java - 如何编写Json Web服务从Java中的数据库表中获取相应的数据

Question

这是我的代码:

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;
        }
    }

}

这个类正在获取数据库表的数据并转换为json格式:

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;
    }

}

封装型号；

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;
}

}

还有一类我们已经获得了设定值。我能够使用此 URL 以 Json 格式显示所有数据库表值，但我希望当我传递 id 时:

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

那么它应该只显示id一个对应的名称，标题，url。我尝试过使用这个

http://www.9lessons.info/2012/10/restful-web-services-json-api.html示例但无法执行此操作请帮助我

Answer 1

您必须在 feed 方法参数中添加 @QueryParam("id") String id 并获取 id 的值和根据id的值执行操作并返回JSON字符串。请看下面

   @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，通过传递Connection类型的参数来调用Project类的GetFeeds方法。修改为添加String类型的参数来传递QueryParam中id的值，然后修改查询如下

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

希望这能清楚地解释一切。这将仅返回具有在查询字符串中传递的 ID 值的行。