如何使用 jackson 制作 POJO 和解析递归对象？
How to make POJO and parse recursive objects using jackson?
我有一个低于 JSON 的回复，我正在从休息服务中回来。现在我需要将下面的 JSON 响应反序列化为 POJO。我在和杰克逊一起工作。
{
"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
}
在上面json中，postings是一个JSON数组，可以有多个posting json对象。现在 categories 也是 JSON 数组。现在棘手的部分是我可以在每个类别对象中有多个 parentCategory 级别，但我不知道我将拥有多少个 parentCategory 级别。给上面JSON，我需要提取每个类别的taskid和最后parentCategory的taskId。所以应该是这样的：
79720=10987
12980=78765
其中79720是类别的taskId，10987是最后一个parentCategory的taskId。另一个也是如此。
下面是我的代码，我通过 http 调用将 JSON 反序列化到我的 POJO 中：
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) {
//....
}
我的困惑是 - 如何为以上 JSON 制作 POJO？我尝试使用 jsonschema2pojo，但它没有为 parentCategory 生成正确的 classes。因为我可以有嵌套级别的 parentCategory，我事先不知道。
使用 Jackson 可以做到这一点吗？
这是为 Category 和 ParentCategory 生成的 POJO class。我不确定我是否需要在这里进行任何更改以便我可以解析递归 parentCategory 对象。
@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>();
...
}
这次我会GSon
管理递归更省力。
Pojos 可以从 json2pojo 网站制作，只需选择 GSon 作为 JSon 库。
这些是 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;
}
}
所以这是一个测试实现：
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));
...这就是结果 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"
}]
}]
}
}
也许还需要一些调整，但您明白了。
希望对您有所帮助！
编辑：根据操作要求，我添加了 Jackson 版本。
波霍斯：
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);
}
}
这里又是一个测试结果：
{
"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"
}
}
}
}
我有一个低于 JSON 的回复，我正在从休息服务中回来。现在我需要将下面的 JSON 响应反序列化为 POJO。我在和杰克逊一起工作。
{
"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
}
在上面json中，postings是一个JSON数组，可以有多个posting json对象。现在 categories 也是 JSON 数组。现在棘手的部分是我可以在每个类别对象中有多个 parentCategory 级别，但我不知道我将拥有多少个 parentCategory 级别。给上面JSON，我需要提取每个类别的taskid和最后parentCategory的taskId。所以应该是这样的：
79720=10987
12980=78765
其中79720是类别的taskId，10987是最后一个parentCategory的taskId。另一个也是如此。
下面是我的代码，我通过 http 调用将 JSON 反序列化到我的 POJO 中：
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) {
//....
}
我的困惑是 - 如何为以上 JSON 制作 POJO？我尝试使用 jsonschema2pojo，但它没有为 parentCategory 生成正确的 classes。因为我可以有嵌套级别的 parentCategory，我事先不知道。
使用 Jackson 可以做到这一点吗？
这是为 Category 和 ParentCategory 生成的 POJO class。我不确定我是否需要在这里进行任何更改以便我可以解析递归 parentCategory 对象。
@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>();
...
}
这次我会GSon
管理递归更省力。
Pojos 可以从 json2pojo 网站制作，只需选择 GSon 作为 JSon 库。
这些是 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;
}
}
所以这是一个测试实现：
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));
...这就是结果 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"
}]
}]
}
}
也许还需要一些调整，但您明白了。
希望对您有所帮助！
编辑：根据操作要求，我添加了 Jackson 版本。
波霍斯：
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);
}
}
这里又是一个测试结果：
{
"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"
}
}
}
}