---
title: 'Springboot 查詢的 restfulapi(不使用資料庫)'
disqus: hackmd
---
###### tags: `SpringBoot`
Springboot 查詢的 restfulapi(不使用資料庫)
===

[TOC]

## 筆記目的

完成一個專案，讓你輸入某個網址，就得到對應的json格式的資料

具體請參考:

* [新手工程師](https://chikuwa-tech-study.blogspot.com/2021/05/spring-boot-three-tier-architecture.html)

## 注意事項

由於是簡單的專案，所以尚未去串接資料庫，所以一旦關掉程式，對應的資料也會不見請注意
由於專案簡單，所以先忽略service的部分

## 程式碼部分

### 專案架構


### pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.5.3</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>helloworld</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>helloworld</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
					<excludes>
						<exclude>
							<groupId>org.projectlombok</groupId>
							<artifactId>lombok</artifactId>
						</exclude>
					</excludes>
				</configuration>
			</plugin>
		</plugins>
	</build>

</project>

### Product (Bean)

package com.example.demo.entity;

public class Product {
	 private String id;
	    private String name;
	    private int price;

	    public Product() {

	    }

	    public Product(String id, String name, int price) {
	        this.id = id;
	        this.name = name;
	        this.price = price;
	    }

	    public String getId() {
	        return id;
	    }

	    public void setId(String id) {
	        this.id = id;
	    }

	    public String getName() {
	        return name;
	    }

	    public void setName(String name) {
	        this.name = name;
	    }

	    public int getPrice() {
	        return price;
	    }

	    public void setPrice(int price) {
	        this.price = price;
	    }
}

### DemoProductDAO

package com.example.demo.dao;

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

import javax.annotation.PostConstruct;

import org.springframework.stereotype.Repository;
import com.example.demo.entity.*;
@Repository
public class DemoProductDAO {

	 private final List<Product> productDB = new ArrayList<>();

	    @PostConstruct
	    private void initDB() {
	        productDB.add(new Product("B0001", "Android Development (Java)", 380));
	        productDB.add(new Product("B0002", "Android Development (Kotlin)", 420));
	        productDB.add(new Product("B0003", "Data Structure (Java)", 250));
	        productDB.add(new Product("B0004", "Finance Management", 450));
	        productDB.add(new Product("B0005", "Human Resource Management", 330));
	    }

	    public Product insert(Product product) {
	        productDB.add(product);
	        return product;
	    }
	    public  List<Product> showallProduct( ) {
	    	return productDB;
	    }
}

### DemoController

package com.example.demo.controller;

import java.util.List;

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

import com.example.demo.dao.DemoProductDAO;
import com.example.demo.entity.Product;

@RestController
public class DemoController {
	@Autowired
	private DemoProductDAO demoProductDAO;

    @RequestMapping(value = "/demo", method = RequestMethod.GET)
    public String demo(){
        return "Hello World!";
    }
    @RequestMapping(value = "/showallProduct", method = RequestMethod.GET)
    public List<Product> showallProduct(){
    
    	return demoProductDAO.showallProduct();
    }
    
    
}

### 專案解析

Product 這個class基本上就只是定義身為一個產品該要有的三個要素各為何，基本上只是設計圖

DemoProductDAO 幫助了我們去initialize資料，加入的`@PostConstruct`註解會幫助我們在執行專案時，自動去執行這段程式碼

關鍵點其實在

 public  List<Product> showallProduct( ) {
	    	return productDB;
	    }

此函數直接返回了`productDB`這個每個元素都是`Product`的**List**

DemoController 幫助我們控管url這件事，任何使用者只要使用get訪問了/showallProduct，就會執行這個showallProduct函數，他利用了已經被Autowird過的demoProductDAO來執行showallProduct這個函數

 @RequestMapping(value = "/showallProduct", method = RequestMethod.GET)
    public List<Product> showallProduct(){
    
    	return demoProductDAO.showallProduct();
    }

### 如何執行專案

在瀏覽器上輸入

http://localhost:8080/showallProduct

就可以得到對應的資料

## 專案結果截圖