java - 从 GSON 到 Json 的大规模 StackOverflowError

Question

所以我尝试使用 GSON 通过 toJson() 函数将类转换为 JSON 文件，每次调用代码时都会出现 1000 多行的 StackOverflowError。这是错误:http://pastebin.com/dBhYUFva

这是我正在执行 gson.toJson() 的类(class):

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import mc.kwit.arena.players.ArenaPlayer;
import mc.kwit.arena.util.PlayerUtil;
import org.bukkit.Bukkit;
import org.bukkit.ChatColor;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Zach on 8/3/16.
 */
public class Match {

    List<ArenaPlayer> arenaPlayers = new ArrayList<ArenaPlayer>();
    String[] uuidArray = null;
    Player winner;
    String matchId = "123456";
    int killLimit = 5;
    int timeLimit = -1;


    public Match() {

    }

    public Match(List<ArenaPlayer> arenaPlayerList, String id, int seconds, int kills) {
        this.arenaPlayers = arenaPlayerList;
        this.matchId = id;
        this.timeLimit = seconds;
        this.killLimit = kills;
    }

    public Match(String[] players, String id, int seconds, int kills) {
        this.uuidArray = players;
        this.matchId = id;
        this.timeLimit = seconds;
        this.killLimit = kills;
    }

    public void start() {

        //Create our ArenaPlayer objects
        this.arenaPlayers = PlayerUtil.uuidToArenaPlayerList(uuidArray);

        Bukkit.getLogger().info("Match \" " + this.matchId + "\" has been started!");
        //Whitelist all participants
        for(ArenaPlayer p : arenaPlayers) {
            KwitArena.pc.addArenaPlayer(p.getPlayer());
            p.getPlayer().setWhitelisted(true);
            Bukkit.getLogger().info(p.getName() + " has been whitelisted!");
            p.setMatch(this);
        }
    }

    public void finish() throws Exception {

        //Remove all players from whitelist and game
        for(ArenaPlayer p : arenaPlayers) {
            p.getPlayer().setWhitelisted(false);

            if(p.isWinner()){
                p.kick(ChatColor.GREEN + "You have won the game!");
                this.winner = p.getPlayer();
            } else {
                p.kick(ChatColor.RED + winner.getName() + "has won the game :(");
            }
        }

        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        String stats = gson.toJson(this);
        KwitArena.postStats(stats);

        //Remove this arena instance from the plugin
        KwitArena.match = null;
    }

    public String getId(){
        return(this.matchId);
    }

    public void setWinner(ArenaPlayer p) {
        this.winner = p.getPlayer();
    }
}

ArenaPlayer.class:

import mc.kwit.arena.Match;
import org.bukkit.OfflinePlayer;
import org.bukkit.entity.Player;

/**
 * Created by Zach on 7/31/16.
 */
public class ArenaPlayer {

    ArenaPlayer ap;
    Player  player;
    OfflinePlayer offlinePlayer;
    int kills = 0;
    int deaths = 0;
    boolean isInGame = false;
    Match match = null;
    boolean isWinner = false;

    public ArenaPlayer(Player player){
        this.player = player;
    }

    public ArenaPlayer(Player player, boolean playing, int numKills, int numDeaths) {
        this.player = player;
        kills = numKills;
        deaths = numDeaths;
        isInGame = playing;
    }


    //Getters
    public String getMatchId() { return(this.match.getId());}

    public int getKills() { return(this.kills);}

    public int getDeaths() { return(this.deaths);}

    public Match getMatch() { return(this.match);}

    public Player getPlayer() { return(this.player);}

    public String getName() { return(player.getName());}

    public OfflinePlayer getOfflinePlayer() { return(this.offlinePlayer);}

    //Setters
    public void setMatch(Match match) { this.match = match;}

    public void setIsWinner(boolean b) { this.isWinner = b;}

    public void setOfflinePlayer(OfflinePlayer off) { this.offlinePlayer = off; }


    //Extras
    public void addDeath() { this.deaths++;}

    public void addKill() { this.kills++;}

    public boolean isPlaying() { return(this.isInGame);}

    public boolean isWinner() { return(this.isWinner);}

    public void kick(String message) { player.kickPlayer(message);}


}

我不太确定从哪里开始堆栈跟踪，有人有一些指示吗？

Answer 1

我认为问题在于 Match 有一个 ArenaPlayer 字段，而 ArenaPlayer 有一个 Match 字段，如果两个实例相互引用，则会导致 Gson 由于其实现而进入无限循环。

您必须整理您的类、实例，或使用不同的库，或从序列化中排除某些字段 - 请参阅 Gson doc .

<小时/>

顺便说一句，1000 是默认的调用堆栈深度 - 如果您在堆栈中看到这么多行，则可能遇到了无限递归。