not right. Instead of parsing the string, ObjectMapper tries to convert String to List directly and failed. I would expect foo.getBar() returns a List with 3 elements, but the code already failed at converting stage.
You should make "[1,2,3]" as String[] so:
"[1,2,3]".replaceAll("\\[", "").replaceAll("\\]", "").replaceAll("\\s", "").split(",")
Something like:
public static void main(String[] args) throws Exception {
ObjectMapper objectMapper = new ObjectMapper();
Map<String, Object> objectMap = new HashMap<String, Object>(){{
put("bar", "[1,2,3]".replaceAll("\\[", "")
.replaceAll("]", "")
.replaceAll("\\s", "").split(","));
}};
String json = objectMapper.writeValueAsString(objectMap);
Main foo = objectMapper.readValue(json, Main.class);
System.out.println(foo.getBar());
}
you just need to replace the "[1,2,3]" with what ever you getting it from.
Note: Not sure about the application logic

Java Jackson: parse three level JSON dynamic object structure

I'm trying to use the Java Jackson ObjectMapper to parse a three level JSON object stucture with dynamic keys. I tried the following:
public class AssetsPushManifest {
private Map<String, List<Asset>> manifest = new HashMap<>();
public void addPushManifest(Resource manifestResource) throws Exception {
ObjectMapper mapper = new ObjectMapper();
Map<String, Map<String, Asset>> manifestData = mapper.readValue(manifestResource.getInputStream(), new TypeReference<Map<String, Map<String, Asset>>>() {});
for (String requestedPathName : manifestData.keySet()) {
if (!this.manifest.containsKey(requestedPathName)) {
this.manifest.put(requestedPathName, new LinkedList());
}
List<Asset> requestedPath = this.manifest.get(requestedPathName);
for (String servePath : manifestData.get(requestedPathName).keySet()) {
Asset asset = manifestData.get(requestedPathName).get(servePath);
asset.path = servePath;
requestedPath.add(asset);
}
}
...
}
public class Asset {
public String path;
public String type;
public Integer weight;
}
}
To parse this:
{
"theme/test-theme/index.html": {
"theme/test-theme/somestyling.css": {
"type": "document",
"weight": 1
}
}
}
But it won't work, why oh why? Is it too many levels? (still Java beginner here)
The end goal is to parse the several JSON structures like above into a structure like Map> so any other ways of doing this would also be fine.
I would solve this in a different way: parse the json into a map: if you give Jackson a map as type reference, it will deserialize the JSON into multi-level map:
`Map<String, Object> manifestData = mapper.readValue(manifestResource.getInputStream(), Map.class);`
Now that the json parsing hurdle is behind us, it is easier to construct an instance of an Asset by querying the map. I would do it by adding a constructor to the Asset class:
public Asset(Map<String, Object> manifestData) {
Map<String, Object> assetData = (Map<String, Object>)manifestData.values().iterator().next(); // get the single value of the map
this.path = assetData.keySet().iterator().next();
this.type = assetData.get("type");
this.weight = assetData.get("weight");
}

How to wrap a List as top level element in JSON generated by Jackson

I am running into a problem where I am trying to include a List as the root node, but I can't seem to be able to get this. Let me explain. Let's say we have a class "TestClass"
class TestClass{
String propertyA;
}
Now, in some utility method this is what I do
String utilityMethod(){
List<TestClass> list = someService.getList();
new ObjectMapper().writeValueAsString(list);
}
The output I am trying to get in JSON is
{"ListOfTestClasses":[{"propertyA":"propertyAValue"},{"propertyA":"someOtherPropertyValue"}]}
I have tried to use
objMapper.getSerializationConfig().set(Feature.WRAP_ROOT_VALUE, true);
But, I still don't seem to get it right.
Right now, I am just creating a Map < String,TestClass > and I write that to achieve what I am trying to do, which works but clearly this is a hack. Could someone please help me with a more elegant solution? Thanks
Unfortunately, even with the WRAP_ROOT_VALUE feature enabled you still need extra logic to control the root name generated when serializing a Java collection (see this answer for details why). Which leaves you with the options of:
using a holder class to define the root name
using a map.
using a custom ObjectWriter
Here is some code illustrating the three different options:
public class TestClass {
private String propertyA;
// constructor/getters/setters
}
public class TestClassListHolder {
#JsonProperty("ListOfTestClasses")
private List<TestClass> data;
// constructor/getters/setters
}
public class TestHarness {
protected List<TestClass> getTestList() {
return Arrays.asList(new TestClass("propertyAValue"), new TestClass(
"someOtherPropertyValue"));
}
#Test
public void testSerializeTestClassListDirectly() throws Exception {
final ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true);
System.out.println(mapper.writeValueAsString(getTestList()));
}
#Test
public void testSerializeTestClassListViaMap() throws Exception {
final ObjectMapper mapper = new ObjectMapper();
final Map<String, List<TestClass>> dataMap = new HashMap<String, List<TestClass>>(
4);
dataMap.put("ListOfTestClasses", getTestList());
System.out.println(mapper.writeValueAsString(dataMap));
}
#Test
public void testSerializeTestClassListViaHolder() throws Exception {
final ObjectMapper mapper = new ObjectMapper();
final TestClassListHolder holder = new TestClassListHolder();
holder.setData(getTestList());
System.out.println(mapper.writeValueAsString(holder));
}
#Test
public void testSerializeTestClassListViaWriter() throws Exception {
final ObjectMapper mapper = new ObjectMapper();
final ObjectWriter writer = mapper.writer().withRootName(
"ListOfTestClasses");
System.out.println(writer.writeValueAsString(getTestList()));
}
}
Output:
{"ArrayList":[{"propertyA":"propertyAValue"},{"propertyA":"someOtherPropertyValue"}]}
{"ListOfTestClasses":[{"propertyA":"propertyAValue"},{"propertyA":"someOtherPropertyValue"}]}
{"ListOfTestClasses":[{"propertyA":"propertyAValue"},{"propertyA":"someOtherPropertyValue"}]}
{"ListOfTestClasses":[{"propertyA":"propertyAValue"},{"propertyA":"someOtherPropertyValue"}]}
Using an ObjectWriter is very convenient - just bare in mind that all top level objects serialized with it will have the same root name. If thats not desirable then use a map or holder class instead.
I'd expect the basic idea to be something like:
class UtilityClass {
List listOfTestClasses;
UtilityClass(List tests) {
this.listOfTestClasses = tests;
}
}
String utilityMethod(){
List<TestClass> list = someService.getList();
UtilityClass wrapper = new UtilityClass(list);
new ObjectMapper().writeValueAsString(wrapper);
}

How can I include raw JSON in an object using Jackson?

I am trying to include raw JSON inside a Java object when the object is (de)serialized using Jackson. In order to test this functionality, I wrote the following test:
public static class Pojo {
public String foo;
#JsonRawValue
public String bar;
}
#Test
public void test() throws JsonGenerationException, JsonMappingException, IOException {
String foo = "one";
String bar = "{\"A\":false}";
Pojo pojo = new Pojo();
pojo.foo = foo;
pojo.bar = bar;
String json = "{\"foo\":\"" + foo + "\",\"bar\":" + bar + "}";
ObjectMapper objectMapper = new ObjectMapper();
String output = objectMapper.writeValueAsString(pojo);
System.out.println(output);
assertEquals(json, output);
Pojo deserialized = objectMapper.readValue(output, Pojo.class);
assertEquals(foo, deserialized.foo);
assertEquals(bar, deserialized.bar);
}
The code outputs the following line:
{"foo":"one","bar":{"A":false}}
The JSON is exactly how I want things to look. Unfortunately, the code fails with an exception when attempting to read the JSON back in to the object. Here is the exception:
org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token
at [Source: java.io.StringReader#d70d7a; line: 1, column: 13] (through reference chain: com.tnal.prism.cobalt.gather.testing.Pojo["bar"])
Why does Jackson function just fine in one direction but fail when going the other direction? It seems like it should be able to take its own output as input again. I know what I'm trying to do is unorthodox (the general advice is to create an inner object for bar that has a property named A), but I don't want to interact with this JSON at all. My code is acting as a pass-through for this code -- I want to take in this JSON and send it back out again without touching a thing, because when the JSON changes I don't want my code to need modifications.
Thanks for the advice.
EDIT: Made Pojo a static class, which was causing a different error.
#JsonRawValue is intended for serialization-side only, since the reverse direction is a bit trickier to handle. In effect it was added to allow injecting pre-encoded content.
I guess it would be possible to add support for reverse, although that would be quite awkward: content will have to be parsed, and then re-written back to "raw" form, which may or may not be the same (since character quoting may differ).
This for general case. But perhaps it would make sense for some subset of problems.
But I think a work-around for your specific case would be to specify type as 'java.lang.Object', since this should work ok: for serialization, String will be output as is, and for deserialization, it will be deserialized as a Map. Actually you might want to have separate getter/setter if so; getter would return String for serialization (and needs #JsonRawValue); and setter would take either Map or Object. You could re-encode it to a String if that makes sense.
Following #StaxMan answer, I've made the following works like a charm:
public class Pojo {
Object json;
#JsonRawValue
public String getJson() {
// default raw value: null or "[]"
return json == null ? null : json.toString();
}
public void setJson(JsonNode node) {
this.json = node;
}
}
And, to be faithful to the initial question, here is the working test:
public class PojoTest {
ObjectMapper mapper = new ObjectMapper();
#Test
public void test() throws IOException {
Pojo pojo = new Pojo("{\"foo\":18}");
String output = mapper.writeValueAsString(pojo);
assertThat(output).isEqualTo("{\"json\":{\"foo\":18}}");
Pojo deserialized = mapper.readValue(output, Pojo.class);
assertThat(deserialized.json.toString()).isEqualTo("{\"foo\":18}");
// deserialized.json == {"foo":18}
}
}
I was able to do this with a custom deserializer (cut and pasted from here)
package etc;
import java.io.IOException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.TreeNode;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
/**
* Keeps json value as json, does not try to deserialize it
* #author roytruelove
*
*/
public class KeepAsJsonDeserializer extends JsonDeserializer<String> {
#Override
public String deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException {
TreeNode tree = jp.getCodec().readTree(jp);
return tree.toString();
}
}
Use it by annotating the desired member like this:
#JsonDeserialize(using = KeepAsJsonDeserializer.class)
private String value;
#JsonSetter may help. See my sample ('data' is supposed to contain unparsed JSON):
class Purchase
{
String data;
#JsonProperty("signature")
String signature;
#JsonSetter("data")
void setData(JsonNode data)
{
this.data = data.toString();
}
}
This is a problem with your inner classes. The Pojo class is a non-static inner class of your test class, and Jackson cannot instantiate that class. So it can serialize, but not deserialize.
Redefine your class like this:
public static class Pojo {
public String foo;
#JsonRawValue
public String bar;
}
Note the addition of static
Adding to Roy Truelove's great answer, this is how to inject the custom deserialiser in response to appearance of #JsonRawValue:
import com.fasterxml.jackson.databind.Module;
#Component
public class ModuleImpl extends Module {
#Override
public void setupModule(SetupContext context) {
context.addBeanDeserializerModifier(new BeanDeserializerModifierImpl());
}
}
import java.util.Iterator;
import com.fasterxml.jackson.annotation.JsonRawValue;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
public class BeanDeserializerModifierImpl extends BeanDeserializerModifier {
#Override
public BeanDeserializerBuilder updateBuilder(DeserializationConfig config, BeanDescription beanDesc, BeanDeserializerBuilder builder) {
Iterator<SettableBeanProperty> it = builder.getProperties();
while (it.hasNext()) {
SettableBeanProperty p = it.next();
if (p.getAnnotation(JsonRawValue.class) != null) {
builder.addOrReplaceProperty(p.withValueDeserializer(KeepAsJsonDeserialzier.INSTANCE), true);
}
}
return builder;
}
}
This easy solution worked for me:
public class MyObject {
private Object rawJsonValue;
public Object getRawJsonValue() {
return rawJsonValue;
}
public void setRawJsonValue(Object rawJsonValue) {
this.rawJsonValue = rawJsonValue;
}
}
So I was able to store raw value of JSON in rawJsonValue variable and then it was no problem to deserialize it (as object) with other fields back to JSON and send via my REST. Using #JsonRawValue didnt helped me because stored JSON was deserialized as String, not as object, and that was not what I wanted.
This even works in a JPA entity:
private String json;
#JsonRawValue
public String getJson() {
return json;
}
public void setJson(final String json) {
this.json = json;
}
#JsonProperty(value = "json")
public void setJsonRaw(JsonNode jsonNode) {
// this leads to non-standard json, see discussion:
// setJson(jsonNode.toString());
StringWriter stringWriter = new StringWriter();
ObjectMapper objectMapper = new ObjectMapper();
JsonGenerator generator =
new JsonFactory(objectMapper).createGenerator(stringWriter);
generator.writeTree(n);
setJson(stringWriter.toString());
}
Ideally the ObjectMapper and even JsonFactory are from the context and are configured so as to handle your JSON correctly (standard or with non-standard values like 'Infinity' floats for example).
Here is a full working example of how to use Jackson modules to make #JsonRawValue work both ways (serialization and deserialization):
public class JsonRawValueDeserializerModule extends SimpleModule {
public JsonRawValueDeserializerModule() {
setDeserializerModifier(new JsonRawValueDeserializerModifier());
}
private static class JsonRawValueDeserializerModifier extends BeanDeserializerModifier {
#Override
public BeanDeserializerBuilder updateBuilder(DeserializationConfig config, BeanDescription beanDesc, BeanDeserializerBuilder builder) {
builder.getProperties().forEachRemaining(property -> {
if (property.getAnnotation(JsonRawValue.class) != null) {
builder.addOrReplaceProperty(property.withValueDeserializer(JsonRawValueDeserializer.INSTANCE), true);
}
});
return builder;
}
}
private static class JsonRawValueDeserializer extends JsonDeserializer<String> {
private static final JsonDeserializer<String> INSTANCE = new JsonRawValueDeserializer();
#Override
public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
return p.readValueAsTree().toString();
}
}
}
Then you can register the module after creating the ObjectMapper:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JsonRawValueDeserializerModule());
String json = "{\"foo\":\"one\",\"bar\":{\"A\":false}}";
Pojo deserialized = objectMapper.readValue(json, Pojo.class);
I had the exact same issue.
I found the solution in this post :
Parse JSON tree to plain class using Jackson or its alternatives
Check out the last answer.
By defining a custom setter for the property that takes a JsonNode as parameter and calls the toString method on the jsonNode to set the String property, it all works out.
Using an object works fine both ways... This method has a bit of overhead deserializing the raw value in two times.
ObjectMapper mapper = new ObjectMapper();
RawJsonValue value = new RawJsonValue();
value.setRawValue(new RawHello(){{this.data = "universe...";}});
String json = mapper.writeValueAsString(value);
System.out.println(json);
RawJsonValue result = mapper.readValue(json, RawJsonValue.class);
json = mapper.writeValueAsString(result.getRawValue());
System.out.println(json);
RawHello hello = mapper.readValue(json, RawHello.class);
System.out.println(hello.data);
RawHello.java
public class RawHello {
public String data;
}
RawJsonValue.java
public class RawJsonValue {
private Object rawValue;
public Object getRawValue() {
return rawValue;
}
public void setRawValue(Object value) {
this.rawValue = value;
}
}
I had a similar problem, but using a list with a lot of JSON itens (List<String>).
public class Errors {
private Integer status;
private List<String> jsons;
}
I managed the serialization using the #JsonRawValue annotation. But for deserialization I had to create a custom deserializer based on Roy's suggestion.
public class Errors {
private Integer status;
#JsonRawValue
#JsonDeserialize(using = JsonListPassThroughDeserialzier.class)
private List<String> jsons;
}
Below you can see my "List" deserializer.
public class JsonListPassThroughDeserializer extends JsonDeserializer<List<String>> {
#Override
public List<String> deserialize(JsonParser jp, DeserializationContext cxt) throws IOException, JsonProcessingException {
if (jp.getCurrentToken() == JsonToken.START_ARRAY) {
final List<String> list = new ArrayList<>();
while (jp.nextToken() != JsonToken.END_ARRAY) {
list.add(jp.getCodec().readTree(jp).toString());
}
return list;
}
throw cxt.instantiationException(List.class, "Expected Json list");
}
}

Categories

Resources