Gson常用 *** 作

1、获取json某个字段值

不需要先解析成对象，通过JsonElement实现

 try {
            val jumpJson = "{\"iOS\":{\"module\":\"maintenance\",\"action\":\"pushToMaintenance\"},\"android\":{\"module\":\"appointmentMaintai\",\"action\":\"pushToMaintenance\"}}"
            val rootElement = JsonParser.parseString(jumpJson)?.asJsonObject
            val androidElement = rootElement?.get("android")?.asJsonObject
            val module = androidElement?.get("module")?.asString
            val action = androidElement?.get("action")?.asString
            if(!module.isMyBlankOrNull() && !action.isMyBlankOrNull()){
                println("$module $action")
                return
            }
        }catch (e:Exception){

        }

2、json和对象互转

import com.google.gson.Gson
import org.junit.Test
class KTTest {
    data class Person(val name:String,val sex:String,val age:Int)
    @Test
    fun test() {
        //对象转json
        val json = Gson().toJson(Person("皓娇","女",18))
        println(json)
        //json转对象
        val person = Gson().fromJson(json,Person::class.java)
        println(person)
    }

}

 加一个泛型的扩展方法

fun  String.json2Obj(): T {
        val typeT = object : TypeToken(){}.type
        return Gson().fromJson(this, typeT)
    }

这时候你发现是行不通的，报java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to Person，如果想研究其他写法，会更加麻烦，不建议，还是老老实实直接用类转比较好。

3、json和List互转

import com.google.gson.Gson
import com.google.gson.reflect.TypeToken
import org.junit.Test


class KTTest {
    data class Person(val name: String, val sex: String, val age: Int)
    @Test
    fun test() {
        //list转json
        val list = arrayListOf(Person("皓娇1号", "女", 18), Person("皓娇2号", "女", 18))
        val json = Gson().toJson(list)
        println(json)
        //json转list
        val newList = Gson().fromJson>(json, object : TypeToken>() {}.type)
        println(newList)
    }

}

 

4、json转包含泛型的对象

一般网络回调都会包含泛型的方式，方便统一处理。例如：Response{}

class GsonTest2 {
    @Test
    fun test() {
        val resp = BaseResponse(200,Person("皓娇","女",18),"成功")
        val json = Gson().toJson(resp)
        val a = Gson().fromJson>(json,getRespType(Person::class.java))
        println(a)
    }

}

data class Person(val name: String, val sex: String, val age: Int)
data class BaseResponse(val code:Int,val data:T?,val msg:String)

fun getRespType(clz: Class<*>) = object : ParameterizedType {
    override fun getRawType(): Type = BaseResponse::class.java
    override fun getActualTypeArguments(): Array = arrayOf(clz)
    override fun getOwnerType(): Type? = null
}

如果data是List类型，还要在getActualTypeArguments的值上处理，上才艺：

class GsonTest2 {
    @Test
    fun test() {
        val list = arrayListOf(Person("皓娇1号", "女", 18), Person("皓娇2号", "女", 18))
        val resp = BaseResponse(200,list,"成功")
        val json = Gson().toJson(resp)
        val a = Gson().fromJson>>(json,getRespListType(Person::class.java))
        println(a)
    }

}

data class Person(val name: String, val sex: String, val age: Int)
data class BaseResponse(val code:Int,val data:T?,val msg:String)


fun getRespListType(clz: Class<*>) = object : ParameterizedType {
    override fun getRawType(): Type = BaseResponse::class.java
    override fun getActualTypeArguments(): Array = arrayOf(getType(List::class.java, clz))
    override fun getOwnerType(): Type? = null
}