xUtils3源码阅读之网络模块

Posted 一口仨馍

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关于xUtils3

  • xUtils 包含了很多实用的android工具.
  • xUtils 支持超大文件(超过2G)上传,更全面的http请求协议支持(11种谓词),拥有更加灵活的ORM,更多的事件注解支持且不受混淆影响…
  • xUtils 最低兼容Android 4.0 (api level 14). (Android 2.3?)
  • xUtils3变化较多所以建立了新的项目不在旧版(github.com/wyouflf/xUtils)上继续维护, 相对于旧版本:
    1. HTTP实现替换HttpClient为UrlConnection, 自动解析回调泛型, 更安全的断点续传策略.
    2. 支持标准的Cookie策略, 区分domain, path…
    3. 事件注解去除不常用的功能, 提高性能.
    4. 数据库api简化提高性能, 达到和greenDao一致的性能.
    5. 图片绑定支持gif(受系统兼容性影响, 部分gif文件只能静态显示), webp; 支持圆角, 圆形, 方形等裁剪, 支持自动旋转…

xUtils3四大模块:网络请求、图片加载、ORM框架和事件注解。本文阅读分析网络请求相关代码。

使用版本:compile ‘org.xutils:xutils:3.3.36‘

xUtils3项目地址 : https://github.com/wyouflf/xUtils3

初始化

Ext.init(this);

    public static class Ext {
        private static Application app;
        public static void init(Application app) {
            if (Ext.app == null) {
                Ext.app = app;
            }
        }
    }

获取ApplicationCotext,方便以后调用。在Ext中有个静态代码块。详情如下:

    public static class Ext {
        private static TaskController taskController;
        static {
            TaskControllerImpl.registerInstance();
            // 默认信任所有https域名
            HttpsURLConnection.setDefaultHostnameVerifier(new HostnameVerifier() {
                @Override
                public boolean verify(String hostname, SSLSession session) {
                    return true;
                }
            });
        } 

        public static void setTaskController(TaskController taskController) {
            if (Ext.taskController == null) {
                Ext.taskController = taskController;
            }
        }
    }
    public static void registerInstance() {
        if (instance == null) {
            synchronized (TaskController.class) {
                if (instance == null) {
                    instance = new TaskControllerImpl();
                }
            }
        }
        x.Ext.setTaskController(instance);
    } 

这段静态代码块的作用是注册TaskController对象为TaskControllerImpl实例。并设置信任所有https域名。ps:还是中文注释看着爽。

添加参数

RequestParams param = new RequestParams(url);
param.addParameter("name","一口仨馍");
    public RequestParams(String uri) {
        this(uri, null, null, null);
    }

    public RequestParams(String uri, ParamsBuilder builder, String[] signs, String[] cacheKeys) {
        if (uri != null && builder == null) {
            builder = new DefaultParamsBuilder();
        }
        this.uri = uri;
        this.signs = signs;
        this.cacheKeys = cacheKeys;
        this.builder = builder;
    }

    public void addParameter(String name, Object value) {
        if (value == null) return;

        if (method == null || HttpMethod.permitsRequestBody(method)) {
            if (!TextUtils.isEmpty(name)) {
                if (value instanceof File
                        || value instanceof InputStream
                        || value instanceof byte[]) {
                    this.fileParams.add(new KeyValue(name, value));
                } else {
                    if (value instanceof List) {
                        ...
                    } else if (value instanceof JSONArray) {
                        ...
                    } else if (value.getClass().isArray()) {
                        ...
                        }
                    } else {
                        this.bodyParams.add(new KeyValue(name, value));
                    }
                }
            } else {
                this.bodyContent = value.toString();
            }
        } else {
           ...
        }
    }

这个时候还没有设置请求的方式,例如GET、POST等,所以mothod属性为null。而value为String类型的参数,所以name和value被以KeyValue结构的形式保存在bodyParams中。

网络请求

下文以x.http().post(requestParams, new Callback.CommonCallback<String>() {}过程为例,逐步查看xUtils3调用流程。

x.http()

    public static HttpManager http() {
        if (Ext.httpManager == null) {
            HttpManagerImpl.registerInstance();
        }
        return Ext.httpManager;
    }

    public static void registerInstance() {
        if (instance == null) {
            synchronized (lock) {
                if (instance == null) {
                    instance = new HttpManagerImpl();
                }
            }
        }
        x.Ext.setHttpManager(instance);
    }

    public static void setHttpManager(HttpManager httpManager) {
        Ext.httpManager = httpManager;
    }

第一次调用的时候会初始化Ext#imageManager对象为HttpManagerImpl,以后所有HTTP/HTTPS相关调用都通过HttpManagerImpl管理。

HttpManagerImpl.post()

public final class HttpManagerImpl implements HttpManager {

    @Override
    public <T> Callback.Cancelable post(RequestParams entity, Callback.CommonCallback<T> callback) {
        return request(HttpMethod.POST, entity, callback);
    }

    @Override
    public <T> Callback.Cancelable request(HttpMethod method, RequestParams entity, Callback.CommonCallback<T> callback) {
        entity.setMethod(method);
        Callback.Cancelable cancelable = null;
        if (callback instanceof Callback.Cancelable) {
            cancelable = (Callback.Cancelable) callback;
        }
        HttpTask<T> task = new HttpTask<T>(entity, cancelable, callback);
        return x.task().start(task);
    }
}

这里以HttpMethod == HttpMethod.POST,entity为构造的请求参数,Callback.CommonCallback泛型为String查看流程。
首先设置RequestParams中请求方式为HttpMethod.POST,Callback.CommonCallback没有实现Callback.Cancelable接口,所以这里的if语句不成立,即cancelable为null。接下来构建HttpTask对象。跟进。

public class HttpTask<ResultType> extends AbsTask<ResultType> implements ProgressHandler {

    private static final PriorityExecutor HTTP_EXECUTOR = new PriorityExecutor(5, true);

    public HttpTask(RequestParams params, Callback.Cancelable cancelHandler,
                    Callback.CommonCallback<ResultType> callback) {
        super(cancelHandler);
        this.params = params;
        this.callback = callback;
        if (callback instanceof Callback.CacheCallback) {
            this.cacheCallback = (Callback.CacheCallback<ResultType>) callback;
        }
        ...
        if (params.getExecutor() != null) {
            this.executor = params.getExecutor();
        } else {
            if (cacheCallback != null) {
                this.executor = CACHE_EXECUTOR;
            } else {
                this.executor = HTTP_EXECUTOR;
            }
        }
    }
}

我们没有使用自定义的Executor(可以通过RequestParams.setExecutor()设置),所以params.getExecutor()返回是null,前文也提过CommonCallback没有实现CacheCallback,所以第一个if语句不成立,即cacheCallback为null。即,在HttpTask的构造函数中除了赋值params、callback之外,最主要的是指定了执行请求的线程池为HTTP_EXECUTOR。下面跟进看下这个HTTP_EXECUTOR。

FIFO线程池

public class PriorityExecutor implements Executor {

    private static final int CORE_POOL_SIZE = 5;
    private static final int MAXIMUM_POOL_SIZE = 256;
    private static final int KEEP_ALIVE = 1;
    private static final AtomicLong SEQ_SEED = new AtomicLong(0);

    private static final ThreadFactory sThreadFactory = new ThreadFactory() {
        private final AtomicInteger mCount = new AtomicInteger(1);

        @Override
        public Thread newThread(Runnable runnable) {
            return new Thread(runnable, "xTID#" + mCount.getAndIncrement());
        }
    };

    /**
     * @param poolSize 工作线程数
     * @param fifo     优先级相同时, 等待队列的是否优先执行先加入的任务.
     */
    public PriorityExecutor(int poolSize, boolean fifo) {
        BlockingQueue<Runnable> mPoolWorkQueue =
                new PriorityBlockingQueue<Runnable>(MAXIMUM_POOL_SIZE, fifo ? FIFO_CMP : FILO_CMP);
        mThreadPoolExecutor = new ThreadPoolExecutor(
                poolSize,
                MAXIMUM_POOL_SIZE,
                KEEP_ALIVE,
                TimeUnit.SECONDS,
                mPoolWorkQueue,
                sThreadFactory);
    }

    private static final Comparator<Runnable> FIFO_CMP = new Comparator<Runnable>() {
        @Override
        public int compare(Runnable lhs, Runnable rhs) {
            if (lhs instanceof PriorityRunnable && rhs instanceof PriorityRunnable) {
                PriorityRunnable lpr = ((PriorityRunnable) lhs);
                PriorityRunnable rpr = ((PriorityRunnable) rhs);
                int result = lpr.priority.ordinal() - rpr.priority.ordinal();
                return result == 0 ? (int) (lpr.SEQ - rpr.SEQ) : result;
            } else {
                return 0;
            }
        }
    };

    @Override
    public void execute(Runnable runnable) {
        if (runnable instanceof PriorityRunnable) {
            ((PriorityRunnable) runnable).SEQ = SEQ_SEED.getAndIncrement();
        }
        mThreadPoolExecutor.execute(runnable);
    }
}

自定义了一个线程池,核心线程数是5,最大256,线程存活时间为1s,fifo(first in first out)类型。在执行Runnable之前,给PriorityRunnable的SEQ属性赋值(每次+1),并对比SEQ的值实现优先级。优先级相同时,SEQ值小的先执行。

初始化HttpTask之后,调用了x.task().start(task),x.task()返回Ext.taskController,实际返回是TaskControllerImpl对象,详见x$Ext中static代码块。所以实际上调用的是TaskControllerImpl.start()。

管理任务

public final class TaskControllerImpl implements TaskController {
    @Override
    public <T> AbsTask<T> start(AbsTask<T> task) {
        TaskProxy<T> proxy = null;
        if (task instanceof TaskProxy) {
            proxy = (TaskProxy<T>) task;
        } else {
            proxy = new TaskProxy<T>(task);
        }
        try {
            proxy.doBackground();
        } catch (Throwable ex) {
            LogUtil.e(ex.getMessage(), ex);
        }
        return proxy;
    }

    /*package*/ TaskProxy(AbsTask<ResultType> task) {
        super(task);
        this.task = task;
        this.task.setTaskProxy(this);
        this.setTaskProxy(null);
        Executor taskExecutor = task.getExecutor();
        if (taskExecutor == null) {
            taskExecutor = sDefaultExecutor;
        }
        this.executor = taskExecutor;
    }
}

任务代理

首先,将HttpTask包装成TaskProxy,然后执行TaskProxy.doBackground()。包装成TaskProxy对象的过程无非就是设置代理任务。ps:目前没看出这个TaskProxy存在的意义,只有一个HttpTask,难道是为了可拓展?重点看TaskProxy.doBackground()。

/*package*/ class TaskProxy<ResultType> extends AbsTask<ResultType> {
    @Override
    protected final ResultType doBackground() throws Throwable {
        this.onWaiting();
        PriorityRunnable runnable = new PriorityRunnable(
                task.getPriority(),
                new Runnable() {
                    @Override
                    public void run() {
                        try {
                            // 等待过程中取消
                            if (callOnCanceled || TaskProxy.this.isCancelled()) {
                                throw new Callback.CancelledException("");
                            }

                            // start running
                            TaskProxy.this.onStarted();

                            if (TaskProxy.this.isCancelled()) { // 开始时取消
                                throw new Callback.CancelledException("");
                            }

                            // 执行task, 得到结果.
                            task.setResult(task.doBackground());
                            TaskProxy.this.setResult(task.getResult());

                            // 未在doBackground过程中取消成功
                            if (TaskProxy.this.isCancelled()) {
                                throw new Callback.CancelledException("");
                            }

                            // 执行成功
                            TaskProxy.this.onSuccess(task.getResult());
                        } catch (Callback.CancelledException cex) {
                            TaskProxy.this.onCancelled(cex);
                        } catch (Throwable ex) {
                            TaskProxy.this.onError(ex, false);
                        } finally {
                            TaskProxy.this.onFinished();
                        }
                    }
                });
        this.executor.execute(runnable);
        return null;
    }
}

this.onWaiting()的作用是将任务置为等待状态,对阅读代码无影响,继续。PriorityRunnable实现了Runnable接口,为传递进来的Runnable对象添加了priority属性,priority默认为3(优先级为0、1、2、3、4、5、6,数字越小,优先级越高)。之后会将PriorityRunnable添加进HTTP_EXECUTOR并依据优先级执行。callOnCanceled默认为false,之后设置任务状态为started,回调onStarted()方法。这些都不是重点,重点在下面两行:

// 执行task, 得到结果.
task.setResult(task.doBackground());
TaskProxy.this.setResult(task.getResult());

正室不死,代理终究还是代理。在这里调用了HttpTask.doBackground()。看样子真正的执行请求都在这里,跟进。

    protected ResultType doBackground() throws Throwable {
        ...
        ResultType result = null;
        // 获取LoadType
        resolveLoadType();
        // 创建真正的网络请求
        request = createNewRequest();
        ...
        // 是否重试,默认2次
        boolean retry = true;
        // 已经重试的次数
        int retryCount = 0;
        Throwable exception = null;
        HttpRetryHandler retryHandler = this.params.getHttpRetryHandler();
        if (retryHandler == null) {
            retryHandler = new HttpRetryHandler();
        }
        // 设置最大重试次数
        retryHandler.setMaxRetryCount(this.params.getMaxRetryCount());
        ...
        Object cacheResult = null;
            ...

        if (trustCache == null) {
            trustCache = false;
        }
        ...
        // 发起请求
        retry = true;
        while (retry) {
            retry = false;

            try {
                if (this.isCancelled()) {
                    throw new Callback.CancelledException("cancelled before request");
                }

                // 由loader发起请求, 拿到结果.
                this.request.close(); // retry 前关闭上次请求

                try {
                    clearRawResult();
                    // 开始请求工作
                    LogUtil.d("load: " + this.request.getRequestUri());
                    requestWorker = new RequestWorker();
                    // 真正开始请求
                    requestWorker.request();
                    if (requestWorker.ex != null) {
                        throw requestWorker.ex;
                    }
                    rawResult = requestWorker.result;
                } catch (Throwable ex) {
                    clearRawResult();
                    i...
                }

                if (prepareCallback != null) {
                    ...
                } else {
                    result = (ResultType) rawResult;
                }
                ...
            } catch (HttpRedirectException redirectEx) {
                retry = true;
                LogUtil.w("Http Redirect:" + params.getUri());
            } catch (Throwable ex) {
                switch (this.request.getResponseCode()) {
                    case 204: // empty content
                    case 205: // empty content
                    case 304: // disk cache is valid.
                        return null;
                    default: {
                        exception = ex;
                        if (this.isCancelled() && !(exception instanceof Callback.CancelledException)) {
                            exception = new Callback.CancelledException("canceled by user");
                        }
                        retry = retryHandler.canRetry(this.request, exception, ++retryCount);
                    }
                }
            }

        }

        if (exception != null && result == null && !trustCache) {
            hasException = true;
            throw exception;
        }

        return result;
    }

有些长,我们一点点的看。首先,ResultType肯定是我们传递进来的泛型String。resolveLoadType()为loadType赋值,港真,这里的loadType和ResultType是一样的。没搞明白为什么ResultType能解决的事情,又定义了一个loadType属性。难道是为了好区分ResultType是要返回的类型,loadType是要解析的类型?实际上两者是一样的,在这里都是String。非要说区别的话,ResultType是String,loadType为String.class。

请求参数的处理

    // 初始化请求参数
    private UriRequest createNewRequest() throws Throwable {
        // init request
        params.init();
        UriRequest result = UriRequestFactory.getUriRequest(params, loadType);
        result.setCallingClassLoader(callback.getClass().getClassLoader());
        result.setProgressHandler(this);
        this.loadingUpdateMaxTimeSpan = params.getLoadingUpdateMaxTimeSpan();
        this.update(FLAG_REQUEST_CREATED, result);
        return result;
    }

在params.init()中,主要是设置信任所有证书。主要关注点在下面的创建UriRequest对象。

    public static UriRequest getUriRequest(RequestParams params, Type loadType) throws Throwable {

        // get scheme
        String scheme = null;
        String uri = params.getUri();
        int index = uri.indexOf(":");
        if (index > 0) {
            scheme = uri.substring(0, index);
        } else if (uri.startsWith("/")) {
            scheme = "file";
        }

        // get UriRequest
        if (!TextUtils.isEmpty(scheme)) {
            Class<? extends UriRequest> cls = SCHEME_CLS_MAP.get(scheme);
            if (cls != null) {
                Constructor<? extends UriRequest> constructor
                        = cls.getConstructor(RequestParams.class, Class.class);
                return constructor.newInstance(params, loadType);
            } else {
                if (scheme.startsWith("http")) {
                    return new HttpRequest(params, loadType);
                } else if (scheme.equals("assets")) {
                    return new AssetsRequest(params, loadType);
                } else if (scheme.equals("file")) {
                    return new LocalFileRequest(params, loadType);
                } else {
                    throw new IllegalArgumentException("The url not be support: " + uri);
                }
            }
        } else {
            throw new IllegalArgumentException("The url not be support: " + uri);
        }
    }

获取scheme,这里以https分析。这里好像还整个缓存Map,不管有没有缓存,返回的都是HttpRequest对象,只是来源不一样,这里就不具体分析这个存取的过程。实例化HttpRequest的时候,还有些文章。下面跟进。

public class HttpRequest extends UriRequest {
    /*package*/ HttpRequest(RequestParams params, Type loadType) throws Throwable {
        super(params, loadType);
    }
}

public abstract class UriRequest implements Closeable {
    protected final Loader<?> loader;
    /*package*/ UriRequest(RequestParams params, Type loadType) throws Throwable {
        this.params = params;
        this.queryUrl = buildQueryUrl(params);
        this.loader = LoaderFactory.getLoader(loadType, params);
    }
}

运用工厂模式,通过LoaderFactory获取了一个Loader对象,这个对象在后面有很大的作用。先跟进看下。

public final class LoaderFactory {

    private LoaderFactory() {
    }
    private static final HashMap<Type, Loader> converterHashMap = new HashMap<Type, Loader>();

    static {
        converterHashMap.put(String.class, new StringLoader());
        ...
    }

    @SuppressWarnings("unchecked")
    public static Loader<?> getLoader(Type type, RequestParams params) {
        Loader<?> result = converterHashMap.get(type);
        if (result == null) {
            result = new ObjectLoader(type);
        } else {
            result = result.newInstance();
        }
        result.setParams(params);
        return result;
    }
}

传递进来的type为String.class,所以调用StringLoader.newInstance()。这里并不是反射,newInstance()只是个普通方法,返回StringLoader对象。拓展的有些远了,回到HttpTask.doBackground()。大概屡一下思路:现在已经将解析出loadType为String.class,HttpRequest对象赋值给request,并在在实例化HttpRequest对象的过程中设置Loader

retry机制

在HttpTask.doBackground()中定义了一个局部变量retry,默认为true。并通过retryHandler.setMaxRetryCount(this.params.getMaxRetryCount())设置retry数量为2(默认)。white(retry)中首先把retry设置为false,即“期望”一次请求成功。如果中途出现HttpRedirectException异常或者抛出Throwable并且responseCode不等于204、205、304,那么会再执行一遍while循环。其中HttpRedirectException异常是无限次retry(这点感觉还是计数要好一些),抛出Throwable才会对retry次数进行处理。下面是整个流程的分析。

        // 发起请求
        retry = true;
        while (retry) {
            retry = false;
                ...             
                try {
                    requestWorker = new RequestWorker();
                    requestWorker.request();
                    if (requestWorker.ex != null) {
                        throw requestWorker.ex;
                    }
                } catch (Throwable ex) {
                    ...
                    throw ex;
                }
                ...
            } catch (HttpRedirectException redirectEx) {
                retry = true;
                LogUtil.w("Http Redirect:" + params.getUri());
            } catch (Throwable ex) {
                switch (this.request.getResponseCode()) {
                    case 204: // empty content
                    case 205: // empty content
                    case 304: // disk cache is valid.
                        return null;
                    default: {
                        ...
                        retry = retryHandler.canRetry(this.request, exception, ++retryCount);
                    }
                }
            }

        }


    private final class RequestWorker {
        /*private*/ Object result;
        /*private*/ Throwable ex;

        private RequestWorker() {
        }

        public void request() {
            try {
                ...
                try {
                    this.result = request.loadResult();
                } catch (Throwable ex) {
                    this.ex = ex;
                }

                if (this.ex != null) {
                    throw this.ex;
                }
            } catch (Throwable ex) {
                this.ex = ex;
                ...
                if (errorCode == 301 || errorCode == 302) {//重定向
                    HttpTask.this.params = redirectParams;
                    HttpTask.this.request = createNewRequest();
                    this.ex = new HttpRedirectException(errorCode, httpEx.getMessage(), httpEx.getResult());
                }
            } finally {
               ...
            }
        }
    }

正常的请求失败,会通过retryHandler.canRetry(),将retry置为true,最多执行两次retry。让我疑惑的地方在于重定向的处理。在requestWorker.request()中,如果有重定向,会抛出HttpRedirectException。但是在HttpTask#doBackground()中

                try {
                    if (requestWorker.ex != null) {
                        throw requestWorker.ex;
                    }
                } catch (Throwable ex) {
                    clearRawResult();
                    if (this.isCancelled()) {
                        throw new Callback.CancelledException("cancelled during request");
                    } else {
                        throw ex;
                    }
                }

这里向上转型为Throwable并抛出,从而进入外层的

            } catch (HttpRedirectException redirectEx) {
                retry = true;
                LogUtil.w("Http Redirect:" + params.getUri());
            } catch (Throwable ex) {
                switch (this.request.getResponseCode()) {
                    case 204: // empty content
                    case 205: // empty content
                    case 304: // disk cache is valid.
                        return null;
                    default: {
                        exception = ex;
                        if (this.isCancelled() && !(exception instanceof Callback.CancelledException)) {
                            exception = new Callback.CancelledException("canceled by user");
                        }
                        retry = retryHandler.canRetry(this.request, exception, ++retryCount);
                    }
                }
            }

正常应该进入HttpRedirectException的,但是向上转型成Throwable之后就只能进入下面的catch代码块中。那么HttpRedirectException存在的意义在哪里?希望明白的给指点下。

真正的请求

requestWorker = new RequestWorker();
requestWorker.request();

HttpTask.doBackground()中请求其实只有这两行代码。RequestWorker是HttpTask的一个final内部类,requestWorker.request()方法内部会设置拦截器,处理重定向等,这些暂时不是关注的重点。总之先把流程跑通再说。

    private final class RequestWorker {
        /*private*/ Object result;
        public void request() {
            ...
            this.result = request.loadResult();
            ...
        }
    }

request实际上是HttpRequest对象。

public class HttpRequest extends UriRequest {
    @Override
    public Object loadResult() throws Throwable {
        isLoading = true;
        return super.loadResult();
    }
}

public abstract class UriRequest implements Closeable {
    public Object loadResult() throws Throwable {
        return this.loader.load(this);
    }
}

/*package*/ class StringLoader extends Loader<String> {

   @Override
    public String load(final UriRequest request) throws Throwable {
        request.sendRequest();
        return this.load(request.getInputStream());
    }

    @Override
    public String load(final InputStream in) throws Throwable {
        resultStr = IOUtil.readStr(in, charset);
        return resultStr;
    }
}

经过层层调用最终调用request.sendRequest(),即HttpRequest.sendRequest()。看方法名字也知道干撒的了,代码太长这里就不贴了,概述下主要作用:依据之前的各种参数设置请求,发起请求,获取返回状态码,如果有自定义拦截器的话,还会调用beforeRequest()、afterRequest()。接下来调用request.getInputStream()获取输入流,并使用IOUtil.readStr()转换之后返回String,最后在RequestWorker.request()中将返回的String赋值给result。一切顺利的话,接着回到Task.doBackground()。执行task.setResult(task.doBackground())。之后翻来覆去的调用get/setResult好像暂时没有用,可能是其他情况下的处理吧。不过也没有什么影响,接着会调用TaskProxy.this.onSuccess(task.getResult())。在这个方法中通过Handler(获取了MainLooper)在主线程中调用callback.onSuccess(result)。如果出现异常会则调用TaskProxy.this.onError(ex, false),不管成功还是失败都会调用finally中的TaskProxy.this.onFinish(ex, false)过程都是类似的,这里就不再赘述。至此,整个网络请求包括回调结束。

取消网络请求

取消网络请求会调用cancelable.cancel(),这里的cancelable是HttpManagerImpl.request()返回的TaskProxy对象。即等价于执行TaskProxy.cancle()。这个方法的具体实现在父类AbsTask中。

    @Override
    public final synchronized void cancel() {
        if (!this.isCancelled) {
            this.isCancelled = true;
            cancelWorks();
            if (cancelHandler != null && !cancelHandler.isCancelled()) {
                cancelHandler.cancel();
            }
            if (this.state == State.WAITING || (this.state == State.STARTED && isCancelFast())) {
                if (taskProxy != null) {
                    taskProxy.onCancelled(new Callback.CancelledException("cancelled by user"));
                    taskProxy.onFinished();
                } else if (this instanceof TaskProxy) {
                    this.onCancelled(new Callback.CancelledException("cancelled by user"));
                    this.onFinished();
                }
            }
        }
    }

AbsTask实现了Cancelable接口,所以这里的cancelHandler不为null,但是cancelHandler.isCancelled()返回true,所以不会循环调用cancelHandler.cancel()。任务被创建后就进入了WAITING状态,所以会调用TaskProxy.onCancelled()和TaskProxy.onFinished()。在这两个回调方法中分别通过Hanlder在主线程中调用HttpTask的onCanclled()和onFinished()方法,之后再调用接口回调中的onCanclled()和onFinished()方法。需要注意的是HttpTask.onFinished()方法。

    protected void onFinished() {
        if (tracker != null) {
            tracker.onFinished(request);
        }
        x.task().run(new Runnable() {
            @Override
            public void run() {
                closeRequestSync();
            }
        });
        callback.onFinished();
    }

    private void closeRequestSync() {
        clearRawResult();
        IOUtil.closeQuietly(request);
    }
    IoUtil#
    public static void closeQuietly(Closeable closeable) {
        if (closeable != null) {
            try {
                closeable.close();
            } catch (Throwable ignored) {
                LogUtil.d(ignored.getMessage(), ignored);
            }
        }
    }
    HttpRequest#
    public void close() throws IOException {
        if (inputStream != null) {
            IOUtil.closeQuietly(inputStream);
            inputStream = null;
        }
        if (connection != null) {
            connection.disconnect();
            //connection = null;
        }
    }

在调用callback.onFinished()的同时异步执行线程,清除请求结果和关闭链接。这个过程对调用者来说是异步的无感知的。

总结

  1. xUtils3使用PriorityExecutor(FIFO线程池)+PriorityRunnable(带优先级的Runnable)实现网络请求。
  2. 通过传入MainLooper的Handler实现由子线程到主线程的切换,并调用相应的回调方法。
  3. 支持retry,默认2次。
  4. 通过给Task设置不同状态,实现不同状态下的处理,主要是为了实现cancle()。
  5. 自带拓展了不同类型的Callback和Loader,满足日常开发(特殊需求可仿照实现)。

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