Java构造函数中this引用的限制与循环依赖解决方案

// OptionType 枚举 (假设存在)
enum OptionType {
    STRING, INTEGER, BOOLEAN
}

// 抽象父类 Command
public abstract class Command {
    private final String SETTINGS_PATH;
    private final List<ParameterData> PARAMETERS;

    public Command(String settingsPath, List<ParameterData> parameters) {
        this.SETTINGS_PATH = settingsPath;
        this.PARAMETERS = parameters;
    }

    public String getSettingsPath() {
        return SETTINGS_PATH;
    }

    public abstract void run();
}

// 数据类 ParameterData
public class ParameterData {
    private final String SETTINGS_KEY;
    private final Command COMMAND; // 持有 Command 引用
    private final OptionType OPTION_TYPE;
    private final boolean REQUIRED;

    public ParameterData(String settingsKey, Command command, OptionType optionType, boolean required) {
        this.SETTINGS_KEY = settingsKey;
        this.COMMAND = command;
        this.OPTION_TYPE = optionType;
        this.REQUIRED = required;
    }

    public String getSettingsKey() {
        return SETTINGS_KEY;
    }

    public String getSettingsPath() {
        return COMMAND.getSettingsPath() + ".Parameters." + SETTINGS_KEY;
    }

    // ... 其他 getter 方法
}

// 继承类 TestCommand (出现错误)
public class TestCommand extends Command {
    public TestCommand() {
        // 编译错误: "Cannot reference 'this' before supertype constructor has been called"
        super("Settings.TestCommand",
                List.of(new ParameterData("SettingsKey", this, OptionType.STRING, true)));
    }

    @Override
    public void run() {
        // do something
    }
}

public class ParameterData {
    private final String SETTINGS_KEY;
    private Command COMMAND; // 不再是 final
    private final OptionType OPTION_TYPE;
    private final boolean REQUIRED;

    // 构造器不再接收 Command 引用
    public ParameterData(String settingsKey, OptionType optionType, boolean required) {
        this.SETTINGS_KEY = settingsKey;
        this.OPTION_TYPE = optionType;
        this.REQUIRED = required;
    }

    // 包私有方法，用于在 Command 对象完全构建后设置其引用
    void setCommand(Command command) {
        if (this.COMMAND != null) {
            throw new IllegalStateException("Command 引用已被设置，不允许重复设置。");
        }
        this.COMMAND = command;
    }

    public String getSettingsKey() {
        return SETTINGS_KEY;
    }

    public String getSettingsPath() {
        if (COMMAND == null) {
            // 如果在调用此方法时 Command 引用尚未设置，则抛出异常
            throw new IllegalStateException("Command 引用尚未与此 ParameterData 关联: " + SETTINGS_KEY);
        }
        return COMMAND.getSettingsPath() + ".Parameters." + SETTINGS_KEY;
    }

    public OptionType getOptionType() {
        return OPTION_TYPE;
    }

    public boolean isRequired() {
        return REQUIRED;
    }
}

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

public class TestCommand extends Command {
    public TestCommand() {
        // 1. 创建一个可变的 ParameterData 列表
        List<ParameterData> tempParameters = new ArrayList<>();

        // 2. 创建 ParameterData 实例，此时不传入 Command 引用
        ParameterData param1 = new ParameterData("SettingsKey1", OptionType.STRING, true);
        ParameterData param2 = new ParameterData("SettingsKey2", OptionType.INTEGER, false);
        tempParameters.add(param1);
        tempParameters.add(param2);

        // 3. 调用 super() 构造器，传入 ParameterData 列表的不可变副本
        // 此时，TestCommand 的父类部分已完成初始化，'this' 引用变得有效
        super("Settings.TestCommand", List.copyOf(tempParameters));

        // 4. 在 super() 调用之后，'this' 引用有效，现在可以设置 ParameterData 中的 Command 引用
        param1.setCommand(this);
        param2.setCommand(this);
    }

    @Override
    public void run() {
        // 执行命令逻辑
    }
}

public class ParameterData {
    private final String SETTINGS_KEY;
    private final String COMMAND_SETTINGS_PATH; // 直接存储 Command 的 settingsPath
    private final OptionType OPTION_TYPE;
    private final boolean REQUIRED;

    // 构造器接收 Command 的 settingsPath
    public ParameterData(String settingsKey, String commandSettingsPath, OptionType optionType, boolean required) {
        this.SETTINGS_KEY = settingsKey;
        this.COMMAND_SETTINGS_PATH = commandSettingsPath;
        this.OPTION_TYPE = optionType;
        this.REQUIRED = required;
    }

    public String getSettingsPath() {
        // 直接使用存储的 settingsPath
        return COMMAND_SETTINGS_PATH + ".Parameters." + SETTINGS_KEY;
    }
    // ...
}

public class TestCommand extends Command {
    public TestCommand() {
        // 在 super() 调用中，传入 Command 的 settingsPath
        super("Settings.TestCommand",
                List.of(new ParameterData("SettingsKey", "Settings.TestCommand", OptionType.STRING, true)));
    }

    @Override
    public void run() {
        // do something
    }
}

public class ParameterData {
    private final String SETTINGS_KEY;
    private final OptionType OPTION_TYPE;
    private final boolean REQUIRED;

    public ParameterData(String settingsKey, OptionType optionType, boolean required) {
        this.SETTINGS_KEY = settingsKey;
        this.OPTION_TYPE = optionType;
        this.REQUIRED = required;
    }

    // getSettingsPath 方法现在接收 Command 实例作为参数
    public String getSettingsPath(Command command) {
        return command.getSettingsPath() + ".Parameters." + SETTINGS_KEY;
    }
    // ...
}

public class TestCommand extends Command {
    public TestCommand() {
        // Command 构造器不再需要 ParameterData 包含 Command 引用
        super("Settings.TestCommand",
                List.of(new ParameterData("SettingsKey", OptionType.STRING, true)));
    }

    @Override
    public void run() {
        // 当需要 ParameterData 的完整路径时，传入 'this'
        // 例如:
        // ParameterData param = this.getParameters().get(0);
        // String fullPath = param.getSettingsPath(this);
    }
}