retrofit是个强大的工具,而retrofit converter可以把请求的结果转为可供我们直接使用的java bean对象。如果不使用转换工厂retrofit则请求方法回只能为ResponseBody对象。
官方为我们提供了一些默认的转换工厂:https://github.com/square/retrofit/tree/master/retrofit-converters
public interface GitHubService {
@GET("users/{user}")
Call getUserInfo(@Path("user") String user);
}
要使用工厂就要在retrofit实例设置转换工厂:
Retrofit retrofit = new Retrofit.Builder()
.addConverterFactory(GsonConverterFactory.create())
.build();
这里设置了一个GsonConverterFactory,它可以把http请求响应json数据转为java bean;这里json数据被反序列化为User
对象了;但是这个retrofit对象就只能处理gson数据了;
一般服务器接口所返回的数据结构都是统一规范的,比如返回数据结构为JSON;那如果有特殊情况怎么办?比如服务中有个接口返回xml数据,上面的retrofit实例就不能用了,只能从新创建了;
自定义一个可以混用的转换工厂,它自己并不处理数据,给它设置默认工厂来处理数据,比如GsonConverterFactory就处理json数据,设置SimpleXmlConverterFactory就处理xml数据;并且还可以在请求方法上设置注解
来动态设置转换工厂;
CompositeConverterFactory.java
public class CompositeConverterFactory extends Converter.Factory {
private Converter.Factory mFactory;
public static CompositeConverterFactory create(Converter.Factory factory) {
if (factory == null) {
throw new NullPointerException("parameter is null");
} else {
return new CompositeConverterFactory(factory);
}
}
private CompositeConverterFactory(Converter.Factory factory) {
this.mFactory = factory;
}
@Override
public Converter responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
Class> factoryClass = null;
for (Annotation annotation : annotations) {
if (annotation instanceof ResponseConverter) {
factoryClass = ((ResponseConverter) annotation).value();
break;
}
}
Converter.Factory factory = null;
if (factoryClass != null) {
try {
Method createMethod = factoryClass.getMethod("create");
factory = (Converter.Factory) createMethod.invoke(null);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
if (factory == null && mFactory != null) {
factory = mFactory;
}
if (factory != null)
return factory.responseBodyConverter(type, annotations, retrofit);
return super.responseBodyConverter(type, annotations, retrofit);
}
@Override
public Converter, RequestBody> requestBodyConverter(Type type, Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
Class> factoryClass = null;
for (Annotation paramAnno : methodAnnotations) {
if (paramAnno instanceof RequestConverter) {
factoryClass = ((RequestConverter) paramAnno).value();
break;
}
}
Converter.Factory factory = null;
if (factoryClass != null) {
try {
Method createMethod = factoryClass.getMethod("create");
factory = (Converter.Factory) createMethod.invoke(null);
return factory.requestBodyConverter(type, parameterAnnotations, methodAnnotations, retrofit);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
if (factory == null && mFactory != null) {
factory = mFactory;
}
if (factory != null)
return factory.requestBodyConverter(type, parameterAnnotations, methodAnnotations, retrofit);
return super.requestBodyConverter(type, parameterAnnotations, methodAnnotations, retrofit);
}
}
@RequestConverter
@Documented
@Target({METHOD})
@Retention(RUNTIME)
public @interface RequestConverter {
Class extends Converter.Factory> value();
}
@ResponseConverter
@Documented
@Target({METHOD})
@Retention(RUNTIME)
public @interface ResponseConverter {
Class extends Converter.Factory> value();
}
使用自定义转换工厂:
Retrofit retrofit = new Retrofit.Builder()
.addConverterFactory(CompositeConverterFactory.create(GsonConverterFactory.create()))
.build();
这里默认设置GsonConverterFactory,默认处理json数据结构的数据。CompositeConverterFactory转换什么数据由传入的默认工厂决定。
CompositeConverterFactory.create(factory)
传入参数为默认工厂;
public interface GitHubService {
@ResponseConverter(GsonConverterFactory.class)
@GET("users/{user}")
Call getUserInfo(@Path("user") String user);
}
@ResponseConverter(ScalarsConverterFactory.class)
@GET("users/{user}")
Call getUserInfo2(@Path("user") String user);
@RequestConverter(GsonConverterFactory.class)
@POST("/uploaddata")
Call upload(@Body User user);
是不是很简单?It is easy!!!
repositories {
jcenter()
}
dependencies {
implementation 'com.github.woodyhi.retrofit:composite-converter:0.1.3'
}
PS:源码 https://github.com/woodyhi/retrofit-converter 其中有test代码来演示。