上篇OkHttp3源码(一)——OkHttpClient很荣幸得到评论加关注。
Request —— 是对HTTP请求报文概念的具体实现
请求报文的结构图
根据结构图去阅读源码能很好的理解某些属性的真实意义。
我们看一下源码。
public final class Request {
final HttpUrl url;
final String method;
final Headers headers;
final RequestBody body;
final Object tag;
private volatile CacheControl cacheControl; // Lazily initialized.
Request(Builder builder) {
this.url = builder.url;
this.method = builder.method;
this.headers = builder.headers.build();
this.body = builder.body;
this.tag = builder.tag != null ? builder.tag : this;
}
//返回设置的URL
public HttpUrl url() {
return url;
}
//返回设置的方法 get或post
public String method() {
return method;
}
//返回所有的头部对象(这里的对象可以理解为一个键值对)
public Headers headers() {
return headers;
}
//返回头部名称为name的信息
public String header(String name) {
return headers.get(name);
}
//返回头部所有名称为name的信息
public List<String> headers(String name) {
return headers.values(name);
}
//返回请求体
public RequestBody body() {
return body;
}
//返回设置的请求标签
public Object tag() {
return tag;
}
//根据自身设置的参数重新构造对象
public Builder newBuilder() {
return new Builder(this);
}
//根据在头部设置的与缓存有关的信息,返回缓存控制器,
public CacheControl cacheControl() {
CacheControl result = cacheControl;
return result != null ? result : (cacheControl = CacheControl.parse(headers));
}
//是否用的HTTPS协议
public boolean isHttps() {
return url.isHttps();
}
/**
* 接下来就是Builder设计模式
* OkHttp用的比较多的设计模式
* 对Builder模式不了解的,先去了解下。这里概括一下Builder模式:类的某些字段无法通过自身去赋值,需要委托给其他类去赋值。
*/
public static class Builder {
HttpUrl url;
String method;
Headers.Builder headers;
RequestBody body;
Object tag;
//由这里可以看出Request的默认请求方式是“GET”,且header为空
public Builder() {
this.method = "GET";
this.headers = new Headers.Builder();
}
//根据Resquest已设置的参数重新创建对象
Builder(Request request) {
this.url = request.url;
this.method = request.method;
this.body = request.body;
this.tag = request.tag;
this.headers = request.headers.newBuilder();
}
//设置HttpUrl,这里就省去了对String url 内容的封装。
public Builder url(HttpUrl url) {
if (url == null) throw new NullPointerException("url == null");
this.url = url;
return this;
}
//设置url, 这里需要对String url的内容封装成HttpUrl。
public Builder url(String url) {
if (url == null) throw new NullPointerException("url == null");
// Silently replace web socket URLs with HTTP URLs.
if (url.regionMatches(true, 0, "ws:", 0, 3)) {
url = "http:" + url.substring(3);
} else if (url.regionMatches(true, 0, "wss:", 0, 4)) {
url = "https:" + url.substring(4);
}
HttpUrl parsed = HttpUrl.parse(url);
if (parsed == null) throw new IllegalArgumentException("unexpected url: " + url);
return url(parsed);
}
//设置URL,其实内部的实现与String url相同。
public Builder url(URL url) {
if (url == null) throw new NullPointerException("url == null");
HttpUrl parsed = HttpUrl.get(url);
if (parsed == null) throw new IllegalArgumentException("unexpected url: " + url);
return url(parsed);
}
//设置一个头部信息(键值对的形式),并将与此name相同的头部信息全部清除。
public Builder header(String name, String value) {
headers.set(name, value);
return this;
}
//添加一个头部信息(键值对的形式),这里这是不用清除其他头部信息
public Builder addHeader(String name, String value) {
headers.add(name, value);
return this;
}
//清除所有头部名称为name的信息
public Builder removeHeader(String name) {
headers.removeAll(name);
return this;
}
//设置头部对象
public Builder headers(Headers headers) {
this.headers = headers.newBuilder();
return this;
}
//设置将缓存控制器里面设置的信息添加到头部
public Builder cacheControl(CacheControl cacheControl) {
String value = cacheControl.toString();
if (value.isEmpty()) return removeHeader("Cache-Control");
return header("Cache-Control", value);
}
//设置get方法并且请求体为null
public Builder get() {
return method("GET", null);
}
//设置post方法并且请求体不能为null
public Builder post(RequestBody body) {
return method("POST", body);
}
//设置方法,如果方法有请求体,必须设置请求体
public Builder method(String method, RequestBody body) {
if (method == null) throw new NullPointerException("method == null");
if (method.length() == 0) throw new IllegalArgumentException("method.length() == 0");
if (body != null && !HttpMethod.permitsRequestBody(method)) {
throw new IllegalArgumentException("method " + method + " must not have a request body.");
}
if (body == null && HttpMethod.requiresRequestBody(method)) {
throw new IllegalArgumentException("method " + method + " must have a request body.");
}
this.method = method;
this.body = body;
return this;
}
//设置当前请求体的标签
public Builder tag(Object tag) {
this.tag = tag;
return this;
}
//创建Request对象。
public Request build() {
if (url == null) throw new IllegalStateException("url == null");
return new Request(this);
}
}
}
通过上面的注释分析我们知道:
Request类主要配置网络请求的请求体,
相关参数有HttpUrl、method、Headers、RequestBody、CacheControl。
对于除method以外的其他参数类,都是对网络请求的请求体相关信息的封装。
我们后面会解释Headers、RequestBody、CacheControl三个类。