java - 如何使 Class.getMethod() 抛出 SecurityException

Question

我有一个实用方法可以为特定字段查找对象的 getter 方法(使用反射):

public static Method findGetter(final Object object, final String fieldName) {
    if( object == null ) {
        throw new NullPointerException("object should not be null");
    } else if( fieldName == null ) {
        throw new NullPointerException("fieldName should not be null");
    }

    String getterName = getMethodNameForField(GET_PREFIX, fieldName);

    Class<?> clazz = object.getClass();
    try {
        return clazz.getMethod(getterName);
    } catch(final NoSuchMethodException e) {
        // exception handling omitted
    } catch(final SecurityException e) {
        // exception handling omitted
    }
}

我想编写一个涵盖 SecurityException 的单元测试场景，但我怎样才能制作getMethod抛出 SecurityException？

javadoc 声明 getMethod 将抛出 SecurityException

If a security manager, s, is present and any of the following conditions is met:

• invocation of s.checkMemberAccess(this, Member.PUBLIC) denies access to the method

• the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class

我更愿意正常触发异常，而不是求助于模拟框架。

Answer 1

System.setSecurityManager(new SecurityManager(){
    @Override
    public void checkMemberAccess(Class<?> clazz, int which) {
        throw new SecurityException("Not allowed")
    }
    @Override
    public void checkPermission(Permission perm) {
        // allow resetting the SM
    }
});
ClassTest.class.getMethod("foo");

记得在 finally block 中调用 System.setSecurityManager(null) 以恢复原始状态。