请求处理失败；嵌套异常是 java.lang.IllegalStateException：

Question

Product.java --

package com.niit.model;


import javax.persistence.Column;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;


@Entity
public class Product {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO) //Automatically generate value for Id using sequence
private int id;
private String productname;
private String productDescription;
private int quantity;
private double price;
@ManyToOne
private Category category;
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getProductname() {
    return productname;
}
public void setProductname(String productname) {
    this.productname = productname;
}
public int getQuantity() {
    return quantity;
}
public void setQuantity(int quantity) {
    this.quantity = quantity;
}
public double getPrice() {
    return price;
}
public void setPrice(double price) {
    this.price = price;
}
public String getProductDescription() {
    return productDescription;
}
public void setProductDescription(String productDescription) {
    this.productDescription = productDescription;
}

Category.java--

package com.niit.model;

import java.util.List;


import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entity
public class Category {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
private int id;
private String categoryname;
@OneToMany(mappedBy="category")
private List<Product> products;
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getCategoryname() {
    return categoryname;
}
public void setCategoryname(String categoryname) {
    this.categoryname = categoryname;
}
}

遇到内部错误 500：

HTTP 状态 500 – 内部服务器错误

键入异常报告

消息请求处理失败；嵌套异常是 java.lang.IllegalStateException：存在可选的 int 参数“id”，但由于被声明为原始类型，因此无法转换为空值。考虑将其声明为相应原始类型的对象包装器。

描述服务器遇到了一个意外情况，导致它无法完成请求。

例外

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException: Optional int parameter 'id' is present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

java.lang.IllegalStateException: Optional int parameter 'id' is present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.
    org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.handleNullValue(AbstractNamedValueMethodArgumentResolver.java:238)
    org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:111)
    org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
    org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Answer 1

这个错误几乎是不言自明的：你不能将原语声明为空， 例如：私有 int id = null;不会编译。所以不要使用 int 使用 Integer ，你应该很高兴。