Develop Reference

Using #JsonIdentityInfo along with #JsonSerialize with a custom converter

I am trying to serialise an object by converting it first to another object. At the same time I do not want to serialise twice the same object so I am using #JsonIdentityReference to serialise it only the first time. However since the converter will always create a new output object for the same input object the entire object is serialised every time. Is there a way to avoid serialising twice the same object while at the same time using a converter?
The Domain class
#JsonSerialize(converter = BooleanWithNameConverter.class)
#JsonDeserialize(converter = BooleanWithNameDtoConverter.class)
public class BooleanWithName {
private final boolean value;
private final String name;
BooleanWithName(String name, boolean value) {
this.name = name;
this.value = value;
}
public String getName() {
return name;
}
public boolean getValue() {
return value;
}
}
The DTO
#JsonIdentityInfo(generator = ObjectIdGenerators.UUIDGenerator.class)
public class BooleanWithNameDto {
private final boolean value;
private final String name;
#JsonCreator
BooleanWithNameDto(#JsonProperty("name") String name, #JsonProperty("value") boolean value) {
this.name = name;
this.value = value;
}
public String getName() {
return name;
}
public boolean getValue() {
return value;
}
}
The converter to the DTO
public class BooleanWithNameConverter extends StdConverter<BooleanWithName, BooleanWithNameDto> {
#Override
public BooleanWithNameDto convert(BooleanWithName obj) {
return new BooleanWithNameDto(obj.getName(), obj.getValue());
}
}
The converter back to the domain object
This is not strictly needed since the problem can be seen just by examining the json string but helpful in order to add a small unit test demonstrating the problem
public class BooleanWithNameDtoConverter extends StdConverter<BooleanWithNameDto, BooleanWithName> {
#Override
public BooleanWithName convert(BooleanWithNameDto obj) {
return new BooleanWithName(obj.getName(), obj.getValue());
}
}
A small unit test that fails
public class UnitTest {
#Test
public void testConverter() throws JsonProcessingException {
BooleanWithName booleanWithName = new BooleanWithName("dummy", true);
ObjectMapper objectMapper = new ObjectMapper();
BooleanWithName[] value = { booleanWithName, booleanWithName };
BooleanWithName[] readValue = objectMapper.readValue(objectMapper.writeValueAsString(value), BooleanWithName[].class);
Assertions.assertEquals(readValue[0], readValue[1]);
}
}
Thanks a lot!

JSON serialize to a different value

I have the below json which im serializing
{
"name":"John",
"switch":"1"
},
{
"name":"Jim",
"switch":"0"
}
I want to serialize it to a differnt name So I had to do it like below
class Data {
private String name;
private String flag;
#JsonProperty("flag")
public byte getFlag() {
return flag;
}
#JsonProperty("switch")
public void setSwitch(String s) {
this.flag = flag;
}
}
So that I get it converted as below
{
"name":"John",
"flag":"1"
},
{
"name":"Jim",
"flag":"0"
}
Now I wanted to map the numic values to Y and N for 1 and 0 respectively. Can I acheive that ?
Im expecting my final string to be like this
{
"name":"John",
"switch":"Y"
},
{
"name":"Jim",
"switch":"N"
}

I agree with #Gaël J, but still if you want to go ahead this code change might help you to convert that 1/0 to Y/N.
public class Application {
#ToString
static class Input {
#JsonProperty("name")
private String name;
#JsonProperty("switch")
private String flag;
#JsonProperty("name")
public void setName(String name){
this.name = name;
}
#JsonProperty("switch")
public void setSwitch(String s) {
for(SwitchMap valuePair : SwitchMap.values()){
if(valuePair.getValue().equals(s)){
this.flag = valuePair.name();
}
}
}
}
public static void main(String[] args) throws JsonProcessingException {
String json = "{\n" +
"\"name\":\"John\",\n" +
"\"switch\":\"1\"\n" +
"}";
ObjectMapper mapper = new ObjectMapper();
Input in = mapper.readValue(json, Input.class);
System.out.println(mapper.writeValueAsString(in));
}
}
define an enum with the mapping
#Getter
public enum SwitchMap {
Y("1"),
N("0");
private final String value;
private SwitchMap(String value){
this.value = value;
}
}

Convert dynamic json to java object with dynamic string value. No key value json structure

I want to convert below JSON structure to java object, Annotation bases.
What will be the pojo java class structure?
{
"Data1":{
"Name":"abc",
"Number":2
}
}
Data1 can by any string-like if it coming as data1 first time, next time it can be like "xyz".
How can we convert it using fasterxml json annotations?

class Node {
public String name;
public int number
}
class ConvertedPojo {
public Map<String, Node> attributes;
}
Since Data1 can be any string you need a map which will store all different string as key and value as json object

Class structure will be :
public class Data1{
#JsonProperty("Name")
private String name;
#JsonProperty("Number")
private int number;
public String getName() {
return name;
}
public void setName(String name) {
name = name;
}
public int getNumber() {
return number;
}
public void setNumber(int number) {
number = number;
}
}
public class Data {
#JsonProperty("Data1")
Object data1;
public Object getData1() {
return data1;
}
public void setData1(Object data1) {
this.data1 = data1;
}
}
Take care of the variable naming convention.
Code to test:
public static void main(String[] args) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
Data data1 = mapper.readValue("{\"Data1\":{\"Name\":\"abc\",\"Number\":2}}", Data.class);
System.out.println(mapper.writeValueAsString(data1));//{"Data1":{"Name":"abc","Number":2}}
Data data2 = mapper.readValue("{\"Data1\":\"data value\"}", Data.class);
System.out.println(mapper.writeValueAsString(data2));//{"Data1":"data value"}
}

Handle different types for some fields while serializing and deserializing with Jackson

I am using Jackson 2.
When reading from remote service I obtain a JSON object like this:
{
"country":"1",
"complex":{
"link":"...",
"value":"..."
},
"test":""
}
so I have created the related POJOs for the purpose:
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({
"link",
"value"
})
public class Complex {
#JsonProperty("link")
private String link;
#JsonProperty("value")
private String value;
#JsonProperty("link")
public String getLink() {
return link;
}
#JsonProperty("link")
public void setLink(String link) {
this.link = link;
}
#JsonProperty("value")
public String getValue() {
return value;
}
#JsonProperty("value")
public void setValue(String value) {
this.value = value;
}
}
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({
"country",
"complex",
"test"
})
public class Resource {
#JsonProperty("country")
private String country;
#JsonProperty("complex")
private Complex complex;
#JsonProperty("test")
private String test;
#JsonProperty("country")
public String getCountry() {
return country;
}
#JsonProperty("country")
public void setCountry(String country) {
this.country = country;
}
#JsonProperty("complex")
public Complex getComplex() {
return complex;
}
#JsonProperty("complex")
public void setComplex(Complex complex) {
this.complex = complex;
}
#JsonProperty("test")
public String getTest() {
return test;
}
#JsonProperty("test")
public void setTest(String test) {
this.test = test;
}
}
so that I'm able to do:
Resource res = MAPPER.readValue(response.readEntity(String.class), Resource.class);
My problem is that, when executing POST requests, I need to send a different object, that is:
{
"country":"1",
"complex": "value",
"test":""
}
so where all "complex" objects must be simply strings.
Any idea about how to handle this situation?
I have tried to create a JsonDeserializer class:
public class ComplexValueDeserializer extends JsonDeserializer<Object> {
#Override
public Object deserialize(final JsonParser parser, final DeserializationContext deserializationContext)
throws IOException, JsonProcessingException {
final JsonToken jsonToken = parser.getCurrentToken();
if (jsonToken == null
|| (jsonToken == JsonToken.START_OBJECT && parser.getValueAsString().equals("{}"))) {
return "";
}
return null;
}
}
and add it to:
#JsonProperty("complex")
#JsonDeserialize(using = ComplexValueDeserializer.class)
private Complex complex;
but I get java.lang.IllegalArgumentException: argument type mismatch error.
Thanks!

On your Complex Object type you can define a toString() method and then Annotate it with #JsonValue. This will indicate to Jackson that the returned result will be the value serialized for that object. You can them implement whatever logic you need there to represent the Complex type in the way you want. e.g.:
#JsonValue
public String toString() {
return value;
}

Why do you need
"complex":{
"link":"...",
"value":"..."
},
for api documentation?

spring data cassandra saving only a single object in the list

Model
#Table(value = "bad_data")
public class BadData {
private String objectID;
private String type;
private String problems;
private String owner;
private String formattedID;
private String project;
#PrimaryKey
private String train;
private String status;
/* Default constructor. */
public BadData () {
this.objectID = "";
this.type = "";
this.problems = "";
this.owner = "";
this.formattedID = "";
this.project = "";
this.train = "";
this.status = "";
}
/* Getters and setters. */
public void setObjectID (String objectID) {
this.objectID = objectID;
}
public String getObjectID () {
return this.objectID;
}
public void setType (String type) {
this.type = type;
}
public String getType () {
return this.type;
}
public void setProblems (String problems) {
this.problems = problems;
}
public String getProblems () {
return this.problems;
}
public void setOwner (String owner) {
this.owner = owner;
}
public String getOwner () {
return this.owner;
}
public void setFormattedID (String formattedID) {
this.formattedID = formattedID;
}
public String getFormattedID () {
return this.formattedID;
}
public void setProject (String project) {
this.project = project;
}
public String getProject () {
return this.project;
}
public void setTrain (String train) {
this.train = train;
}
public String getTrain () {
return this.train;
}
public void setStatus (String status) {
this.status = status;
}
public String getStatus () {
return this.status;
}
}
Repository
#Autowired
public void save (CassandraOperations db) {
BadData badData1 = new BadData();
badData1.setTrain("train");
badData1.setFormattedID("fid");
badData1.addProblems("problem1");
badData1.setObjectID("id");
badData1.setOwner("lokesh");
badData1.setType("story");
badData1.setProject("om");
badData1.setStatus("open");
BadData badData2 = new BadData();
badData2.setTrain("train");
badData2.setFormattedID("fid");
badData2.addProblems("problem2");
badData2.setObjectID("id");
badData2.setOwner("lokesh");
badData2.setType("story");
badData2.setProject("om");
badData2.setStatus("open");
BadData badData3 = new BadData();
badData3.setTrain("train");
badData3.setFormattedID("fid");
badData3.addProblems("problem3");
badData3.setObjectID("id");
badData3.setOwner("lokesh");
badData3.setType("story");
badData3.setProject("om");
badData3.setStatus("open");
List<BadData> data = new ArrayList<>();
data.add(badData1);
data.add(badData3);
data.add(badData2);
db.insert(data);
}
I am trying to save three objects placing them in list. I got only one object (badData3) saved into the database. I changed the order of those objects in the list. i noticed that which ever object is in the middle of the list is getting saved. Can some one guess what could be the possible error be

Yes (krsyk is correct), the value ("train") of your #PrimaryKey field (train) is the same for all entities in your List.
Also, you should have a look at the corresponding test case (insertBatchTest) in test class (CassandraDataOperationsTest) in the SD Cassandra test suite.
For reassurance, I added the following code snippet to the end of the test...
assertThat(template.count(Book.class), is(equalTo(80l)));
And, the test passed as expected.
Note, I was using the latest Spring Data Cassandra 1.4.2.RELEASE.
Also note, because every INSERT or UPDATE in Cassandra is actually an "UPSERT" (see here), then you are effectively overwriting each entry (entity) in your List because of the duplicate primary key value.

Your #PrimaryKey is train field, and you set this field in each object to the same value: "train" so they will override each other.