如何編寫Json Web服務以從Java中的數據庫表中獲取核心數據

Question

這是我的代碼：

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;

import dto.FeedObjects;


public class Project {


    public ArrayList<FeedObjects> GetFeeds(Connection connection) throws Exception
    {
        ArrayList<FeedObjects> feedData = new ArrayList<FeedObjects>();
        try
        {
            //String uname = request.getParameter("uname");
            PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website ORDER BY id DESC");
            //ps.setString(1,uname);
            ResultSet rs = ps.executeQuery();
            while(rs.next())
            {
                FeedObjects feedObject = new FeedObjects();
                feedObject.SetId(rs.getInt("id"));
                feedObject.setTitle(rs.getString("title"));
                feedObject.setDescription(rs.getString("description"));
                feedObject.setUrl(rs.getString("url"));
                feedData.add(feedObject);
            }
            return feedData;
        }
        catch(Exception e)
        {
            throw e;
        }
    }

}

此類獲取數據庫表的數據並以json格式轉換：

package webService;

import java.util.ArrayList;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

import model.ProjectManager;

import com.google.gson.Gson;

import dto.FeedObjects;

@Path("/WebService")
public class FeedService {

    @GET
    @Path("/GetFeeds")
    @Produces("application/json")
    public String feed() {
        String feeds = null;
        try {
            ArrayList<FeedObjects> feedData = null;
            ProjectManager projectManager = new ProjectManager();
            feedData = projectManager.GetFeeds();
            Gson gson = new Gson();
            feeds = gson.toJson(feedData);

        } catch (Exception e) {
            System.out.println("error");
        }
        return feeds;
    }

}

包裝型號；

import java.sql.Connection;
import java.util.ArrayList;

import dao.Database;

import dao.Project;
import dto.FeedObjects;

public class ProjectManager {


public ArrayList<FeedObjects> GetFeeds(String id)throws Exception {
    ArrayList<FeedObjects> feeds = null;
    try {
            Database database= new Database();
            Connection connection = database.Get_Connection();
            Project project= new Project();
            feeds=project.GetFeeds(connection);

    } catch (Exception e) {
        throw e;
    }
    return feeds;
}

}

還有另一類可以獲取設置值的類。 我可以使用此URL以Json格式顯示所有數據庫表值，但是我希望在傳遞id時：

http://localhost:8080/RESTfulProject/REST/WebService/GetFeeds?id=1  

那么它應該僅顯示一個ID對應的名稱，標題，URL。 我試過用這個

http://www.9lessons.info/2012/10/restful-web-services-json-api.html示例但無法執行此操作請幫助我

Answer 1

您必須在feed方法參數中添加@QueryParam("id") String id ，並獲取ID的值，然后根據ID的值執行操作，然后返回JSON字符串。請查看以下內容

   @GET
    @Path("/GetFeeds")
    @Produces("application/json")
    public String feed(@QueryParam("id") String id) {
        String feeds = null;
        try {
            ArrayList<FeedObjects> feedData = null;
            ProjectManager projectManager = new ProjectManager();
            // Modify the GetFeeds method by sending the value of id
            // and prepare feed data based on id
            feedData = projectManager.GetFeeds(id);
            Gson gson = new Gson();
            // create the json data for the feed data of the corresponding id value
            feeds = gson.toJson(feedData);

        } catch (Exception e) {
            System.out.println("error");
        }
        return feeds;

   }

在ProjectManager的GetFeeds方法中，通過傳遞Connection類型的參數來調用Project類的GetFeeds方法。 對其進行修改以添加String類型的參數以從QueryParam傳遞id的值，然后按如下所示修改查詢

SELECT id,title,description,url FROM website where id = 'ID_VALUE_IN_QUERY_PARAM'

希望這清楚地解釋了一切。 這將僅返回ID值在查詢字符串中傳遞的行。