Retrofit2源码解析（二）添加 JacksonConverterFactory转化器

1、获取实例时，我们添加个转化器

        retrofit = new Retrofit.Builder().baseUrl("http://localhost:8080/campus/").addConverterFactory(JacksonConverterFactory.create()).build();

这时候相当于就多了一个转化器。所以还是支持上篇中的请求方式（主要是返回类型和入参类型）

2、话不多话。直接看转化器源码，看它支持哪些类型

retrofit2.converter.jackson.JacksonConverterFactory.javapublic final class JacksonConverterFactory extends Converter.Factory {public static JacksonConverterFactory create() {return create(new ObjectMapper());}public static JacksonConverterFactory create(ObjectMapper mapper) {return new JacksonConverterFactory(mapper);}private final ObjectMapper mapper;private JacksonConverterFactory(ObjectMapper mapper) {if (mapper == null) throw new NullPointerException("mapper == null");this.mapper = mapper;}
//返回类型retrofit2.Call T没有任何限制，什么都可以由jackson处理@Overridepublic Converter responseBodyConverter(Type type, Annotation[] annotations,Retrofit retrofit) {JavaType javaType = mapper.getTypeFactory().constructType(type);ObjectReader reader = mapper.reader(javaType);return new JacksonResponseBodyConverter<>(reader);}//接口的形参类型也没有任何限制，什么都可以由jackson处理@Overridepublic Converter requestBodyConverter(Type type,Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {JavaType javaType = mapper.getTypeFactory().constructType(type);ObjectWriter writer = mapper.writerWithType(javaType);return new JacksonRequestBodyConverter<>(writer);}
}

是不是很爽。我们试下，在第一篇的基础对请求接口做修改

    public interface HttpLogin {@POST("account/login")//直接返回一个HashMap看看retrofit2.Call> login(@Body Account body);}

   @Testpublic void testRetrofit() {retrofit2.Call<HashMap<String, Object>> login = retrofit.create(HttpLogin.class).login(new Account("yincs", null));login.enqueue(new retrofit2.Callback<HashMap<String, Object>>() {public void onResponse(retrofit2.Call<HashMap<String, Object>> call,retrofit2.Response<HashMap<String, Object>> response) {System.out.println("onResponse " + response.body().get("des"));}public void onFailure(retrofit2.Call<HashMap<String, Object>> call, Throwable t) {System.out.println("onFailure " + t.getMessage());}});sleep(12000);}执行结果
onResponse 参数错误[密码不能为空]
Process finished with exit code 0也是成功的 

一般服务器返回的参数形式一样。那我们能不能用一个统一类加泛型处理呢？
答案是当然可以的
先创建一个统一类

public class AppRes<T> {private int code;private String des;T data;public int getCode() {return code;}public void setCode(int code) {this.code = code;}public String getDes() {return des;}public void setDes(String des) {this.des = des;}public T getData() {return data;}public void setData(T data) {this.data = data;}
}

接口改下

     public interface HttpLogin {@POST("account/login")retrofit2.Call<AppRes<User>> login(@Body Account body);}

执行下

        retrofit.create(HttpLogin.class).login(new Account("ycs",null)).enqueue(new retrofit2.Callback<AppRes<User>>() {@Overridepublic void onResponse(retrofit2.Call<AppRes<User>> call, retrofit2.Response<AppRes<User>> response) {System.out.println("onResponse " + response.body().getDes());}@Overridepublic void onFailure(retrofit2.Call<AppRes<User>> call, Throwable t) {System.out.println("onFailure " + t.getMessage());}});
返回结果
onResponse 参数错误[密码不能为空]Process finished with exit code 0

一切ok!!!

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