Retrofit2.0 增加公共参数

有时候，我们会在请求里面加一些公共的参数，比如下面的"device=android"，Retrofit2.0应该怎么做呢？
http://192.168.31.3:90/wallet/info?device=android

我们可以使用Interceptor，Interceptor给我们的印象是可以拦截信息，但它也是可以改造请求然后再发出去。而且Interceptor还可以添加多个呢。

 OkHttpClient.Builder builder = new OkHttpClient.Builder()
.addInterceptor(new ChuckInterceptor(context))
.addInterceptor(loggingInterceptor)
.addInterceptor(httpBaseParamsLoggingInterceptor)
.readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)//设置读取超时时间
.writeTimeout(WRITE_TIMEOUT, TimeUnit.SECONDS)//设置写的超时时间
.connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS);//设置连接超时时间

我们直接封装一个httpBaseParamsLoggingInterceptor，它实现Interceptor的接口就可以了

import android.util.Log;

import com.siluyun.module.common.utils.Utils;

import java.io.EOFException;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.UnsupportedCharsetException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import okhttp3.Connection;
import okhttp3.FormBody;
import okhttp3.Headers;
import okhttp3.HttpUrl;
import okhttp3.Interceptor;
import okhttp3.MediaType;
import okhttp3.Protocol;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import okhttp3.ResponseBody;
import okhttp3.internal.http.HttpHeaders;
import okhttp3.internal.platform.Platform;
import okhttp3.logging.HttpLoggingInterceptor;
import okio.Buffer;
import okio.BufferedSource;

import static okhttp3.internal.platform.Platform.INFO;

public class HttpBaseParamsLoggingInterceptor implements Interceptor {

    Map queryParamsMap = new HashMap<>();
    Map paramsMap = new HashMap<>();
    Map headerParamsMap = new HashMap<>();
    List headerLinesList = new ArrayList<>();

    private HttpBaseParamsLoggingInterceptor() {

    }

    @Override
    public Response intercept(Chain chain) throws IOException {

        Request request = chain.request();
        Request.Builder requestBuilder = request.newBuilder();

        // process header params inject
        Headers.Builder headerBuilder = request.headers().newBuilder();
        if (headerParamsMap.size() > 0) {
            Iterator iterator = headerParamsMap.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry entry = (Map.Entry) iterator.next();
                headerBuilder.add((String) entry.getKey(), (String) entry.getValue());
            }
        }

        if (headerLinesList.size() > 0) {
            for (String line: headerLinesList) {
                headerBuilder.add(line);
            }
        }

        requestBuilder.headers(headerBuilder.build());
        // process header params end




        // process queryParams inject whatever it's GET or POST
        if (queryParamsMap.size() > 0) {
            injectParamsIntoUrl(request, requestBuilder, queryParamsMap);
        }
        // process header params end




        // process post body inject
        if (request.method().equals("POST") && request.body().contentType().subtype().equals("x-www-form-urlencoded")) {
            FormBody.Builder formBodyBuilder = new FormBody.Builder();
            if (paramsMap.size() > 0) {
                Iterator iterator = paramsMap.entrySet().iterator();
                while (iterator.hasNext()) {
                    Map.Entry entry = (Map.Entry) iterator.next();
                    formBodyBuilder.add((String) entry.getKey(), (String) entry.getValue());
                }
            }
            RequestBody formBody = formBodyBuilder.build();
            String postBodyString = bodyToString(request.body());
            postBodyString += ((postBodyString.length() > 0) ? "&" : "") +  bodyToString(formBody);
            requestBuilder.post(RequestBody.create(MediaType.parse("application/x-www-form-urlencoded;charset=UTF-8"), postBodyString));
        } else {    // can't inject into body, then inject into url
            injectParamsIntoUrl(request, requestBuilder, paramsMap);
        }

        request = requestBuilder.build();
        return chain.proceed(request);
    }

    // func to inject params into url
    private void injectParamsIntoUrl(Request request, Request.Builder requestBuilder, Map paramsMap) {
        HttpUrl.Builder httpUrlBuilder = request.url().newBuilder();
        if (paramsMap.size() > 0) {
            Iterator iterator = paramsMap.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry entry = (Map.Entry) iterator.next();
                httpUrlBuilder.addQueryParameter((String) entry.getKey(), (String) entry.getValue());
            }
        }

        requestBuilder.url(httpUrlBuilder.build());
    }

    private static String bodyToString(final RequestBody request){
        try {
            final RequestBody copy = request;
            final Buffer buffer = new Buffer();
            if(copy != null)
                copy.writeTo(buffer);
            else
                return "";
            return buffer.readUtf8();
        }
        catch (final IOException e) {
            return "did not work";
        }
    }

    public static class Builder {

        HttpBaseParamsLoggingInterceptor interceptor;

        public Builder() {
            interceptor = new HttpBaseParamsLoggingInterceptor();
        }

        public Builder addParam(String key, String value) {
            interceptor.paramsMap.put(key, value);
            return this;
        }

        public Builder addParamsMap(Map paramsMap) {
            interceptor.paramsMap.putAll(paramsMap);
            return this;
        }

        public Builder addHeaderParam(String key, String value) {
            interceptor.headerParamsMap.put(key, value);
            return this;
        }

        public Builder addHeaderParamsMap(Map headerParamsMap) {
            interceptor.headerParamsMap.putAll(headerParamsMap);
            return this;
        }

        public Builder addHeaderLine(String headerLine) {
            int index = headerLine.indexOf(":");
            if (index == -1) {
                throw new IllegalArgumentException("Unexpected header: " + headerLine);
            }
            interceptor.headerLinesList.add(headerLine);
            return this;
        }

        public Builder addHeaderLinesList(List headerLinesList) {
            for (String headerLine: headerLinesList) {
                int index = headerLine.indexOf(":");
                if (index == -1) {
                    throw new IllegalArgumentException("Unexpected header: " + headerLine);
                }
                interceptor.headerLinesList.add(headerLine);
            }
            return this;
        }

        public Builder addQueryParam(String key, String value) {
            interceptor.queryParamsMap.put(key, value);
            return this;
        }

        public Builder addQueryParamsMap(Map queryParamsMap) {
            interceptor.queryParamsMap.putAll(queryParamsMap);
            return this;
        }

        public HttpBaseParamsLoggingInterceptor build() {
            return interceptor;
        }

    }
}

怎么使用呢？非常简单：

        HttpBaseParamsLoggingInterceptor httpBaseParamsLoggingInterceptor 
        = new HttpBaseParamsLoggingInterceptor
        .Builder()
        .addParam("device", "android").build();

参考

• Retrofit2.0 公共参数（固定参数）