Java 向视图发送数据时获取JsonMappingException
我正在尝试向我的网页显示DB数据。 当GET请求到Java 向视图发送数据时获取JsonMappingException,java,ajax,json,spring-mvc,jackson,Java,Ajax,Json,Spring Mvc,Jackson,我正在尝试向我的网页显示DB数据。 当GET请求到@RequestMapping(value=“/api/binder”)时,我生成了以下代码 但当get请求到达这个方法时,它将获取数据(我在控制台上打印并显示得很好),但它没有映射到我的Java脚本Ajax调用,它向我显示了一个错误 以下是我获取数据的代码: @Autowired IBinderViewRepository repository; @RequestMapping(method= RequestMetho
@RequestMapping(value=“/api/binder”)
时,我生成了以下代码
但当get请求到达这个方法时,它将获取数据(我在控制台上打印并显示得很好),但它没有映射到我的Java脚本Ajax调用,它向我显示了一个错误
以下是我获取数据的代码:
@Autowired
IBinderViewRepository repository;
@RequestMapping(method= RequestMethod.GET)
public @ResponseBody
List<BinderResponse> getBinders(){
List<BinderView> binders = repository.getBinders();
List<BinderResponse> responses = new ArrayList<>();
ModelMapper mapper = Mapper.getInstance();
for(int i = 0; i < binders.size(); i++){
System.out.println("In Loop");
BinderResponse response = mapper.map(binders.get(i),BinderResponse.class);
System.out.println("Data :: " + response.getBinderName());
responses.add(response);
}
return responses;
}
下面是来自knockout js的ajax调用:
ajax.get('api/binder').done(函数(响应){…}
此处BinderView和BinderResponse具有相同的字段:
private String binderName;
private String binderAddress1;
和盖特·塞特在这两个方面都是如此。
和repository.genBinders()
方法从数据库中获取数据
以下是insert方法,对我来说效果很好:
@RequestMapping(method= RequestMethod.POST,consumes = "application/json")
public @ResponseBody
IWebApiResponse addBinder(@RequestBody AddBinderForm binder){
.....
}
我需要在BinderResponse类上添加任何json注释吗?
我不明白我错在哪里?有人请引导我
更新:
BinderView:
public class BinderView extends BaseView {
private String binderName;
private String binderAddress1;
public String getBinderName() {
return binderName;
}
public void setBinderName(String binderName) {
this.binderName = binderName;
}
public String getBinderAddress1() {
return binderAddress1;
}
public void setBinderAddress1(String binderAddress1) {
this.binderAddress1 = binderAddress1;
}
}
在控制台中,它打印数据/BinderName:
In Loop
Data :: ada
In Loop
Data :: tya
新更新:
下面是BaseView的:
@MappedSuperclass
public abstract class BaseView implements IEntity {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue
@Column(name="id")
private long id;
public long getId() {
return id;
}
public void setId(long id) {
if (this.id != 0 && this.id != id) {
throw new IllegalStateException(
"The ID must not be changed after it is set.");
}
this.id = id;
}
}
public interface IEntity extends Serializable {
long getId();
void setId(long id);
}
public class WebApiResponseBase implements IWebApiResponse {
private String _uri;
@Override
public String getUri() {
return _uri == null ? "" : _uri;
}
@Override
public void setUri(String uri) {
_uri = uri;
}
}
而在中:
@MappedSuperclass
public abstract class BaseView implements IEntity {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue
@Column(name="id")
private long id;
public long getId() {
return id;
}
public void setId(long id) {
if (this.id != 0 && this.id != id) {
throw new IllegalStateException(
"The ID must not be changed after it is set.");
}
this.id = id;
}
}
public interface IEntity extends Serializable {
long getId();
void setId(long id);
}
public class WebApiResponseBase implements IWebApiResponse {
private String _uri;
@Override
public String getUri() {
return _uri == null ? "" : _uri;
}
@Override
public void setUri(String uri) {
_uri = uri;
}
}
WebApiResponseBase:
@MappedSuperclass
public abstract class BaseView implements IEntity {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue
@Column(name="id")
private long id;
public long getId() {
return id;
}
public void setId(long id) {
if (this.id != 0 && this.id != id) {
throw new IllegalStateException(
"The ID must not be changed after it is set.");
}
this.id = id;
}
}
public interface IEntity extends Serializable {
long getId();
void setId(long id);
}
public class WebApiResponseBase implements IWebApiResponse {
private String _uri;
@Override
public String getUri() {
return _uri == null ? "" : _uri;
}
@Override
public void setUri(String uri) {
_uri = uri;
}
}
默认情况下,Jackson序列化对象的整个继承层次结构,即父类字段
public class BinderResponse extends WebApiResponseBase {
好像
Could not write JSON: (was java.lang.NullPointerException) (through reference chain: java.util.ArrayList[0]->com.ngl.dto.outgoing.BinderResponse["valid"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: java.util.ArrayList[0]->com.ngl.dto.outgoing.BinderResponse["valid"])
Jackson试图从名为isValid
(这是一个传统的bean属性名称)的getter中序列化名为valid
的字段。然而,getter方法似乎出于任何原因抛出了NullPointerException
如果希望Jackson忽略它,可以使用@JsonIgnore
注释getter,或者使用@JsonIgnoreProperties
注释类,并指定属性名,即有效
@Column(name="createddate")
private Date createdDate;
@Transient
private String formatedCreatedDate;
public String getFormatedCreatedDate() {
DateFormat dateFormat = new SimpleDateFormat("dd/mm/yyyy");
return dateFormat.format(this.getCreatedDate());
}
它会引发相同的异常,因为通过调用getCreatedDate()value come,此处可能为null,因此无法格式化null date,因此请在此处保持null检查,如:
解决方案
public String getFormatedCreatedDate() {
DateFormat dateFormat = new SimpleDateFormat("dd/mm/yyyy");
Date createDdate=this.getCreatedDate();
**if(createDdate!=null){
return dateFormat.format(createDdate);
}**
return "-";
}
在我的例子中,当我使用@JsonIgnore
时,异常已经消失,但问题是它无法再从API请求
接收该值,Spring忽略了它(显然是因为@JsonIgnore
)所以我调查了这个问题,发现问题出在getter
和setter
。
我有Integer
属性,而我的getter
是int
。因此,当我将getter
更改为Integer
时,我的问题解决了,错误消失了
private Integer purchaseId;
@JsonIgnore
public int getPurchaseId() {
return purchaseId;
}
public void setPurchaseId(int purchaseId) {
this.purchaseId = purchaseId;
}
改为:
private Integer purchaseId;
public Integer getPurchaseId() {
return purchaseId;
}
public void setPurchaseId(Integer purchaseId) {
this.purchaseId = purchaseId;
}
看看您的响应包含什么内容。您似乎有一个名为valid
的BinderResponse
字段,即null
。该字段是什么?您在webapirresponsebase中有一个NullPointerException
。是否有效
。您对此进行过调查吗?是的,除此之外,它还是有效的bean属性名,因此Jackson将尝试为其创建一个JSON字段。这似乎是导致NPE的原因。查看@JsonIgnoreProperties
注释。我的变量定义为“Double”,getter和setter为“Double”。将变量从“Double”更改为“Double”对我来说很有效。