Spring API 開發簡單示例及技巧

目錄.png

以使用者登入為栗子，示例

API

請求時處理技巧，和

API

傳回資料時如何處理。

一、API傳回時：傳回的json資料

使用

spring mvc

預設配置就可以傳回

json

了，不過需要

jackson

的

jar

包

APIResponse

是一個實體類，配合

@ResponseBody

就會自動轉成

Json

@RequestMapping("user")
@Controller
public class UserController {

    @Resource
    private UserService userService;

    @RequestMapping(value = "/login", method = RequestMethod.POST, headers = "api-version=1")
    public @ResponseBody
    APIResponse login(HttpServletRequest request) {
        return userService.login(new APIRequest(request));
    }

    @RequestMapping(value = "/query", method = RequestMethod.GET, headers = "api-version=1")
    public @ResponseBody
    APIResponse query() {
        return userService.allUsers();
    }
}

           

二、API請求時：提取和解析參數

springMVC

背景控制層提取和解析請求參數的方式主要有兩種

• request.getParameter("name")

  ；
• 通過注解

  @RequestParam

  直接擷取；

1.注解方式：@ResponseBody

// 必傳且參數名為`userName`
@RequestParam String userName

// 必傳且指定參數為 user_name
@RequestParam(value="user_name") String userName

// 辨別是否為必傳，required=false 會給參數指派為null
@RequestParam(value="aa", required=true)
           

完整的如下：

@RequestMapping(method = RequestMethod.GET)
public String setupForm(@RequestParam("user_name") String userName) {
  APIResponse api = new APIResponse();
  api.setUserName(userName);
  ...
   
}
           

value

用來指定要傳入值的

id

名稱

String userName, ModelMap model 是接受 value 傳給的值

2.HttpServletRequest 方式

如果參較多的時候，注解方式可能顯得比較臃腫，這時候也可以使用

HttpServletRequest

提取參數，

request.getParameter("username")

也比較簡單。

這裡着重

Controller

中接收的

HttpServletRequest

做進一步封裝。

APIRequest

對

HttpServletRequest

進一步封裝，提供常用的屬性包括請求的URL、請求參數等。如果提供的屬性不能滿足需求，還提供了原 HttpServletRequest 對象屬性 request。

建立

API

請求的實體類

package com.lugq.web.tools.api;

import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * API請求實體類
 */
public class APIRequest {

    /**
     * Raw Request, 單元測試時為null
     */
    private HttpServletRequest request;

    /**
     * 請求頭
     */
    private Map<String, Object> header;

    /**
     * 請求參數
     */
    private Map<String, Object> params;

    /**
     * 用戶端送出請求時的完整URL
     */
    private String url;

    /**
     * 請求行中的資源名部分
     */
    private String uri;

    /**
     * 請求行中的參數部分
     */
    private String queryString;

    /**
     * 請求方法
     */
    private String method;

    /**
     * 送出請求的客戶機的IP位址
     */
    private String remoteAddr;

    /**
     * 送出請求的客戶機的完整主機名
     */
    private String remoteHost;

    /**
     * 送出請求的客戶機的網絡端口号
     */
    private int remotePort;

    /**
     * WEB伺服器的IP位址
     */
    private String localAddr;

    /**
     * WEB伺服器的主機名
     */
    private String localName;

    /**
     * WEB伺服器的網絡端口号
     */
    private int localPort;

    /**
     * 編碼格式
     */
    private String characterEncoding;

    /**
     * 上下文
     */
    private String contextPath;

    public APIRequest() {
        super();
    }

    public APIRequest(HttpServletRequest request) {

        this.request = request;

        header = new HashMap<String, Object>();
        Enumeration e = request.getHeaderNames();
        while (e.hasMoreElements()) {
            String name = (String) e.nextElement();
            Object value = request.getHeader(name);
            header.put(name, value);
        }

        params = getParamesMap(request.getParameterMap());
        url = request.getRequestURL().toString();
        uri = request.getRequestURI();
        remoteAddr = request.getRemoteAddr();
        remoteHost = request.getRemoteHost();
        remotePort = request.getRemotePort();
        contextPath = request.getContextPath();
        localAddr = request.getLocalAddr();
        characterEncoding = request.getCharacterEncoding();
        localName = request.getLocalName();
        localPort = request.getLocalPort();
        method = request.getMethod();
        queryString = request.getQueryString();
    }

    private Map<String, Object> getParamesMap(Map properties) {
        Map<String, Object> returnMap = new HashMap<String, Object>();
        Iterator entries = properties.entrySet().iterator();
        Map.Entry entry;
        String name;
        String value = "";
        while (entries.hasNext()) {
            entry = (Map.Entry) entries.next();
            name = (String) entry.getKey();
            Object valueObj = entry.getValue();
            if (null == valueObj) {
                value = "";
            } else if (valueObj instanceof String[]) {
                String[] values = (String[]) valueObj;
                for (String v : values) {
                    value = v + ",";
                }
                value = value.substring(0, value.length() - 1);
            } else {
                value = valueObj.toString();
            }
            returnMap.put(name, value);
        }
        return returnMap;
    }

    public Object getParameter(String s) {
        return params.get(s);
    }

    public void setAttribute(String s, Object o) {
        if (params == null) params = new HashMap<String, Object>();
        params.put(s, o.toString());
    }

    // 省略 get set method. 自行補充
    ......
}
           

在控制層

controller

中實作栗子：

@RequestMapping("user")
@Controller
public class UserController {

    @Resource
    private UserService userService;

    @RequestMapping(value = "/login", method = RequestMethod.POST, headers = "api-version=1")
    public @ResponseBody
    APIResponse login(HttpServletRequest request) {
        // 将HttpServletRequest執行個體指派到APIRequest對其進一步封裝
        return userService.login(new APIRequest(request));
    }

}
           

Service 層的邏輯處理如下

@Service
public class UserServiceImpl implements UserService {

    @Resource
    private UserMapper mapper;

    public APIResponse login(APIRequest request) {
        // 擷取請求參數
        String username = (String) request.getParameter("username");
        String password = (String) request.getParameter("password");
        // 處理業務邏輯
        User user = mapper.selectUserByUsername(username);
        APIStatus status = API_SUCCESS;
        if (user == null) {
            status = API_USER_NOT_EXIST;
        } else {
            if (!MD5Util.md5(password).equals(user.getPassword()))
                status = API_USER_PASSWORD_ERROR;
        }
        // 傳回APIResponse對象，配合@ResponseBody轉為Json
        return APIUtil.getResponse(status, user);
    }

    public APIResponse allUsers() {
        List<User> users = mapper.selectAllUser();
        return APIUtil.getResponse(API_SUCCESS, users);
    }
}