字段需要一个无法找到的类型的 bean

Question

I am a spring boot learner so that I have been trying to create some basics Spring boot application. I got an error while I tried to run my developed application.

The error I got was [![ https://i.stack.imgur.com/oyQDi.png][1]][1]

StoreApiAPP.java:

package io.ajithan.springbootstarter;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan({"io.ajithan.springbootstarter"})
public class StoreApiAPP {

    public static void main(String[] args) {
        SpringApplication.run(StoreApiAPP.class, args);

    }

}

ItemDetails.java: [package name : io.ajithan.springbootstarter.model]

package io.ajithan.springbootstarter.model;


public class ItemDetails {
    private Integer itemId;
    private String itemName;
    private Double itemPrice;
    private String itemCategory;

    public ItemDetails() {

    }

    public ItemDetails(Integer itemId, String itemName, Double itemPrice, String itemCategory) {
        this.itemId = itemId;
        this.itemName = itemName;
        this.itemPrice = itemPrice;
        this.itemCategory = itemCategory;
    }


    public Integer getItemId() {
        return itemId;
    }
    public void setItemId(Integer itemId) {
        this.itemId = itemId;
    }
    public String getItemName() {
        return itemName;
    }
    public void setItemName(String itemName) {
        this.itemName = itemName;
    }
    public Double getItemPrice() {
        return itemPrice;
    }
    public void setItemPrice(Double itemPrice) {
        this.itemPrice = itemPrice;
    }
    public String getItemCategory() {
        return itemCategory;
    }
    public void setItemCategory(String itemCategory) {
        this.itemCategory = itemCategory;
    }

}

ItemResponse.java:[package name : io.ajithan.springbootstarter.model]

package io.ajithan.springbootstarter.model;

public class ItemResponse {
public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

private String message;
}

StoreController.java:[package name : io.ajithan.springbootstarter.controller]

package io.ajithan.springbootstarter.controller;


import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import io.ajithan.springbootstarter.model.ItemDetails;
import io.ajithan.springbootstarter.model.ItemResponse;
import io.ajithan.springbootstarter.service.StoreService;

@RestController
public class StoreController {
    @Autowired
    private StoreService storeService; 

    @RequestMapping("/getAllItems")
    public List<ItemDetails> getItemDetailsList(){
        return storeService.getItemDetails();
    }

    @RequestMapping("/getSingleItem/{idNumber}")
    public ItemDetails getSingleItem(@PathVariable("idNumber") Integer id) {
        return storeService.getSingleItem(id);
    }

    @RequestMapping(method=RequestMethod.POST,value="/addItem")
    public ItemResponse addSingleItem(@RequestBody ItemDetails itemDetails) {
        return storeService.addSingleItem(itemDetails);
    }


}

StoreService.java:[package name : io.ajithan.springbootstarter.service]

package io.ajithan.springbootstarter.service;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import io.ajithan.springbootstarter.model.ItemDetails;
import io.ajithan.springbootstarter.model.ItemResponse;

@Service
public class StoreService {

    @Autowired
    private ItemResponse itemResponse;

    private List<ItemDetails> itemDetailsList = new ArrayList<>(Arrays.asList(
            new ItemDetails(1,"5Rs GOODDAY Biscuit",5.00,"SWEET"),
            new ItemDetails(2,"10Rs GOODAY Biscuit,",10.00,"SALTY"),
            new ItemDetails(3,"25Rs GOODAY Biscuit",25.00,"CREAMY")
            ));
    public List<ItemDetails> getItemDetails()
    {
        return itemDetailsList;
    }
    public ItemDetails getSingleItem(Integer id) {
        return itemDetailsList.stream().filter(n->n.getItemId().equals(id)).findFirst().get();
    }

    public ItemResponse addSingleItem(ItemDetails itemDetails) {
        itemDetailsList.add(itemDetails);
        itemResponse.setMessage("Item added successfully");
        return itemResponse;
    }

}

Can anyone give me solution for this problem?

Answer 1

It doesn't make any sense and is actual dangerous in this case, to autowire the ItemResponse .

By default beans in Spring are singletons, so there is now a single instance of the ItemResponse . Now imagine 50 concurrent threads changing the single instance of ItemResponse , what output do you think each thread will have?

In your case the only proper solution is to remove the autowired field, and simply construct a new ItemResponse inside the addSingleItem method and return that. That way there is no shared state.

@Service
public class StoreService {

    private List<ItemDetails> itemDetailsList = new ArrayList<>(Arrays.asList(
            new ItemDetails(1,"5Rs GOODDAY Biscuit",5.00,"SWEET"),
            new ItemDetails(2,"10Rs GOODAY Biscuit,",10.00,"SALTY"),
            new ItemDetails(3,"25Rs GOODAY Biscuit",25.00,"CREAMY")
            ));

    public List<ItemDetails> getItemDetails()
    {
        return itemDetailsList;
    }
    public ItemDetails getSingleItem(Integer id) {
        return itemDetailsList.stream().filter(n->n.getItemId().equals(id)).findFirst().get();
    }

    public ItemResponse addSingleItem(ItemDetails itemDetails) {
        itemDetailsList.add(itemDetails);
        ItemResponse itemResponse = new ItemResponse();
        itemResponse.setMessage("Item added successfully");
        return itemResponse;
    }
}

Answer 2

You must define the ItemResponse bean in your application:

Start by adding the @Component notation in the ItemResponse class as follows:

@Component
public class ItemResponse {
    private String message;

    //** Default Constructor 
    public ItemResponse() {
    }

    //** getter and setter
}

And in somewhere in a class configuration you have to tell spring that ItemResponse is a bean that will need to be injected. If you have a class with the @Configuration notation declare your bean otherwise create a configuration class for example in a package named "config":

@Configuration
public class AppConfig {

    @Bean
    public ItemResponse itemResponse() {
        return new ItemResponse() ;
    }

}

And don't forget to put a default Constructor in your bean. Good luck !