grails - Grails 'Cannot issue a redirect'问题

Question

正在发生以下问题:

def someAction() {
    ...
    if (someCondition)
        redirect action: 'index'
        return
    }

    if (someOtherCondition)
        redirect action: 'index'
        return
    }

    ...

    redirect action: 'success'
}

这很完美。但是，一旦我将其包装在交易中:

def someAction() {
    MyDomainClass.withTransaction { status ->

        if (someCondition)
            status.setRollbackOnly()
            redirect action: 'index'
            return
        }

        if (someOtherCondition)
            status.setRollbackOnly()
            redirect action: 'index'
            return
        }

        ...

    }

    redirect action: 'success'
}

这将引发异常:

Cannot issue a redirect(..) here. The response has already been committed either by another redirect or by directly writing to the response.. Stacktrace follows: Message: Cannot issue a redirect(..) here. The response has already been committed either by another redirect or by directly writing to the response.

奇怪的是，我在另一段代码中做的完全一样，而且效果很好。唯一的区别是我链接而不是重定向。我在上面的代码中尝试了链接，但是仍然抛出异常。

Answer 1

此return来自:

MyDomainClass.withTransaction { status ->

        if (someCondition)
            status.setRollbackOnly()
            redirect action: 'index'
            return   //   <-- !!! this one !!!
        }
}

从封闭块，而不是从行动返回您。因此，它调用 redirect action: 'index'，从闭包退出，然后在执行块之后执行另一个重定向:

redirect action: 'success'

最后一个导致此异常。

解决方法是，您可以记住重定向状态并检查最后一步，例如:

boolean redirected = false
MyDomainClass.withTransaction { status ->

        if (someCondition)
            status.setRollbackOnly()
            redirected = true
            redirect action: 'index'
            return
        }
}
if (!redirected) { 
    redirect action: 'success'
}

或只是检查响应是否尚未提交(但这种方式似乎有点不可靠):

if (!response.commited) {
    redirect action: 'success'
}