问题
I have a below JSON response that I am getting back from a rest service. Now I need to deserialize below JSON response into a POJO. I am working with Jackson.
{
"pagination": {
"number": 1,
"entriesPerPage": 200,
"total": 3
},
"postings": [{
"categories": [{
"taskid": "79720",
"name": "Sunglasses",
"parentCategory": {
"taskid": "394",
"name": "Sunglasses & Fashion Eyewear",
"parentCategory": {
"taskid": "2340",
"name": "Men's Accessories",
"parentCategory": {
"taskid": "10987",
"name": "Clothing, Shoes & Accessories"
}
}
}
}]
},
{
"categories": [{
"taskid": "12980",
"name": "Toys",
"parentCategory": {
"taskid": "123",
"name": "Fashion",
"parentCategory": {
"taskid": "78765",
"name": "Men's Accessories"
}
}
}]
}],
"total": 2
}
In above json, postings is a JSON array which can have multiple posting json object. Now categories is also JSON array. Now tricky part is I can have multiple levels of parentCategory inside each category object and I don't know how many levels of parentCategory I will have. Give above JSON, I need to extract taskid of each category and taskId of last parentCategory. So it should be like this:
79720=10987
12980=78765
Where 79720 is taskId of category and 10987 is the taskId of last parentCategory. Similarly for other one.
Below is my code where I am deserializing JSON into my POJO by making an http call:
ResponseEntity<Stuff> responseEntity = HttpClient.getInstance().getClient()
.exchange(URI.create(endpoint), HttpMethod.POST, requestEntity, Stuff.class);
Stuff response = responseEntity.getBody();
List<Posting> postings = response.getPostings();
for(Posting postings : postings) {
//....
}
Confusion I have is - How to make POJO for above JSON? I tried using jsonschema2pojo but it's not making right classes for parentCategory. Since I can have nested levels of parentCategory which I don't know before hand.
Is this possible to do using Jackson?
This is the POJO class generated for Category and ParentCategory. I am not sure whether I need to make any changes here so that I can parse recursive parentCategory object.
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({"taskid", "name", "parentCategory"})
public class Category {
@JsonProperty("taskid")
private String taskid;
@JsonProperty("name")
private String name;
@JsonProperty("parentCategory")
private ParentCategory parentCategory;
@JsonIgnore
private Map<String, Object> additionalProperties = new HashMap<String, Object>();
...
}
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({"taskid", "name", "parentCategory"})
public class ParentCategory {
@JsonProperty("taskid")
private String taskid;
@JsonProperty("name")
private String name;
@JsonProperty("parentCategory")
private ParentCategory parentCategory;
@JsonIgnore
private Map<String, Object> additionalProperties = new HashMap<String, Object>();
...
}
回答1:
This time I would approach with GSon
Which manages recursion with less effort.
Pojos can be made from json2pojo website, simply choosing GSon as JSon library.
These are the Pojos:
import java.io.Serializable;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Pagination implements Serializable
{
public Pagination() {
super();
// TODO Auto-generated constructor stub
}
@SerializedName("number")
@Expose
private Integer number;
@SerializedName("entriesPerPage")
@Expose
private Integer entriesPerPage;
@SerializedName("total")
@Expose
private Integer total;
private final static long serialVersionUID = 5114620434202813556L;
public Integer getNumber() {
return number;
}
public void setNumber(Integer number) {
this.number = number;
}
public Integer getEntriesPerPage() {
return entriesPerPage;
}
public void setEntriesPerPage(Integer entriesPerPage) {
this.entriesPerPage = entriesPerPage;
}
public Integer getTotal() {
return total;
}
public void setTotal(Integer total) {
this.total = total;
}
}
import java.io.Serializable;
import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Categories implements Serializable
{
public Categories() {
super();
// TODO Auto-generated constructor stub
}
@SerializedName("pagination")
@Expose
private Pagination pagination;
@SerializedName("postings")
@Expose
private List<Posting> postings = null;
@SerializedName("total")
@Expose
private Integer total;
private final static long serialVersionUID = 4589512697836725240L;
public Pagination getPagination() {
return pagination;
}
public void setPagination(Pagination pagination) {
this.pagination = pagination;
}
public List<Posting> getPostings() {
return postings;
}
public void setPostings(List<Posting> postings) {
this.postings = postings;
}
public Integer getTotal() {
return total;
}
public void setTotal(Integer total) {
this.total = total;
}
}
import java.io.Serializable;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Category implements Serializable
{
public Category() {
super();
// TODO Auto-generated constructor stub
}
@SerializedName("taskid")
@Expose
private String taskid;
@SerializedName("name")
@Expose
private String name;
@SerializedName("parentCategory")
@Expose
private ParentCategory parentCategory;
private final static long serialVersionUID = -2127963072268572959L;
public String getTaskid() {
return taskid;
}
public void setTaskid(String taskid) {
this.taskid = taskid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public ParentCategory getParentCategory() {
return parentCategory;
}
public void setParentCategory(ParentCategory parentCategory) {
this.parentCategory = parentCategory;
}
}
import java.io.Serializable;
import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Posting implements Serializable
{
@SerializedName("categories")
@Expose
private List<Category> categories = null;
private final static long serialVersionUID = 8135185675909461065L;
public List<Category> getCategories() {
return categories;
}
public Posting() {
super();
// TODO Auto-generated constructor stub
}
public void setCategories(List<Category> categories) {
this.categories = categories;
}
}
import java.io.Serializable;
import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class ParentCategory implements Serializable
{
@SerializedName("taskid")
@Expose
private String taskid;
@SerializedName("name")
@Expose
private String name;
@SerializedName("parentCategory")
@Expose
private List<ParentCategory> parentCategory;
public ParentCategory() {
super();
// TODO Auto-generated constructor stub
}
private final static long serialVersionUID = -5989749742502713615L;
public String getTaskid() {
return taskid;
}
public void setTaskid(String taskid) {
this.taskid = taskid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<ParentCategory> getParentCategory() {
return parentCategory;
}
public void setParentCategory(List<ParentCategory> parentCategory) {
this.parentCategory = parentCategory;
}
}
So this is a test implementation:
Pagination pagination = new Pagination();
pagination.setNumber(1);
pagination.setEntriesPerPage(200);
pagination.setTotal(3);
Categories categories = new Categories();
categories.setPagination(pagination);
Category category = new Category();
category.setName("Sunglasses");
category.setTaskid("79720");
List<Category> categoryList = new ArrayList<Category>();
Posting posting = new Posting();
posting.setCategories(categoryList);
List<ParentCategory> parentCategoryList = new ArrayList<ParentCategory>();
List<ParentCategory> parentCategoryList2 = new ArrayList<ParentCategory>();
ParentCategory parentCategory1 = new ParentCategory();
parentCategory1.setName("Sunglasses & Fashion Eyewear");
parentCategory1.setTaskid("394");
ParentCategory parentCategory2 = new ParentCategory();
parentCategory2.setName("Men's Accessories");
parentCategory2.setTaskid("2340");
ParentCategory parentCategory3 = new ParentCategory();
parentCategory3.setName("Clothing, Shoes & Accessories");
parentCategory3.setTaskid("10987");
parentCategoryList.add(parentCategory2);
parentCategoryList2.add(parentCategory3);
parentCategory2.setParentCategory(parentCategoryList2);
parentCategory1.setParentCategory(parentCategoryList);
category.setParentCategory(parentCategory1);
Gson gson = new Gson();
System.out.println(gson.toJson(category));
...and this is the resulting Json:
{
"taskid": "79720",
"name": "Sunglasses",
"parentCategory": {
"taskid": "394",
"name": "Sunglasses \u0026 Fashion Eyewear",
"parentCategory": [{
"taskid": "2340",
"name": "Men\u0027s Accessories",
"parentCategory": [{
"taskid": "10987",
"name": "Clothing, Shoes \u0026 Accessories"
}]
}]
}
}
Maybe still need a bit of tweaking but you got the idea.
Hope it helps!
EDIT: as the op requests I add the Jackson Version.
Pojos:
import java.io.Serializable;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({"taskid", "name", "parentCategory"})
public class ParentCategory implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
@JsonProperty("taskid")
private String taskid;
@JsonProperty("name")
private String name;
@JsonProperty("parentCategory")
private ParentCategory parentCategory;
public String getTaskid() {
return taskid;
}
public void setTaskid(String taskid) {
this.taskid = taskid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public ParentCategory getParentCategory() {
return parentCategory;
}
public void setParentCategory(ParentCategory parentCategory) {
this.parentCategory = parentCategory;
}
}
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({"taskid", "name", "parentCategory"})
public class Category implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
@JsonProperty("taskid")
private String taskid;
@JsonProperty("name")
private String name;
@JsonProperty("parentCategory")
private ParentCategory parentCategory;
public String getTaskid() {
return taskid;
}
public void setTaskid(String taskid) {
this.taskid = taskid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public ParentCategory getParentCategory() {
return parentCategory;
}
public void setParentCategory(ParentCategory parentCategory) {
this.parentCategory = parentCategory;
}
}
public class Test {
public static void main(String[] args) throws JsonProcessingException {
Category category = new Category();
category.setName("Sunglasses");
category.setTaskid("79720");
List<Category> categoryList = new ArrayList<Category>();
List<ParentCategory> parentCategoryList = new ArrayList<ParentCategory>();
List<ParentCategory> parentCategoryList2 = new ArrayList<ParentCategory>();
ParentCategory parentCategory1 = new ParentCategory();
parentCategory1.setName("Sunglasses & Fashion Eyewear");
parentCategory1.setTaskid("394");
ParentCategory parentCategory2 = new ParentCategory();
parentCategory2.setName("Men's Accessories");
parentCategory2.setTaskid("2340");
ParentCategory parentCategory3 = new ParentCategory();
parentCategory3.setName("Clothing, Shoes & Accessories");
parentCategory3.setTaskid("10987");
parentCategory1.setParentCategory(parentCategory2);
parentCategory2.setParentCategory(parentCategory3);
category.setParentCategory(parentCategory1);
ObjectMapper objectMapper = new ObjectMapper();
String testJson = objectMapper.writeValueAsString(category);
System.out.println(testJson);
}
}
And here again a test result:
{
"taskid": "79720",
"name": "Sunglasses",
"parentCategory": {
"taskid": "394",
"name": "Sunglasses & Fashion Eyewear",
"parentCategory": {
"taskid": "2340",
"name": "Men's Accessories",
"parentCategory": {
"taskid": "10987",
"name": "Clothing, Shoes & Accessories"
}
}
}
}
来源：https://stackoverflow.com/questions/48469722/how-to-make-pojo-and-parse-recursive-objects-using-jackson