SpringBoot系列: 與Spring Rest服務交互數據

不管是單體應用還是微服務應用, 現在都流行Restful風格,  下圖是一個比較典型的使用rest的應用架構, 該應用不僅使用database數據源, 而且用到了一個Weather微服務, 另一方面, 該應用也是通過rest方式為web UI 或其他微服務應用提供服務. 

 

 

=============================
通過Postman 插件測試Rest接口
=============================

之前使用postman 插件調試rest接口總報 415 Unsupported Media Type錯誤, 原因是: HEADERS中必須設置Content-type為application/json, 后台才能順利接收到參數. 見下圖截圖. 
{
"timestamp": "2018-09-07T06:49:57.620+0000",
"status": 415,
"error": "Unsupported Media Type",
"message": "Content type 'text/plain;charset=UTF-8' not supported",
"path": "/books"
}

 

 

=============================
與 Rest 服務交互的幾個環節
=============================

一. Spring 后台與其他Rest服務的數據交互
Spring 提供了 RestTemplate 類, 方便和其他Rest服務交互數據

二. 在web response中 返回 json 數據
對於Restful的視圖方法, 其返回類型可以是 ResponseEntity<T> 或者 ResponseEntity<List<T>>, Spring會自動將返回值轉換為json格式. 如果要輸出多個對象的復合體json, 可以在java中定義一個Wrapper類組合多個Pojo類, 然后返回這個Wrapper對象即可.

 

三. 接收 web Request 中的 json 數據
視圖方法的 @RequestBody 注釋參數可以是Map類型, 也可以是Pojo類型. 如果是Pojo類型, Spring就自動完成json->object的轉換, 如果是map類型, Spring就自動完成kv映射. 如果json數據是多個object的某種組合, 我們可以在java中定義一個Wrapper類組合多個Pojo類, 專門接收 Request 中的json數據.

 

=============================
示例代碼
=============================

Pojo代碼:

class Office {
    private String address;

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

class Car {
    private String brand;

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }
}

/*
 * Boss 類是 Office 和 Office 類的組合
 */
class Boss {
    private Car car;
    private Office office;

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public Office getOffice() {
        return office;
    }

    public void setOffice(Office office) {
        this.office = office;
    }
}

 

Controller和主函數代碼:

@SpringBootApplication
@RestController
public class Demo1Application {

    // 示例: 一個對象的json response
    // 測試url為 http://localhost:8080/oneOffice
    // 結果為 {"address":"address1"}
    @ResponseBody
    @RequestMapping(value = "/oneOffice", method = RequestMethod.GET)
    public ResponseEntity<Office> oneOffice() {
        Office office = new Office();
        office.setAddress("address1");
        return new ResponseEntity<Office>(office, HttpStatus.OK);
    }

    // 示例: 一個集合的json response
    // 測試url為 http://localhost:8080/offices
    // 結果為 [{"address":"address1"},{"address":"address2"}]
    @ResponseBody
    @RequestMapping(value = "/offices", method = RequestMethod.GET)
    public ResponseEntity<List<Office>> offices() {
        List<Office> offices = new ArrayList<Office>();
        Office office1 = new Office();
        office1.setAddress("address1");
        Office office2 = new Office();
        office2.setAddress("address2");
        offices.add(office1);
        offices.add(office2);
        return new ResponseEntity<List<Office>>(offices, HttpStatus.OK);
    }

    // 示例: 一個簡單對象的 Post 示例
    // 測試url為 http://localhost:8080/offices
    // 提交的data為  { "address": "address1" }
    @RequestMapping(value = "/offices", method = RequestMethod.POST, consumes = "application/json")
    @ResponseBody
    public String createOffice(@RequestBody Office office) {
        if (office != null && office.getAddress() != null) {
            return "OK";
        } else {
            return "Empty";
        }
    }

    // 示例: 一個組合對象的 response 示例
    // 測試url為  http://localhost:8080/oneBoss
    // 結果為  {"car":null,"office":{"address":"address1"}}
    @RequestMapping(value = "/oneBoss", method = RequestMethod.GET)
    @ResponseBody
    public ResponseEntity<Boss> oneBoss() {
        Office office = new Office();
        office.setAddress("address1");
        Boss objectWrapper = new Boss();
        objectWrapper.setOffice(office);
        return new ResponseEntity<Boss>(objectWrapper, HttpStatus.OK);
    }


    // 示例: 一個組合對象的 Post 示例
    // 測試url為 http://localhost:8080/bosses
    // 提交的data為  {"car":null,"office":{"address":"address1"}}
    @RequestMapping(value = "/bosses", method = RequestMethod.POST, consumes = "application/json")
    @ResponseBody
    public String createBoss(@RequestBody Boss boss) {
        if (boss != null && boss.getOffice() != null
                && boss.getOffice().getAddress() != null) {
            return "OK";
        } else {
            return "Empty";
        }
    }


    public static void main(String[] args) {
        SpringApplication.run(Demo1Application.class, args);
    }
}

 

 

=========================
參考
=========================
https://www.leveluplunch.com/java/tutorials/014-post-json-to-spring-rest-webservice/
https://javabeat.net/rest-api-best-practices/
https://www.baeldung.com/building-a-restful-web-service-with-spring-and-java-based-configuration
截圖來自: https://github.com/hamvocke/testing-microservices-ebook/blob/master/testing-microservices.adoc