grails - 在grails中将新项插入 “hasMany”对象时对其执行操作

我是Grails的新手，正在创建我的第一个应用程序，并且发现事情发生的地方有些麻烦，因此，我有一个对象“cicle”，其中包含许多“测量”，并且分别由测量 Controller 创建当我创建一个新的“度量”时，这是在另一台计算机上发生的，这是在同一台计算机上发生的，cicle的某些属性发生了变化，因此，我在cicle中执行了一个名为updateCalculations的方法，该方法需要新创建的度量的数据。

因此，在measurementController中，我试图使用循环中的测量值执行一些操作，但是我得到了空指针异常，我猜想未创建cicle，因此我将操作移至方法之后，将其插入Measurement对象中一个我认为更适合的地方这种方法需要开发，但是我在这里遇到了同样的问题，我什至认为创建cicle时购买了一些未初始化的度量，我不知道真正发生了什么，所以您能帮我吗？

这是我的代码:

测量方法

class Measurement{

String machine
int time1
int time2
int time3
int cicleValue

static belongsTo = [cicle: Cicle]

static constraints = {
    machine blank:false
    time1 nullable:false
    time1 min:0
    time2 nullable:false
    time2 min:0
    time3 nullable:false
    time3 min:0
    cicleValue nullable:false
    cicleValue min:0
}

def afterInsert(){
    this.cicle.updateCalculations()
}

public void updateCicleValue(){
    double avgTime = (time1 + time2 + time3)/3
    cicleValue = 30 * 24 * 60 * 60 / avgTime
}
}

Cicle.groovy

class Cicle {

String machine
int cicleValue

static hasMany = [measurements:Measurement]

static constraints = {
    machine blank:false
    cicleValue nullable:false
}

public void updateCalculations(){

    int sumCicles = 0

    measurements.each{ measurement ->
        sumCicles += measurement.cicleValue
    }

    cicleValue = sumCicles / measurements.size()
    this.save(failOnError: true)
}
}

MeasurementController.groovy

@Transactional(readOnly = true)
class MeasurementController {

static allowedMethods = [save: "POST", update: "PUT", delete: "DELETE"]

def create() {
    respond new Measurement(params)
}

@Transactional
def save(Measurement measurementInstance) {
if (measurementInstance == null) {
        notFound()
        return
    }

measurementInstance.updateCicleValue()

    Cicle cicle = Cicle.findByMachine(measurementInstance.machine)

    if(cicle == null){
        cicle = new Cicle(machine: measurementInstance.machine, cicleValue: measurementInstance.cicleValue)
        cicle.save flush: true
    }

    measurementInstance.cicle = cicle

    measurementInstance.validate()

    if (measurementInstance.hasErrors()) {
        respond measurementInstance.errors, view:'create'
        return
    }

    measurementInstance.save flush:true
    cicle.measurements << measurementInstance
    cicle.save flush: true

    request.withFormat {
        form multipartForm {
            flash.message = message(code: 'default.created.message', args: [message(code: 'measurementInstance.label', default: 'Measurement'), measurementInstance.id])
            redirect measurementInstance
        }
        '*' { respond measurementInstance, [status: CREATED] }
    }
}

protected void notFound() {
    request.withFormat {
        form multipartForm {
            flash.message = message(code: 'default.not.found.message', args: [message(code: 'measurementInstance.label', default: 'Measurement'), params.id])
            redirect action: "index", method: "GET"
        }
        '*'{ render status: NOT_FOUND }
    }
}
}

这是来自控制台的堆栈跟踪:

|Loading Grails 2.3.7
|Configuring classpath
.
|Environment set to development
.................................
|Packaging Grails application
...........
|Compiling 1 source files
...............................
|Running Grails application
|Server running. Browse to http://localhost:8080/mock-app
....Error
|
2014-04-24 21:51:34,719 [http-bio-8080-exec-3] ERROR errors.GrailsExceptionResolver  - NullPointerException occurred when processing request: [POST] /mock-app/measurement/save - parameters:
time3: 20
time2: 20
time1: 20
machine: 2-12
create: Crear
Cannot invoke method size() on null object. Stacktrace follows:
Message: Cannot invoke method size() on null object
    Line | Method
->>   23 | updateCalculations in com.rpc.mock.app.Cicle
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|     26 | afterInsert        in com.rpc.mock.app.Measurement
|    153 | call . . . . . . . in org.grails.datastore.gorm.support.EventTriggerCaller$MethodCaller
|     96 | call               in org.grails.datastore.gorm.support.EventTriggerCaller
|     47 | onApplicationEvent in org.grails.datastore.mapping.engine.event.AbstractPersistenceEventListener
|     51 | $tt__save          in com.rpc.mock.app.MeasurementController
|    200 | doFilter . . . . . in grails.plugin.cache.web.filter.PageFragmentCachingFilter
|     63 | doFilter           in grails.plugin.cache.web.filter.AbstractFilter
|   1145 | runWorker . . . .  in java.util.concurrent.ThreadPoolExecutor
|    615 | run                in java.util.concurrent.ThreadPoolExecutor$Worker
^    744 | run . . . . . . .  in java.lang.Thread

它停在afterUpdate方法中，告诉测量其null

任何帮助都会很棒

谢谢

最佳答案

这是因为您忘记将measurementInstance添加到cicle.measurements。
尝试在此处保存cicle实例时添加它:

 if(cicle == null){
        cicle = new Cicle(machine: measurementInstance.machine, cicleValue: measurementInstance.cicleValue)
        cicle.addToMeasurements(measurementInstance)    //add to collection
        cicle.save flush: true
    }