一、概述

Android(Java) 平台已经有许多 Json 库了，包括 Google 推荐的 Gson，广受欢迎的 Jackson，阿里的 FastJson 等，但今天要说的是大名鼎鼎 Square 公司的 MoShi 。
轮子已经有很多了，不过自从 Google 将 Kotlin 定为 Android 亲儿子开发语言后，竟然包括 Gson 在内的几乎所有 Json 库均不支持，这当然可以理解，因为他们大多数采用了 Java 反射机制，注定难以适配 Kotlin 独有的特性。因此今天要介绍 Moshi —— 一个与 Kotlin 兼容极好的现代化解析库。可以很好的兼容 java 和 Kotlin。

二、java中使用

导入

  1.  implementation 'com.squareup.moshi:moshi:1.12.0'

Bean类

  1. public class JavaBean {
  2.     private String name;
  3.     private String sex;
  4.     private int age;
  6.     public JavaBean(String name, String sex, int age) {
  7.         this.name = name;
  8.         this.sex = sex;
  9.         this.age = age;
  10.     }
  12.     public String getName() {
  13.         return name;
  14.     }
  16.     public void setName(String name) {
  17.         this.name = name;
  18.     }
  20.     public String getSex() {
  21.         return sex;
  22.     }
  24.     public void setSex(String sex) {
  25.         this.sex = sex;
  26.     }
  28.     public int getAge() {
  29.         return age;
  30.     }
  32.     public void setAge(int age) {
  33.         this.age = age;
  34.     }
  36.     @Override
  37.     public String toString() {
  38.         return "JavaBean{" +
  39.                 "name='" + name + '\'' +
  40.                 ", sex='" + sex + '\'' +
  41.                 ", age=" + age +
  42.                 '}';
  43.     }
  44. }

Bean

  • json -> bean

    1. private static void json2Bean() {
    2.   String jj = "{\"age\":22,\"name\":\"alice\",\"sex\":\"man\"}";
    3.   JsonAdapter<JavaBean> adapter = new Moshi.Builder().build().adapter(JavaBean.class);
    4.   try {
    5.       JavaBean bean = adapter.fromJson(jj);
    6.       System.out.println(bean);
    7.   } catch (IOException e) {
    8.       e.printStackTrace();
    9.   }
    10. }

  • bean -> json

    1. private static void bean2Json() {
    2.   JavaBean javaBean = new JavaBean("alice", "man", 22);
    3.   JsonAdapter<JavaBean> adapter = new Moshi.Builder().build().adapter(JavaBean.class);
    4.   String json = adapter.toJson(javaBean);
    5.   System.out.println(json);
    6. }

    Map

  • map -> json

    1. private static void map2Json() {
    2.   Map<String, Integer> map = new HashMap<>();
    3.   map.put("one", 1);
    4.   map.put("two", 2);
    5.   map.put("three", 3);
    6.   Moshi moshi = new Moshi.Builder().build();
    7.   ParameterizedType type = Types.newParameterizedType(Map.class, String.class, Integer.class);
    8.   JsonAdapter<Object> adapter = moshi.adapter(type);
    9.   String json = adapter.toJson(map);
    10.   System.out.println(json);
    11. }

  • json -> map

    1. private static void json2Map() {
    2.   String json = "{\"one\":1,\"two\":2,\"three\":3}";
    3.   Moshi moshi = new Moshi.Builder().build();
    4.   ParameterizedType type = Types.newParameterizedType(Map.class, String.class, Integer.class);
    5.   JsonAdapter<Map<String, Integer>> adapter = moshi.adapter(type);
    6.   try {
    7.       Map<String, Integer> map = adapter.fromJson(json);
    8.       System.out.println(map);
    9.   } catch (IOException e) {
    10.       e.printStackTrace();
    11.   }
    12. }

    List

  • list -> json

    1. private static void list2Json() {
    2.   ArrayList<JavaBean> list = new ArrayList<>();
    3.   for (int i = 0; i < 3; i++) {
    4.       list.add(new JavaBean("alice" + i, "man" + i, 23 + i));
    5.   }
    6.   Type listOfCardsType = Types.newParameterizedType(List.class, JavaBean.class);
    7.   JsonAdapter<Object> adapter = new Moshi.Builder().build().adapter(listOfCardsType);
    8.   String json = adapter.toJson(list);
    9.   System.out.println(json);
    10. }

  • json -> list

    1. private static void json2list() {
    2.   String json = "[{\"age\":23,\"name\":\"alice0\",\"sex\":\"man0\"},{\"age\":24,\"name\":\"alice1\",\"sex\":\"man1\"},{\"age\":25,\"name\":\"alice2\",\"sex\":\"man2\"}]";
    3.   Type listOfCardsType = Types.newParameterizedType(List.class, JavaBean.class);
    4.   JsonAdapter<List<JavaBean>> adapter = new Moshi.Builder().build().adapter(listOfCardsType);
    5.   try {
    6.       List<JavaBean> list = adapter.fromJson(json);
    7.       System.out.println(list);
    8.   } catch (IOException e) {
    9.       e.printStackTrace();
    10.   }
    11. }

    Others

  • @json：Key转换

  • transitent：跳过该字段不解析
  1. public final class Bean {
  2.   @Json(name = "lucky number") int luckyNumber;
  3.   @Json(name = "objec") int data;
  4.   @Json(name = "toatl_price") String totolPrice;
  5.   private transient int total;//jump the field
  6. }

三、Kotlin中使用

这里有两种，第一种是用反射的方式，不过这种方式有两个缺点，一是引入的包有点大，两一个就是对性能有影响。所以这里用注解的方式。
引入kapt:

  1. kapt 'com.squareup.moshi:moshi-kotlin-codegen:1.12.0'

Bean类

  1. @JsonClass(generateAdapter = true)
  2. data class KotlinBean(var name: String, var age: Int)

或者下面这种：

  1. @JsonClass(generateAdapter = true)
  2. data class TestCode(
  3.     @Json(name = "age")
  4.     var age: Int,
  5.     @Json(name = "name")
  6.     var name: String
  7. ){
  8.     fun isDTwty() = age > 20
  9. }

Bean

  1. @OptIn(ExperimentalStdlibApi::class)
  2. fun json2Bean() {
  3.     val jsont = "{\"name\":\"alice\",\"age\":33}"
  4.     val adapter = Moshi.Builder().build().adapter<KotlinBean>()
  5.     println(adapter.fromJson(jsont))
  6. }
  8. @SuppressLint("CheckResult")
  9. @OptIn(ExperimentalStdlibApi::class)
  10. private fun bean2Json() {
  11.     val adapter = Moshi.Builder().build().adapter<KotlinBean>()
  12.     println(adapter.toJson(KotlinBean("alice", 33)))
  13. }

Map

  1. fun json2Map() {
  2.     val json = "{\"name\":\"hello\",\"age\":99}"
  3.     val types = Types.newParameterizedType(Map::class.java, String::class.java,Any::class.java)
  4.     val adapter = Moshi.Builder().build().adapter<Map<String,Any>>(types)
  5.     val map = adapter.fromJson(json)
  6.     println(map?.get("name"))
  7. }
  9. fun map2Json() {
  10.     val map = mapOf("name" to "hello","age" to 99)
  11.     val types = Types.newParameterizedType(Map::class.java, String::class.java,Any::class.java)
  12.     val adapter = Moshi.Builder().build().adapter<Map<String,Any>>(types)
  13.     val json = adapter.toJson(map)
  14.     println(json)
  15. }

List

  1. fun json2List() {
  2.     println("-------------")
  3.     val json = "[{\"name\":\"alice\",\"age\":22},{\"name\":\"bob\",\"age\":12}]"
  4.     val type = Types.newParameterizedType(List::class.java,KotlinBean::class.java)
  5.     val adapter = Moshi.Builder().build().adapter<List<KotlinBean>>(type)
  6.     val list = adapter.fromJson(json)
  7.     list?.forEach { println(it) }
  8. }
  10. fun list2Json() {
  11.     val list = listOf(KotlinBean("alice",22),KotlinBean("bob",12))
  12.     val type = Types.newParameterizedType(List::class.java,KotlinBean::class.java)
  13.     val adapter = Moshi.Builder().build().adapter<List<KotlinBean>>(type)
  14.     val json = adapter.toJson(list)
  15.     println(json)
  16. }

Custom Type Adapters

  1. @JsonClass(generateAdapter = true)
  2. data class PersonAd(var name: String?, var age: Int,var sexAd: SexAd)
  4. enum class SexAd{
  5.     MAN,WOMAN;
  6. }
  8. class SexAdapter{
  9.     @FromJson
  10.     fun fromJson(value: Int): SexAd{
  11.         return if (value == 0) SexAd.MAN else SexAd.WOMAN
  12.     }
  13.     @ToJson
  14.     fun toJson(sexAd: SexAd): Int{
  15.        return if (sexAd == SexAd.MAN) 0 else 1
  16.     }
  17. }
  19. class CommonAdapter{
  20.     @FromJson
  21.     fun fromJson(value: String?): String{
  22.         //如果json数据没有这个字段，不执行这里
  23.         println("fromJson--$value")
  24.         return if (value.isNullOrEmpty()) "这是空" else value
  25.     }
  26.     @ToJson
  27.     fun toJson(value: String?): String{
  28.        return if (value.isNullOrEmpty()) "this is null" else value
  29.     }
  30. }
  32. @ExperimentalStdlibApi
  33. fun main() {
  34. //测试SexAdapter
  35. /*    val personAd = PersonAd("alice",99,SexAd.MAN)
  36.     val moshi = Moshi.Builder().add(SexAdapter()).build()
  37.     val adapter = moshi.adapter<PersonAd>()
  38.     val json = adapter.toJson(personAd)
  39.     println(json)
  40.     val jj = "{\"name\":\"alice\",\"age\":99,\"sexAd\":1}"
  41.     println("------${GsonKtx.toJson(personAd)}")
  42.     val fromJson = adapter.fromJson(jj)
  43.     println(fromJson)*/
  44.     println("---------------")
  45.       //测试通用CommonAdapter
  46.     val personAd = PersonAd("",99,SexAd.MAN)
  47.     val moshi = Moshi.Builder()
  48.         .add(CommonAdapter())
  49. //        .add(SexAdapter())
  50.         .build()
  51.     val adapter = moshi.adapter<PersonAd>()
  52.     val json = adapter.toJson(personAd)
  53.     println(json)
  54.     val jj = "{\"name\":null,\"age\":99,\"sexAd\":\"MAN\"}"
  55.     val person = adapter.fromJson(jj)
  56.     println(person)
  58. }

Codegen

使用codegen会自动生成adpter,可以直接使用。导入kapt依赖，在bean类上加上@JsonClass(generateAdapter = true)，示例如下： 

  1. @JsonClass(generateAdapter = true)
  2. data class TestCode(
  3.     @Json(name = "age")
  4.     var age: Int,
  5.     @Json(name = "name")
  6.     var name: String
  7. ){
  8.     fun isDTwty() = age > 20
  9. }

序列化和反序列化：

  1. val bean = TestCode(9,"moshi")
  2.  println(TestCodeJsonAdapter(Moshi.Builder().build()).fromJson("{\"age\":9,\"name\":\"moshi\"}"))
  3.  println(TestCodeJsonAdapter(Moshi.Builder().build()).toJson(bean))

四、封装代码

  1. object MSKtx {
  2.     val moshi: Moshi = Moshi.Builder().build()
  4.     @OptIn(ExperimentalStdlibApi::class)
  5.     inline fun <reified T> toJson(t: T?): String? {
  6.         if (t == null) return null
  7.         return moshi.adapter<T>().toJson(t)
  8.     }
  10.     fun <T> fromJson(json: String?, type: Type): T? {
  11.         if (json.isNullOrEmpty()) {
  12.             return null
  13.         }
  14.         val adapter = moshi.adapter<T>(type)
  15.         return adapter.fromJson(json)
  16.     }
  19.     @OptIn(ExperimentalStdlibApi::class)
  20.     inline fun <reified T> toAny(json: String?): T? {
  21.         if (json.isNullOrEmpty()) {
  22.             return null
  23.         }
  24.         val adapter = moshi.adapter<T>()
  25.         return adapter.fromJson(json)
  26.     }
  28.     inline fun <reified K, reified V> toMap(json: String?): MutableMap<K, V>? =
  29.         fromJson(json, Types.newParameterizedType(Map::class.java, K::class.java, V::class.java))
  31.     inline fun <reified T> toList(json: String?): MutableList<T>? =
  32.         fromJson(json, Types.newParameterizedType(MutableList::class.java, T::class.java))
  33. }
  35. fun Any?.toJson() = MSKtx.toJson(this)
  37. fun <T> String?.fromJson(type: Type) = MSKtx.fromJson<T>(this, type)
  39. inline fun <reified T> String?.toAny() = MSKtx.toAny<T>(this)
  41. inline fun <reified K, reified V> String?.toMap() = MSKtx.toMap<K, V>(this)
  43. inline fun <reified T> String?.toList() = MSKtx.toList<T>(this)

使用示例：

java

  1. private static void skTest() {
  2.     JavaBean javaBean = new JavaBean("alice", "man", 22);
  3.     System.out.println(MSKtxKt.toJson(javaBean));
  5.     String jj = "{\"age\":22,\"name\":\"alice\",\"sex\":\"man\"}";
  6.     JavaBean bean = MSKtxKt.fromJson(jj, Types.newParameterizedType(JavaBean.class));
  7.     System.out.println(bean);
  8. }

Kotlin

  1. println(MSKtx.toAny<TestCode>("{\"age\":9,\"name\":\"moshi\"}"))
  2. /*println(MSKtx.toJson(KotlinBean("alice", 33)))
  3. println(MSKtx.toJson(mapOf("name" to "hello","age" to 99)))
  4. println(MSKtx.toJson(listOf(KotlinBean("alice",22),KotlinBean("bob",12))))
  5. println("-------------")
  6. println(MSKtx.toAny<KotlinBean>("{\"name\":\"alice\",\"age\":33}"))
  7. println(MSKtx.toMap<String, Any>("{\"name\":\"hello\",\"age\":99}"))
  8. println(MSKtx.toList<KotlinBean>("[{\"name\":\"alice\",\"age\":22},{\"name\":\"bob\",\"age\":12}]"))*/

五、参考

新一代Json解析库Moshi使用及原理解析

Moshi with Kotlin Json 库—现代化的最佳损友