(Deserializing) Complex JSON to Java objet(List) with Jackson

Question

I am completely new in Json und I am trying to deserialize a complex Json with complex types (all these Elements are Classes from my programm: entete, pied-depage, corps (List<classe like garantie,..>), nomain, labels, lieu, garantie , Elt). I try to deserialize this Json to a List from type class Tester. ``json

[{
“ entete“:{
    "titre" :,  "Nummer" : , 
    … }
“ pied-depage“:{
    "utilisateur" : "martin"
    … }
“ Corps“:[{
 "reservation" : 0.00,
    
    "garantie" : [ ],
    "Utilisateurs" : [ ],

           …}
…}]
“ nomain“: $
“ daterRange“: {}
“ labels“:{}
"date1" : "1988-01-01",
"date2" : "1528-12-31"
}]
``` 

```java Code

Class Tester{

private  entete header =  entete.getHeader();
private pied-depage footer = pied-depage.getFooter(); 
private List<Elt> Corps;
private Elt anlagengut;
private String nomain;
private LocalDateRange dateRange;

public LocalDate getDate1() {
  return this.dateRange.getStart();
}

public LocalDate getDate2() {
  return this.dateRange.getEndInclusive();
}

getter ...

}


public static List<Tester> getCollection()  throws IOException
{

ObjectMapper mapper = new ObjectMapper();

mapper.registerModules( new JavaTimeModule());
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false)
    .findAndRegisterModules();

List<Tester>  tester = (List<Tester>) mapper.readValue(Paths.get("Tester.json").toFile(), List.class);
return tester;
}
```

I am trying after serialization of the same Object with Jackson to deserialize the produced Json to have the identic container in another program. do you have any indication for me? I have already written these but I get an object with elements of Type LinkedHashMap

Answer 1

[{
“ entete“:{
    "titre" :,  "Nummer" : , 
    … }
“ pied-depage“:{
    "utilisateur" : "martin"
    … }
“ Corps“:[{
 "reservation" : 0.00,
    
    "garantie" : [ ],
    "Utilisateurs" : [ ],

           …}
…}]
“ nomain“: $
“ daterRange“: {}
“ labels“:{}
"date1" : "1988-01-01",
"date2" : "1528-12-31"
}]
``` 

Kindly see reference below:

When you see { } , You can either create a Class to map the properties, or you can use Map<String, String>

When you see [{}] , You can use a List<YourCustomClass> or List<Map<String, String>>

Use @JsonProperty("YourWeirdPropertyNameHere") if you want to map your Class Properties towards JSON Properties which have different cases/names

When mapping properties,

entete“:{
    "titre" :,  "Nummer" : , 
    … }

Then a class representation will look like:

public class Entete {

 private String titre;     //String because the value is "Number" which is in ""

}

For

“ Corps“:[{
     "reservation" : 0.00,
        
        "garantie" : [ ],
        "Utilisateurs" : [ ],
    
               …}
    …}]

Then a class representation will look like:

public class Corp{
   
  private Double reservation;
  private List<String> garantie;

  @JsonProperty("Utilisateurs")
  private List<String> utilisateurs;

}

Then you can create the mapper class Test:

public class Test{

  public Entete entete;

  @JsonProperty("pied-depage")
  public PiedDepage piedDepage;

  @JsonProperty("Corps")
  public List<Corp> corps;
 
   
}

And to use ObjectMapper, you need to pass TypeReference:

List<Test> myTests = mapper.readValue(jsonInput, new TypeReference<List<Test>>(){});