Android：使用Gson常见问题（包含解决将Long型转化为科学计数法的问题）

一、解决将Long型转化为科学计数法的问题

1.1 场景

将一个对象转为Map类型时，调用Gson.fromJson发现，原来对象中的long类型的personId字段，被解析成了科学计数法，导致请求接口失败，报参数错误。

解决结果图

1.2、ExampleUnitTest.kt示例代码

data class ReuestParmObj(val personId: Long = 1668394335647, val personType: Int = 1)
class ExampleUnitTest {private val mGson: Gson = Gson()@Testfun gsonReuestParmJson() {val reuestParmObj = ReuestParmObj(1668394335647, 1)val reuestParmJson: String = mGson.toJson(reuestParmObj)println("reuestParmJson信息：$reuestParmJson")val mapParm: Map<String, *> =mGson.fromJson(reuestParmJson, Map::class.java) as Map<String, *>println("mapParms信息：$mapParm")}
}

测试结果

1.3 解决将Long型转化为科学计数法问题的方案

修改gson配置
private val mGson: Gson = GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).create()

data class ReuestParmObj(val personId: Long = 1668394335647, val personType: Int = 1)
class ExampleUnitTest {
//    private val mGson: Gson = Gson()private val mGson: Gson = GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).create()@Testfun gsonReuestParmJson() {val reuestParmObj = ReuestParmObj(1668394335647, 1)val reuestParmJson: String = mGson.toJson(reuestParmObj)println("reuestParmJson信息：$reuestParmJson")val mapParm: Map<String, *> =mGson.fromJson(reuestParmJson, Map::class.java) as Map<String, *>println("mapParms信息：$mapParm")}
}

测试结果

二、 把null值也转换，默认是不转换null值的

设置：serializeNulls()

 private val mGson: Gson = GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).serializeNulls().create()

三、Html的转换

Gson默认是把Html 转义的，但也可以设置不转义。
设置：disableHtmlEscaping()

class ExampleUnitTest {@Testfun testDisableHtmlEscaping(){val gson1: Gson = Gson()val gson2: Gson = GsonBuilder().disableHtmlEscaping().create()val htmlStr = "<h3>测试disableHtmlEscaping</h3>"println("未设置disableHtmlEscaping转换htmlStr结果：${gson1.toJson(htmlStr)}")println("设置disableHtmlEscaping转换htmlStr结果：${gson2.toJson(htmlStr)}")}
}

测试结果

四、设置输入json格式

默认的输出是compact格式，示例
{"personId":1668394335647,"personType":1}
设置：setPrettyPrinting（）

class ExampleUnitTest {@Testfun testSetPrettyPrinting(){val gson1: Gson = Gson()val gson2: Gson = GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).setPrettyPrinting().create()val reuestParmObj = ReuestParmObj(1668394335647, 1)println("未设置 setPrettyPrinting 转换reuestParmObj结果：${gson1.toJson(reuestParmObj)}")println("设置 setPrettyPrinting 转换reuestParmObj结果：${gson2.toJson(reuestParmObj)}")}
}

测试结果

五、ExampleUnitTest.kt文件完整代码

import com.google.gson.Gson
import com.google.gson.GsonBuilder
import com.google.gson.LongSerializationPolicy
import com.google.gson.reflect.TypeToken
import org.junit.Test/*** Example local unit test, which will execute on the development machine (host).** See [testing documentation](http://d.android.com/tools/testing).*/data class ReuestParmObj(val personId: Long = 1668394335647, val personType: Int = 1)
class ExampleUnitTest {private val mGson1: Gson = Gson()private val mGson2: Gson =GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).serializeNulls().disableHtmlEscaping().create()@Testfun gsonReuestParmJson() {val reuestParmObj = ReuestParmObj(1668394335647, 1)val reuestParmJson1: String = mGson1.toJson(reuestParmObj)val reuestParmJson2: String = mGson2.toJson(reuestParmObj)println("reuestParmJson1 信息：$reuestParmJson1")println("reuestParmJson2 信息：$reuestParmJson2")//        val type = object : TypeToken<Map<String, *>>() {}.type
//        val mapParm: Map<String, *> = mGson1.fromJson(reuestParmJson, type)val mapParm1: Map<String, *> =mGson1.fromJson(reuestParmJson1, Map::class.java) as Map<String, *>println("mapParm1 信息：$mapParm1")val mapParm2: Map<String, *> =mGson2.fromJson(reuestParmJson2, Map::class.java) as Map<String, *>println("mapParms2 信息：$mapParm2")/*reuestParmJson1 信息：{"personId":1668394335647,"personType":1}reuestParmJson2 信息：{"personId":"1668394335647","personType":1}mapParm1 信息：{personId=1.668394335647E12, personType=1.0}mapParms2 信息：{personId=1668394335647, personType=1.0}*/}@Testfun testDisableHtmlEscaping() {val gson1: Gson = Gson()val gson2: Gson = GsonBuilder().disableHtmlEscaping().create()val htmlStr = "<h3>测试disableHtmlEscaping</h3>"println("未设置disableHtmlEscaping转换htmlStr结果：${gson1.toJson(htmlStr)}")println("设置disableHtmlEscaping转换htmlStr结果：${gson2.toJson(htmlStr)}")/*未设置disableHtmlEscaping转换htmlStr结果："\u003ch3\u003e测试disableHtmlEscaping\u003c/h3\u003e"设置disableHtmlEscaping转换htmlStr结果："<h3>测试disableHtmlEscaping</h3>"*/}@Testfun testSetPrettyPrinting() {val gson1: Gson = Gson()val gson2: Gson = GsonBuilder().setLongSerializationPolicy(LongSerializationPolicy.STRING).setPrettyPrinting().create()val reuestParmObj = ReuestParmObj(1668394335647, 1)println("未设置 setPrettyPrinting 转换reuestParmObj结果：${gson1.toJson(reuestParmObj)}")println("设置 setPrettyPrinting 转换reuestParmObj结果：${gson2.toJson(reuestParmObj)}")/*未设置 setPrettyPrinting 转换reuestParmObj结果：{"personId":1668394335647,"personType":1}设置 setPrettyPrinting 转换reuestParmObj结果：{"personId": "1668394335647","personType": 1}*/}
}