java 反射 getDeclaredField和getField的区别

getDeclaredField是可以获取一个类的所有字段.
getField只能获取类的public 字段.

 public Field getDeclaredField(String name)
        throws NoSuchFieldException, SecurityException {
        checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
        Field field = searchFields(privateGetDeclaredFields(false), name);
        if (field == null) {
            throw new NoSuchFieldException(name);
        }
        return field;
    }


private Field getField0(String name) throws NoSuchFieldException {
        Field res = null;
        // Search declared public fields
        if ((res = searchFields(privateGetDeclaredFields(true), name)) != null) {
            return res;
        }
.......

getField其实调用的是getField0.
他们最后都调用了searchFields.
不过getDeclaredField传入的是privateGetDeclaredFields(false),
getField传入的是privateGetDeclaredFields(true),

 private Field[] privateGetDeclaredFields(boolean publicOnly) {
        checkInitted();
        Field[] res = null;
        if (useCaches) {
            clearCachesOnClassRedefinition();
            if (publicOnly) {
                if (declaredPublicFields != null) {
                    res = (Field[]) declaredPublicFields.get();
                }
            } else {
                if (declaredFields != null) {
                    res = (Field[]) declaredFields.get();
                }
            }

可以看到传入条件为true的时候使用的是declaredPublicFields,意思是public字段
为false的时候使用的是declaredFields.

当然declaredFields和declaredPublicFields最终的来源是

 private native Field[]       getDeclaredFields0(boolean publicOnly);

可惜这是个native方法.感觉java就是很无奈,发现都是native方法档在路上.