反射通用获取字段值

本文介绍了反射通用获取字段值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在尝试通过反射获取字段的值.问题是我不知道字段的类型，必须在获取值时决定它.

I am trying to obtain a field's value via reflection. The problem is I don't know the field's type and have to decide it while getting the value.

此代码导致此异常:

无法将 java.lang.String 字段 com....fieldName 设置为 java.lang.String

Can not set java.lang.String field com....fieldName to java.lang.String

Field field = object.getClass().getDeclaredField(fieldName); field.setAccessible(true); Class<?> targetType = field.getType(); Object objectValue = targetType.newInstance(); Object value = field.get(objectValue);

我尝试投射，但出现编译错误:

I tried to cast, but I get compilation errors:

field.get((targetType)objectValue)

或

targetType objectValue = targetType.newInstance();

我该怎么做?

推荐答案

像之前回答的一样，你应该使用:

Like answered before, you should use:

Object value = field.get(objectInstance);

另一种有时更受欢迎的方法是动态调用 getter.示例代码:

Another way, which is sometimes prefered, is calling the getter dynamically. example code:

public static Object runGetter(Field field, BaseValidationObject o) { // MZ: Find the correct method for (Method method : o.getMethods()) { if ((method.getName().startsWith("get")) && (method.getName().length() == (field.getName().length() + 3))) { if (method.getName().toLowerCase().endsWith(field.getName().toLowerCase())) { // MZ: Method found, run it try { return method.invoke(o); } catch (IllegalAccessException e) { Logger.fatal("Could not determine method: " + method.getName()); } catch (InvocationTargetException e) { Logger.fatal("Could not determine method: " + method.getName()); } } } } return null; }

还要注意，当你的类从另一个类继承时，你需要递归地确定Field.例如，获取给定类的所有字段；

Also be aware that when your class inherits from another class, you need to recursively determine the Field. for instance, to fetch all Fields of a given class;

for (Class<?> c = someClass; c != null; c = c.getSuperclass()) { Field[] fields = c.getDeclaredFields(); for (Field classField : fields) { result.add(classField); } }