Java 将配置 class 保存到可编辑文件中

Question

您好，我想保存一个 Java class，其中包含我的应用程序的一些配置示例：

class MyConfig {
 public int a= 0;
 public boolean b= true;
}

而且我希望这个文件可以被用户编辑，乍一看 JSONSerializer 对于一个简单的案例来说是可以的。但我想要更多...例如，将来我想从我的 class 添加/删除字段...它仍然有效吗？（如果添加了一个字段，我希望在加载包含旧 class 的文件时使用默认值......）

不知道我说清楚没有... 但是如果我可以添加

public String c= "hello";

然后加载文件（不包含字段 c 的值）。谢谢！

编辑：这就是我正在尝试的：

public class PropertiesSerializer<T> {
    private final Class clDef;
    private T obj;

    public T get(){ return obj; }

    public PropertiesSerializer(Class cl){ //uhm...
        if ( cl == null ) throw new NullPointerException();
        clDef= cl;
    }

    public void init() throws InstantiationException {
        Constructor[] ctors = clDef.getDeclaredConstructors();
        Constructor ctor = null;
        for (int i = 0; i < ctors.length; i++) {
            ctor = ctors[i];
            if (ctor.getGenericParameterTypes().length == 0)
                break;
        }

        ctor.setAccessible(true);
        try {
            obj = (T) ctor.newInstance();
        } catch (IllegalAccessException e) {
            throw new InstantiationException(e.getMessage());
        } catch (InvocationTargetException e) {
            throw new InstantiationException(e.getMessage());
        }
    }

    public void load(String filename) throws IOException, InstantiationException {
        File fl= new File(filename);
        Properties props= new Properties();
        try (FileReader reader= new FileReader(fl)) {
            props.load(reader);
        }

        init();
        for(Field fd: clDef.getFields()){
            try {
                Object valobj= props.getProperty( fd.getName() );
                obj.getClass().getField( fd.getName() ).set( obj, fd.getType().cast(valobj) ); //uhm...
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (NoSuchFieldException e) {
                e.printStackTrace();
            }
        }
    }

    public void save(String filename) throws InvalidStateException, IllegalAccessException, IOException {
        if( obj == null ) throw new InvalidStateException("init wasn't called!");

        File fl= new File(filename);
        Properties prop= new Properties();
        for( Field fd: clDef.getFields() ){
            prop.setProperty( fd.getName(), String.valueOf(fd.get(obj)) ); //uhm...
        }

        try( FileWriter writer = new FileWriter(fl) ) {
            prop.store(writer, "PropertiesSerializer");
        }
    }
}

当然我可以保存我的测试class...

public class TestClass implements Serializable {
    public boolean a= true;
    //public int i= 1;
}

但我无法加载 :( 失败：

Exception in thread "main" java.lang.ClassCastException: Cannot cast java.lang.String to boolean at java.lang.Class.cast(Class.java:3369) at net.sf.aldrigo.propertiesSerializer.PropertiesSerializer.load(PropertiesSerializer.java:55) at net.sf.aldrigo.propertiesSerializer.MainTest.main(MainTest.java:17) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Answer 1

要么查看 SimpleXml or just use java.util.Properties 并通过 Reflection 自己滚动。

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