我的 function 在 java 项目中工作时在 spring 启动项目中不起作用

Question

    @Override
    public Song nextSong(Long playlistId, Long songId) {
        String sql = "SELECT s.id, s.genre, s.artist_name, s.track_name, s.duration_ms, s.popularity "
                + "FROM T_SONGPLAYLIST AS sp INNER JOIN T_SONGS AS s "
                + "ON s.id = sp.song_id "
                + "WHERE sp.playlist_id = ? ";
        List<Song> songs = new ArrayList();
        songs = jdbcTemplate.query(sql,rowMapperSong,playlistId);
        

        return gettingIt(songs, songId);
        
        

这是 PlayerRepositoryJDBCImpl.java 文件中的方法

public Song gettingIt(List<Song> songs, Long songId) {
        
        DoublyLinkedList d = new DoublyLinkedList(songs);
        d.display();
        int index = -1;
        for(int i = 0; i<songs.size();i++)
        {
            if(songId == d.takeNodebyIndex(i).getdata().getId()) {
                System.out.println(d.takeNodebyIndex(i).getdata().getId());
                index = i+1;
            }
        }
            
        return d.takeNodebyIndex(index).getdata();
    }
}

我正在使用此映射发送获取请求：

@RequestMapping(method=RequestMethod.GET, value ="/nextSong/{playlistId}-{songId}")

当我使用 nextSong 方法向链接的 url 发送获取请求时，它返回给我这些 output：

[2m2021-05-28 16:47:45.364[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[  restartedMain][0;39m [36mo.s.b.w.embedded.tomcat.TomcatWebServer [0;39m [2m:[0;39m Tomcat started on port(s): 8080 (http) with context path ''
[2m2021-05-28 16:47:45.365[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[  restartedMain][0;39m [36mc.d.musicplayer.MusicPlayerApplication  [0;39m [2m:[0;39m Started MusicPlayerApplication in 2.187 seconds (JVM running for 403.063)
[2m2021-05-28 16:47:45.368[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[  restartedMain][0;39m [36m.ConditionEvaluationDeltaLoggingListener[0;39m [2m:[0;39m Condition evaluation unchanged
[2m2021-05-28 16:47:46.504[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.a.c.c.C.[Tomcat].[localhost].[/]      [0;39m [2m:[0;39m Initializing Spring FrameworkServlet 'dispatcherServlet'
[2m2021-05-28 16:47:46.504[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.s.web.servlet.DispatcherServlet       [0;39m [2m:[0;39m FrameworkServlet 'dispatcherServlet': initialization started
[2m2021-05-28 16:47:46.508[0;39m [32m INFO[0;39m [35m14892[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.s.web.servlet.DispatcherServlet       [0;39m [2m:[0;39m FrameworkServlet 'dispatcherServlet': initialization completed in 4 ms
[Song [id=154, genre=Dance, artist_name=2NE1, track_name=COME BACK HOME, duration_ms=229627, popularity=57] Song [id=524, genre=Electronic, artist_name=Flux Pavilion, track_name=I Can t Stop, duration_ms=305786, popularity=56]  Song [id=1514, genre=Reggae, artist_name=Don Carlos, track_name=English Women, duration_ms=182933, popularity=32]   ]
[Song [id=154, genre=Dance, artist_name=2NE1, track_name=COME BACK HOME, duration_ms=229627, popularity=57] Song [id=524, genre=Electronic, artist_name=Flux Pavilion, track_name=I Can t Stop, duration_ms=305786, popularity=56]  Song [id=1514, genre=Reggae, artist_name=Don Carlos, track_name=English Women, duration_ms=182933, popularity=32]   ]

这是双向链表方法：

package com.dataStructuresProject.musicplayer.model;

import java.util.List;

public class DoublyLinkedList {

    private Node head;
    private Node tail;
    private int length;

    public DoublyLinkedList(List<Song> arr) {
        this.head = null;
        this.tail = null;
        this.length = 0;
        for (int i=0;i<arr.size();i++)
            this.add(arr.get(i));
    }
    public int getLength() {
        return length;
    }
    public void add(Song data)
    {
        Node temp = new Node(data);
        if(head == null)
            head = temp;
        else
        {
            Node iter = head;
            while (iter.next != null)
                iter = iter.next;

            iter.next = temp;
            temp.prev = iter;
            tail = temp;
        }

        this.length++;
    }

    public void display()
    {
        Node iter = head;
        System.out.print("[");
        while(iter != null)
        {
            System.out.print(iter.data+"\t");
            iter = iter.next;
        }
        System.out.println("]");
    }
    public void reverseDisplay()
    {
        Node iter = tail;
        System.out.print("[");
        while(iter != null)
        {
            System.out.print(iter.data+"\t");
            iter = iter.prev;
        }
        System.out.println("]");
    }
    public Node takeNodebyIndex(int i)
    {
        Node iter = head;
        int iteratorIndex;

        iteratorIndex = 0;
        while(iteratorIndex++<i)
            iter = iter.next;


        return iter;
    }
    public class Node {
        Song data;
        private Node next;
        private Node prev;

        public Node(Song data)
        {
            this.data = data;
            this.next = null;
            this.prev = null;
        }
        public Node() {
            this.next = null;
            this.prev = null;
        }
        public Node(Node prev, Node next) {
            this.next = next;
            this.prev = prev;
        }
        public Song getdata() {
            return this.data;
        }
    }
}

最后，如果我使用 http://localhost:8080/api/nextSong/2-154 url 发送 get 请求，该方法必须返回 id 为 524 的歌曲，但它总是返回双向链表的第一首歌曲.

Answer 1

因为您没有中断条件：

    for(int i = 0; i<songs.size();i++)
    {
        if(songId == d.takeNodebyIndex(i).getdata().getId()) {
            System.out.println(d.takeNodebyIndex(i).getdata().getId());
            index = i+1;
            break; // this should be added here
        }
    }

Answer 2

实际上，我通过在比较它们时将双链表中的 songId 和 id 都转换为字符串变量来解决问题。 我不知道是什么导致了这个问题，但是转换字符串对我有用。