Retrofit2源码解析（二）添加 JacksonConverterFactory转化器

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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> T没有任何限制，什么都可以由jackson处理  @Override  public Converter<ResponseBody, ?> 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  @Override  public Converter<?, RequestBody> 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<HashMap<String, Object>> login(@Body Account body);    }

   @Test    public 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>>() {                    @Override                    public void onResponse(retrofit2.Call<AppRes<User>> call, retrofit2.Response<AppRes<User>> response) {                        System.out.println("onResponse " + response.body().getDes());                    }                    @Override                    public 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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