JSONMappingException - 无法对Java对象进行desierialize [英] JSONMappingException - cannot desierialize Java object
问题描述
使用 ObjectMapper
对对象进行反序列化时出现以下错误:
I'm getting the following error when using an ObjectMapper
to de-serialize an object:
JSONMappingException无法构造
org.springframework.data.Page的实例,问题:抽象类型只能用
实例化其他类型信息。
JSONMappingException Can not construct instance of org.springframework.data.Page, problem: abstract types can only be instantiated with additional type information.
我正在尝试将JSON字符串序列化为Spring数据对象 org.springframework.data.Page
代表一个页面类型 T
。
I am trying to serialize a JSON string into a Spring data object org.springframework.data.Page
which represents a page of type T
.
用户
类是一个简单的POJO,第一个
和最后一个
名称。我反序列化的JSON字符串是:
The User
class is a simple POJO with first
and last
name. The JSON string I am deserializing is:
{
"content": [
{
"firstname": "John",
"lastname": "Doe"
},
{
"firstname": "Jane",
"lastname": "Doe"
}
],
"size": 2,
"number": 0,
"sort": [
{
"direction": "DESC",
"property": "timestamp",
"ascending": false
}
],
"totalPages": 150,
"numberOfElements": 100,
"totalElements": 15000,
"firstPage": true,
"lastPage": false
}
这会导致异常:
Page<User> userPage = (Page<User>) new ObjectMapper().mapToJavaObject(json, new TypeReference<Page<User>>(){};
由于 Page
是一个Spring对象,我无法修改它,我认为这与我在别处看到这个问题的方式有点不同有什么想法吗?
Since Page
is a Spring object I cannot modify it which I think makes this a bit different from the way I see this question asked elsewhere. Any thoughts?
推荐答案
我最终使用了这样的东西,创建了一个像@Perception建议的bean:
I ended up using something like this, creating a bean as @Perception suggested:
import java.util.ArrayList;
import java.util.List;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
public class PageImplBean<T> extends PageImpl<T> {
private static final long serialVersionUID = 1L;
private int number;
private int size;
private int totalPages;
private int numberOfElements;
private long totalElements;
private boolean previousPage;
private boolean firstPage;
private boolean nextPage;
private boolean lastPage;
private List<T> content;
private Sort sort;
public PageImplBean() {
super(new ArrayList<T>());
}
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
public int getTotalPages() {
return totalPages;
}
public void setTotalPages(int totalPages) {
this.totalPages = totalPages;
}
public int getNumberOfElements() {
return numberOfElements;
}
public void setNumberOfElements(int numberOfElements) {
this.numberOfElements = numberOfElements;
}
public long getTotalElements() {
return totalElements;
}
public void setTotalElements(long totalElements) {
this.totalElements = totalElements;
}
public boolean isPreviousPage() {
return previousPage;
}
public void setPreviousPage(boolean previousPage) {
this.previousPage = previousPage;
}
public boolean isFirstPage() {
return firstPage;
}
public void setFirstPage(boolean firstPage) {
this.firstPage = firstPage;
}
public boolean isNextPage() {
return nextPage;
}
public void setNextPage(boolean nextPage) {
this.nextPage = nextPage;
}
public boolean isLastPage() {
return lastPage;
}
public void setLastPage(boolean lastPage) {
this.lastPage = lastPage;
}
public List<T> getContent() {
return content;
}
public void setContent(List<T> content) {
this.content = content;
}
public Sort getSort() {
return sort;
}
public void setSort(Sort sort) {
this.sort = sort;
}
public PageImpl<T> pageImpl() {
return new PageImpl<T>(getContent(), new PageRequest(getNumber(),
getSize(), getSort()), getTotalElements());
}
}
然后修改你的代码以使用具体的类和获取PageImpl:
and then modify your code to use the concrete class and get the PageImpl:
@SuppressWarnings("unchecked")
Page<User> userPage = ((PageImplBean<User>)new ObjectMapper().readValue(json, new TypeReference<PageImplBean<User>>() {})).pageImpl();
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