Grails JSON数组 [英] Grails JSON array

问题描述

我将Foo对象列表转换为JSON字符串。我需要将JSON字符串解析回Foos列表。然而在下面的例子中，解析给了我一个JSONObjects列表，而不是Foos。

示例

  List list = [new Foo（first），new Foo（second）] 
 def jsonString =（list as JSON）.toString（） 
 
 List parsedList = JSON.parse（jsonString）as List 
 println parsedList [0] .getClass（）// org.codehaus.groovy.grails.web.json.JSONObject 
  

我如何将它解析为Foos？
在此先感谢。

解决方案

我查看了JSON的API文档，可以通过任何方式将JSON字符串解析为特定类型的对象。

因此，您只需自己编写代码即可将每个 JSONObject 为 Foo 。像这样的应该工作：

  import grails.converters.JSON 
 import org.codehaus.groovy.grails.web .json。* 
 
 class Foo {
 def name 
 
 Foo（name）{
 this.name = name 
} 
 
 String toString（）{
 name 
} 
} 
 
 
 List list = [new Foo（first）， new Foo（second）] 
 def jsonString =（list as JSON）.toString（）
 
列表parsedList = JSON.parse（jsonString）
 
 / /从JSONObject列表转换为Foo列表
 def foos = parsedList.collect {JSONObject jsonObject  - > 
 new Foo（name：jsonObject.get（name））
} 
  

更通用的解决方案是向 JSON metaClass添加一个新的静态 parse 方法，如下所示，尝试将JSON字符串解析为特定类型的对象列表：

  import grails.converters.JSON 
 import org.codehaus.groovy.grails.web.json。* 
 
 class Foo {
 def name 
 
 Foo（name）{
 this .name = name 
} 
 
 String toString（）{
 name 
} 
} 
 
 List list = [new Foo（first），new Foo（second）] 
 def jsonString =（列表为JSON）.toString（）
 
 
列表parsedList = JSON.parse jsonString）
 
 //定义新方法
 JSON.metaClass.static.parse = {String json，Class clazz  - > 
 
 List jsonObjs = JSON.parse（json）
 
 jsonObjs.collect {JSONObject jsonObj  - > 
 
 //如果用户没有提供targetClass，请阅读JSON中的'class'proprerty以确定哪种类型转换为
 def targetClass = clazz？：jsonObj.get 'class'）as class 
 def targetInstance = targetClass.newInstance（）
 
 //设置targetInstance 
的属性jsonObj.entrySet（）。each {entry  - > 
 
 if（entry.key！=class）{
 targetInstance。$ entry.key= entry.value 
} 
} 
 targetInstance 
} 
 
} 
 
 //尝试新的分析方法
 List< Foo> foos = JSON.parse（jsonString，Foo）
 
 //确认它有效
断言foos.every {Foo foo  - > foo.class == Foo&& foo.name in ['first'，'second']} 
  

你可以试试上面的代码在常规控制台。几个警告

• 我只对上面的代码进行了非常有限的测试


• JSON类在最新的Grails发行版中，我假设您使用的是不被弃用的类。

I'm converting a list of Foo objects to a JSON string. I need to parse the JSON string back into a list of Foos. However in the following example, parsing gives me a list of JSONObjects instead of Foos.

Example

List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()

List parsedList = JSON.parse(jsonString) as List
println parsedList[0].getClass() // org.codehaus.groovy.grails.web.json.JSONObject

How can I parse it into Foos instead? Thanks in advance.

解决方案

I had a look at the API docs for JSON and there doesn't appear to be any way to parse to a JSON string to a specific type of object.

So you'll just have to write the code yourself to convert each JSONObject to a Foo. Something like this should work:

import grails.converters.JSON
import org.codehaus.groovy.grails.web.json.*

class Foo {
  def name

  Foo(name) {
    this.name = name
  }

  String toString() {
    name
  }
}


List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()

List parsedList = JSON.parse(jsonString)

// Convert from a list of JSONObject to a list of Foo
def foos = parsedList.collect {JSONObject jsonObject ->
    new Foo(name: jsonObject.get("name"))
}

A more general solution would be to add a new static parse method such as the following to the JSON metaClass, that tries to parse the JSON string to a List of objects of a particular type:

import grails.converters.JSON
import org.codehaus.groovy.grails.web.json.*

class Foo {
  def name

  Foo(name) {
    this.name = name
  }

  String toString() {
    name
  }
}

List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()


List parsedList = JSON.parse(jsonString)

// Define the new method
JSON.metaClass.static.parse = {String json, Class clazz ->

    List jsonObjs = JSON.parse(json)

    jsonObjs.collect {JSONObject jsonObj ->

        // If the user hasn't provided a targetClass read the 'class' proprerty in the JSON to figure out which type to convert to
        def targetClass = clazz ?: jsonObj.get('class') as Class
        def targetInstance = targetClass.newInstance()        

        // Set the properties of targetInstance
        jsonObj.entrySet().each {entry ->

            if (entry.key != "class") {
                targetInstance."$entry.key" = entry.value
            }
        }
        targetInstance
    }

}

// Try the new parse method
List<Foo> foos = JSON.parse(jsonString, Foo)

// Confirm it worked
assert foos.every {Foo foo -> foo.class == Foo && foo.name in ['first', 'second'] }

You can try out the code above in the groovy console. A few warnings

• I have only performed very limited testing on the code above
• There are two JSON classes in the latest Grails release, I'm assuming you're using the one that is not deprecated

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