GSON-KTS

A set of Kotlin extensions for Gson.

一套 Gson 的 Kotlin 扩展库

version:

gradle:

implementation 'com.dhh:gson-ktx:version'

maven:

<dependency>
  <groupId>com.dhh</groupId>
  <artifactId>gson-ktx</artifactId>
  <version>version</version>
  <type>pom</type>
</dependency>

使用方法如下( Sample )

通过 GSON 类访问相关方法：

class GSONTest {

    data class Student(var name: String, var age: Int)

    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
              val xiaoMingJson = """{"name":"XiaoMing","age":22}"""
              val xiaoLiJson = """{"name":"XiaoLi","age":20}"""
              val classJson = """[$xiaoLiJson,$xiaoMingJson]"""
              val studentMapJson = """{"xiaoMing":$xiaoMingJson,"xiaoLi":$xiaoLiJson}"""
              val classMapJson = """{"class1":$classJson,"class2":$classJson}"""


            val xiaoMing: Student = GSON.fromJson<Student>(xiaoMingJson)
            println(xiaoMing)//print -> Student(name=XiaoMing, age=22)

            val xiaoLi: Student = GSON.fromJson<Student>(xiaoLiJson)
            println(xiaoLi)//print -> Student(name=XiaoLi, age=20)
            println(GSON.toJson(xiaoLi))//print -> {"name":"XiaoLi","age":20}

            val list: List<Student> = GSON.fromJson<List<Student>>(classJson)
            println(list)//print -> [Student(name=XiaoLi, age=20), Student(name=XiaoMing, age=22)]

            val studentMap: Map<String, Student> =
                GSON.fromJson<Map<String, Student>>(studentMapJson)
            println(studentMap)//print -> {xiaoMing=Student(name=XiaoMing, age=22), xiaoLi=Student(name=XiaoLi, age=20)}
            println(studentMap["xiaoMing"]?.name)//print -> XiaoMing

            val map: Map<String, List<Student>> = GSON.fromJson<Map<String, List<Student>>>(classMapJson)
            println(map) //print -> {class1=[Student(name=XiaoLi, age=20), Student(name=XiaoMing, age=22)], class2=[Student(name=XiaoLi, age=20), Student(name=XiaoMing, age=22)]}
            
            println(map.toJson())//print -> {"class1":[{"name":"XiaoLi","age":20},{"name":"XiaoMing","age":22}],"class2":[{"name":"XiaoLi","age":20},{"name":"XiaoMing","age":22}]}


        }
    }
}

由于 Kotlin 的类型自动推断功能，可以简写如下：

    val xiaoMing: Student = GSON.fromJson(xiaoMingJson)
    
    val list: List<Student> = GSON.fromJson(classJson)
    
    val studentMap: Map<String, Student> = GSON.fromJson(studentMapJson)
    
    val map: Map<String, List<Student>> = GSON.fromJson(classMapJson)

或者：

    val xiaoMing = GSON.fromJson<Student>(xiaoMingJson)
    
    val list = GSON.fromJson<List<Student>>(classJson)
    
    val studentMap = GSON.fromJson<Map<String, Student>>(studentMapJson)
    
    val map = GSON.fromJson<Map<String, List<Student>>>(classMapJson)

通过 Kotlin 的扩展函数访问：

    val xiaoMingJson = """{name:"XiaoMing",age:22}"""
    
    val student = xiaoMingJson.toBean<Student>()
    val list = classJson.toBean<List<Student>>()

源码非常少，也非常简单，原理就是通过 Kotlin 的内联函数 ( inline ) 和 具体化的类型参数 ( reified ) 特性，将泛型 "T" 通过 TypeToken 获取到 Type 进而进行反序列化。

GSON 源码如下：

object GSON {
    /**
     * 初始化默认的 [com.google.gson.Gson] 转换器
     */
    var gson = GsonBuilder().setLenient().create()

    inline fun <reified T> fromJson(json: String): T {
        val type = object : TypeToken<T>() {}.type
        return gson.fromJson(json, type)
    }

    inline fun <reified T> fromJson(jsonElement: JsonElement): T {
        val type = object : TypeToken<T>() {}.type
        return gson.fromJson(jsonElement, type)
    }

    fun toJson(any: Any) = gson.toJson(any)


    fun toJson(jsonElement: JsonElement) = gson.toJson(jsonElement)

}

扩展函数清单如下：

inline fun <reified T> String.toBean() = GSON.fromJson<T>(this)

inline fun <reified T> JsonElement.toBean() = GSON.fromJson<T>(this)

fun Any.toJson() = GSON.toJson(this)

fun JsonElement.toJson() = GSON.toJson(this)