关于PubNub History API的页面指出
history() 函数返回一个最多包含 100 条消息的列表、开始时间标记和结束时间标记。
有没有办法检索超过 100 条消息？
我目前不是 PubNub 的付费客户。
问问题
3561 次
3 回答
5
PubNub 加载历史超过 100 条消息
有时，您希望在线性数据流上及时回切。通常您会希望在不同的粒度级别上执行此操作。这就是 PubNub 存储和播放 API 提供最大灵活性的原因。然而，有时使用首选结果集加载数据最终会有点棘手。
在时间轴上加载交易历史记录时，您可能需要考虑几个考虑因素，这些时间轴可能跨越交易集中的数百万条消息。有一些不错的选择可供您使用，我们现在将介绍其中的两个。这些示例将使用 JavaScript 编码。第一个示例通过抓取过去 24 小时内每个小时开始的快照来加载数据摘要。第二个示例向您展示了如何加载所有事务的完整细节和最大粒度。
所有参考文件都可以在这个GIST 上找到：Loading History from PubNub Mt.Gox Trades
示例 PubNub Mt.Gox 历史 JavaScript 用法
<script src="https://cdn.pubnub.com/pubnub.min.js"></script>
<script src="mtgox-history.js"></script>
<script>(function(){
// LOAD HOURLY SUMMARY
MTGOX.history.hourly({
channel : 'd5f06780-30a8-4a48-a2f8-7ed181b4a13f',
data : function(response) { console.log(JSON.stringify(response)) },
error : function() { console.log("NETWORK ERROR") }
});
// LOAD ALL WITH LIMITER OPTION
MTGOX.history.full({
limit : 500, // SET LIMIT AS HIGH AS NEEDED TO LOAD MORE!
channel : 'd5f06780-30a8-4a48-a2f8-7ed181b4a13f',
data : function(messages) { console.log(messages) },
error : function(e) { console.log("NETWORK ERROR") }
});
})();</script>
注意：运行
MTGOX.history.hourly()方法将生成过去 24 小时内每小时的快照列表。注意：运行
MTGOX.history.full()方法将生成包含大量数据的最高分辨率细节。您可以根据需要获取完整转储或部分转储；并且您应该增加limit参数以获取更多数据点。
以下 JavaScript 文件将为您提供MTGOX界面。
PubNub Mt.Gox 历史 JavaScript 加载器
//
// mtgox-history.js
//
(function(){
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// INITIALIZE PUBNUB
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
var pubnub = PUBNUB.init({
subscribe_key : 'sub-c-50d56e1e-2fd9-11e3-a041-02ee2ddab7fe'
});
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// MTGOX HISTORY INTERFACE
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
window.MTGOX = {
history : {
hourly : hourly,
full : full
}
};
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// GET ALL DATA FOREVER (WITH LIMIT OF COURSE)
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
/*
MTGOX.history.full({
limit : 1000,
channel : 'd5f06780-30a8-4a48-a2f8-7ed181b4a13f',
data : function(messages) { console.log(messages) },
error : function(e) { console.log("NETWORK ERROR") }
});
*/
function full(args) {
var chan = args['channel'] ||'d5f06780-30a8-4a48-a2f8-7ed181b4a13f'
, callback = args['data'] || function(){}
, error = args['error'] || function(){}
, limit = +args['limit'] || 5000
, start = 0
, count = 100
, history = []
, params = {
channel : chan,
count : count,
callback : function(messages) {
var msgs = messages[0];
start = messages[1];
params.start = start;
PUBNUB.each( msgs.reverse(), function(m) {history.push(m)} );
if (history.length >= limit) return callback(history);
if (msgs.length < count) return callback(history);
count = 100;
add_messages();
},
error : function(e) {
callback(history);
error(history);
}
};
add_messages();
function add_messages() { pubnub.history(params) }
}
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// GET 24 HOURS IN HOURLY INCREMENTS
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
/*
MTGOX.history.hourly({
channel : 'd5f06780-30a8-4a48-a2f8-7ed181b4a13f',
data : function(response) { console.log(response) },
error : function() { console.log('ERROR') }
});
*/
function hourly(setup) {
var limit = 24;
var count = 0;
var chan = setup['channel'] ||'d5f06780-30a8-4a48-a2f8-7ed181b4a13f';
var cb = setup['data'] || function(){};
var eb = setup['error'] || function(){};
var now = new Date();
now.setUTCHours(0);
now.setUTCMinutes(0);
now.setUTCSeconds(0);
now.setUTCMilliseconds(0);
var utc_now = now.getTime();
var vectors = [];
PUBNUB.each( (new Array(limit)).join(',').split(','), function( _, d ) {
var day = utc_now - 3600000 * d;
pubnub.history({
limit : 1,
channel : chan,
start : day * 10000,
error : function() { count++; eb(); },
callback : function(messages) {
// DONE?
if (++count == limit) return cb(vectors);
// ADD TIME SLICES
var res = +(((messages[0][0]||{}).ticker||{}).avg||{}).value;
res && vectors.push([ new Date(day).getUTCHours(), res ]);
// KEEP IT SORTED
vectors.sort(function(a,b){ return a[0] > b[0] && -1 || 1 });
}
})
} );
}
})();
用于代码、深度和交易的 Mt.Gox PubNub 频道列表
以下是 Mt.Gox 数据馈送选项提供的频道列表，您可以在历史channel参数字段中使用。
{
"TICKER.ltcgbp": "0102A446-E4D4-4082-8E83-CC02822F9172",
"TICKER.ltccny": "0290378C-E3D7-4836-8CB1-2BFAE20CC492",
"DEPTH.btchkd": "049F65DC-3AF3-4FFD-85A5-AAC102B2A579",
"DEPTH.btceur": "057BDC6B-9F9C-44E4-BC1A-363E4443CE87",
"TICKER.nmcaud": "08C65460-CBD9-492E-8473-8507DFA66AE6",
"TICKER.btceur": "0BB6DA8B-F6C6-4ECF-8F0D-A544AD948C15",
"DEPTH.btckrw": "0C84BDA7-E613-4B19-AE2A-6D26412C9F70",
"DEPTH.btccny": "0D1ECAD8-E20F-459E-8BED-0BDCF927820F",
"TICKER.btccad": "10720792-084D-45BA-92E3-CF44D9477775",
"DEPTH.btcchf": "113FEC5F-294D-4929-86EB-8CA4C3FD1BED",
"TICKER.ltcnok": "13616AE8-9268-4A43-BDF7-6B8D1AC814A2",
"TICKER.ltcusd": "1366A9F3-92EB-4C6C-9CCC-492A959ECA94",
"TICKER.btcbtc": "13EDFF67-CFA0-4D99-AA76-52BD15D6A058",
"TICKER.ltccad": "18B55737-3F5C-4583-AF63-6EB3951EAD72",
"TICKER.nmccny": "249FDEFD-C6EB-4802-9F54-064BC83908AA",
"DEPTH.btcusd": "24E67E0D-1CAD-4CC0-9E7A-F8523EF460FE",
"TICKER.btcchf": "2644C164-3DB7-4475-8B45-C7042EFE3413",
"DEPTH.btcaud": "296EE352-DD5D-46F3-9BEA-5E39DEDE2005",
"TICKER.btcczk": "2A968B7F-6638-40BA-95E7-7284B3196D52",
"TICKER.btcsgd": "2CB73ED1-07F4-45E0-8918-BCBFDA658912",
"TICKER.nmcjpy": "314E2B7A-A9FA-4249-BC46-B7F662ECBC3A",
"TICKER.btcnmc": "36189B8C-CFFA-40D2-B205-FB71420387AE",
"DEPTH.btcinr": "414FDB18-8F70-471C-A9DF-B3C2740727EA",
"DEPTH.btcsgd": "41E5C243-3D44-4FAD-B690-F39E1DBB86A8",
"TICKER.btcltc": "48B6886F-49C0-4614-B647-BA5369B449A9",
"TICKER.ltceur": "491BC9BB-7CD8-4719-A9E8-16DAD802FFAC",
"TICKER.btcinr": "55E5FEB8-FEA5-416B-88FA-40211541DECA",
"TICKER.ltcjpy": "5AD8E40F-6DF3-489F-9CF1-AF28426A50CF",
"DEPTH.btccad": "5B234CC3-A7C1-47CE-854F-27AEE4CDBDA5",
"TICKER.btcnzd": "5DDD27CA-2466-4D1A-8961-615DEDB68BF1",
"DEPTH.btcgbp": "60C3AF1B-5D40-4D0E-B9FC-CCAB433D2E9C",
"DEPTH.btcnok": "66DA7FB4-6B0C-4A10-9CB7-E2944E046EB5",
"DEPTH.btcthb": "67879668-532F-41F9-8EB0-55E7593A5AB8",
"TICKER.btcsek": "6CAF1244-655B-460F-BEAF-5C56D1F4BEA7",
"TICKER.btcnok": "7532E866-3A03-4514-A4B1-6F86E3A8DC11",
"TICKER.btcgbp": "7B842B7D-D1F9-46FA-A49C-C12F1AD5A533",
"TRADE.LAG": "85174711-BE64-4DE1-B783-0628995D7914",
"DEPTH.btcsek": "8F1FEFAA-7C55-4420-ADA0-4DE15C1C38F3",
"DEPTH.btcdkk": "9219ABB0-B50C-4007-B4D2-51D1711AB19C",
"DEPTH.btcjpy": "94483E07-D797-4DD4-BC72-DC98F1FD39E3",
"TICKER.nmcusd": "9AAEFD15-D101-49F3-A2FD-6B63B85B6BED",
"TICKER.ltcaud": "A046600A-A06C-4EBF-9FFB-BDC8157227E8",
"TICKER.btcjpy": "A39AE532-6A3C-4835-AF8C-DDA54CB4874E",
"DEPTH.btcczk": "A7A970CF-4F6C-4D85-A74E-AC0979049B87",
"TICKER.ltcdkk": "B10A706E-E8C7-4EA8-9148-669F86930B36",
"TICKER.btcpln": "B4A02CB3-2E2D-4A88-AEEA-3C66CB604D01",
"TEST": "BAD99F24-FA8B-4938-BFDF-0C1831FC6665",
"TICKER.btcrub": "BD04F720-3C70-4DCE-AE71-2422AB862C65",
"TICKER.nmcgbp": "BF5126BA-5187-456F-8AE6-963678D0607F",
"TICKER.btckrw": "BF85048D-4DB9-4DBE-9CA3-5B83A1A4186E",
"TICKER.btccny": "C251EC35-56F9-40AB-A4F6-13325C349DE4",
"DEPTH.btcnzd": "CEDF8730-BCE6-4278-B6FE-9BEE42930E95",
"TICKER.btchkd": "D3AE78DD-01DD-4074-88A7-B8AA03CD28DD",
"TICKER.btcthb": "D58E3B69-9560-4B9E-8C58-B5C0F3FDA5E1",
"TICKER.btcusd": "D5F06780-30A8-4A48-A2F8-7ED181B4A13F",
"DEPTH.btcrub": "D6412CA0-B686-464C-891A-D1BA3943F3C6",
"TICKER.nmceur": "D8512D04-F262-4A14-82F2-8E5C96C15E68",
"TRADE.btc": "DBF1DEE9-4F2E-4A08-8CB7-748919A71B21",
"TICKER.nmccad": "DC28033E-7506-484C-905D-1C811A613323",
"DEPTH.btcpln": "E4FF055A-F8BF-407E-AF76-676CAD319A21",
"TICKER.btcdkk": "E5CE0604-574A-4059-9493-80AF46C776B3",
"TICKER.btcaud": "EB6AAA11-99D0-4F64-9E8C-1140872A423D"
}
于 2014-01-08T06:12:38.167 回答
1
如需进一步帮助，请参阅https://help.pubnub.com/entries/24113341-How-do-I-Page-Through-Stored-Messages- 联系 PubNub 支持 (help@...)
于 2014-01-07T22:00:16.133 回答
0
下面的 Java 类可用于在这种形式的高级 for 循环中轻松检索和处理长时间范围的历史消息：
PubnubHistoryExcerpt history = new PubnubHistoryExcerpt(pubnub, channel, start, end);
for (Object message : history) {
// do something with the message object
}
消息是即时检索的，因此不会出现内存问题。
下面是完整的代码。main()您可以在类内部的方法中找到完全可运行的使用示例。
我还没有广泛地测试过这个类。欢迎改进。
/*
* PubnubHistoryExcerpt.java
*
* This file is distributed under the FreeBSD License:
*
* Copyright (c) 2014, Daniel S. (http://stackoverflow.com/users/1838726/daniel-s)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation are those
* of the authors and should not be interpreted as representing official policies,
* either expressed or implied, of the FreeBSD Project.
*/
import java.math.BigDecimal;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.pubnub.api.Callback;
import com.pubnub.api.Pubnub;
import com.pubnub.api.PubnubError;
/**
* You can use this class to iterate over historical PubNub messages. The messages are retrieved transparently while you
* iterate over the history excerpt. This class and the returned iterators are thread-safe.
*
* See {@link #main(String[])} for a usage example.
*/
public class PubnubHistoryExcerpt implements Iterable<Object> {
/**
* This main method contains a usage example for this class. It downloads last 3 hour's messages of the MtGox BTC/USD ticker
* channel from PubNub and outputs the timestamp and USD value which are found in the messages.
*/
public static void main(String[] args) throws JSONException {
String PUBNUB_SUBSCRIBE_KEY_MTGOX = "sub-c-50d56e1e-2fd9-11e3-a041-02ee2ddab7fe";
String PUBNUB_CHANNEL_MTGOX_TICKER_BTCUSD = "d5f06780-30a8-4a48-a2f8-7ed181b4a13f";
Pubnub pubnub = new Pubnub(null, PUBNUB_SUBSCRIBE_KEY_MTGOX);
long ONE_HOUR_IN_MILLIS = 60 * 60 * 1000;
long end = System.currentTimeMillis();
long start = end - 3 * ONE_HOUR_IN_MILLIS;
// convert from milliseconds as time unit (10^-3 seconds) to
// pubnub's better-than-microsecond precision time units (10^-7 seconds)
start *= 10000;
end *= 10000;
PubnubHistoryExcerpt history = new PubnubHistoryExcerpt(pubnub, PUBNUB_CHANNEL_MTGOX_TICKER_BTCUSD, start, end);
DefaultDateFormat dateFormat = DefaultDateFormat.create();
for (Object message : history) {
JSONObject messageJson = (JSONObject) message;
JSONObject ticker = messageJson.getJSONObject("ticker");
long instant = ticker.getLong("now");
BigDecimal value = new BigDecimal(ticker.getJSONObject("last_local").getString("value"));
instant /= 1000; // convert from microseconds to milliseconds
System.out.println(dateFormat.format(instant) + ": " + value);
}
System.exit(0);
}
/**
* This is the maximum number of messages to fetch in one batch. If you fetch many messages, higher numbers improve
* performance. Setting this to a value higher than 100 doesn't have an effect, because Pubnub currently doesn't
* support fetching more than this many messages at once.
*/
private static final int BATCH_SIZE = 100;
private final Pubnub pubnub;
private final String channel;
private final long start;
private final long end;
/**
* Constructs a new excerpt over which you can iterate. Insances represent an excerpt. No retrieval operations are
* started unless you call iterator().next() for the first time.
*
* @param pubnub
* The Pubnub connection to use for retrieving messages.
* @param channel
* The channel for which to retrieve historical messages.
* @param start
* The beginning of the time interval for which to retrieve messages, in pubnub's time units (10^-7
* seconds, so milliseconds * 10000) since 1970-01-01 00:00:00).
* @param end
* The end of the time interval for which to retrieve messages, in pubnub's time units (10^-7 seconds, so
* milliseconds * 10000) since 1970-01-01 00:00:00).
*/
private PubnubHistoryExcerpt(Pubnub pubnub, String channel, long start, long end) {
this.pubnub = pubnub;
this.channel = channel;
this.start = start;
this.end = end;
}
public Iterator<Object> iterator() {
return new Iter();
}
private class Iter implements Iterator<Object> {
/**
* This list is used as a fifo buffer for messages retrieves through this iterator. It also acts as the main
* synchronization lock for synchronizing access between threads accessing this class as an iterator and threads
* calling back from the Pubnub API.
*/
private LinkedList<Object> buffer = new LinkedList<Object>();
/**
* This field stores the end of the time range of the previous batch retrieval, in Pubnub time units (10th of a
* microsecond, so milliseconds*10000). For the following batch retrieval, this is used as the start time for
* retrieving the following messages.
*/
private long prevBatchTimeRangeEnd = PubnubHistoryExcerpt.this.start;
/**
* Retrieval of messages is handled asynchronously. That means that exceptions which are thrown during retrieval
* can't automatically be propagated through to the code which invokes <code>next()</code> or
* <code>hasNext()</code> . Therefor, such an exception is stored temporarily in this field and then re-thrown
* from within <code>next()</code> or <code>hasNext()</code>.
*/
private Exception caughtDuringRetrieval = null;
/**
* This object is used to wait on and to notify about updates of the buffer.
*/
private Object notifier = new Object();
/**
* Because of spurious wakeups that can happen during wait(), this field is necessary to tell the waiting thread
* if retrieval is still running.
*/
private boolean retrieving = false;
/**
* The callback object to use for retrieving messages. This is stored in a field here for re-use. This is a
* compromise between performance and low memory footprint, slightly in favor of performance.
*/
private InternalCallback internalCallback = new InternalCallback();
private void retrieveNextBatch() {
synchronized (notifier) {
this.retrieving = true;
// String startStr = DefaultDateFormat.create().format(prevBatchTimeRangeEnd / 10000);
// String endStr = DefaultDateFormat.create().format(end / 10000);
// System.out.println("fetching from " + startStr + " till " + endStr);
if (Iter.this.prevBatchTimeRangeEnd < PubnubHistoryExcerpt.this.end) {
PubnubHistoryExcerpt.this.pubnub.history( //
PubnubHistoryExcerpt.this.channel, //
Iter.this.prevBatchTimeRangeEnd, //
PubnubHistoryExcerpt.this.end, //
BATCH_SIZE, //
false, //
Iter.this.internalCallback //
);
waitUntilNextBatchRetrievalFinished();
}
}
}
private void waitUntilNextBatchRetrievalFinished() {
while (this.retrieving) {
try {
this.notifier.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private class InternalCallback extends Callback {
@Override
public void successCallback(String channel, Object message) {
synchronized (Iter.this.notifier) {
try {
processSuccessCallback(channel, message);
} catch (Exception e) {
Iter.this.caughtDuringRetrieval = e;
} finally {
Iter.this.retrieving = false;
Iter.this.notifier.notifyAll();
}
}
}
@Override
public void errorCallback(String channel, PubnubError error) {
Iter.this.caughtDuringRetrieval = new Exception("" + //
error.getClass().getName() + ": " + //
error.getErrorString() + //
" (code=" + error.errorCode + "; extendedCode=" + error.errorCodeExtended + ")");
Iter.this.caughtDuringRetrieval.fillInStackTrace();
}
}
private void processSuccessCallback(String channel, Object message) throws JSONException {
if (message == null)
throw new NullPointerException("retrieved message is null");
if (!(message instanceof JSONArray))
throw new RuntimeException("retrieved message is not a " + JSONArray.class.getName());
JSONArray historyMessage = (JSONArray) message;
// System.out.println(historyMessage.toString(2));
JSONArray messageList = extractMessageList(historyMessage);
long batchTimeRangeEnd = extractBatchTimeRangeEnd(historyMessage);
if (batchTimeRangeEnd > 0)
Iter.this.prevBatchTimeRangeEnd = batchTimeRangeEnd;
else
Iter.this.prevBatchTimeRangeEnd = end;
processMessageList(messageList);
}
private void processMessageList(JSONArray messageList) {
int i = 0;
for (; i < messageList.length(); i++) {
JSONObject message;
try {
message = messageList.getJSONObject(i);
} catch (JSONException e) {
String str;
try {
str = messageList.toString(2);
} catch (JSONException secondaryE) {
str = "(couldn't convert messageList to String because of " + secondaryE.toString() + ")";
}
throw new RuntimeException("couldn't extract message at index " + i + " from messageList (messageList:\n" + str
+ "\n(end of messageList)\n)", e);
}
Iter.this.buffer.add(message);
}
}
private long extractBatchTimeRangeEnd(JSONArray historyMessage) {
long batchTimeRangeEnd;
try {
batchTimeRangeEnd = historyMessage.getLong(2);
} catch (JSONException e) {
String str = safeConvertHistoryMessageToString(historyMessage);
throw new RuntimeException("could not extract element 2 (batchTimeRangeEnd) of retrieved historyMessage (historyMessage:\n" + str
+ "\n(end of historyMessage)\n)", e);
}
return batchTimeRangeEnd;
}
private String safeConvertHistoryMessageToString(JSONArray historyMessage) {
String str;
try {
str = historyMessage.toString(2);
} catch (JSONException secondaryE) {
str = "(couldn't convert historyMessage to String because of " + secondaryE.toString() + ")";
}
return str;
}
private JSONArray extractMessageList(JSONArray historyMessage) {
JSONArray messageArJson;
try {
messageArJson = historyMessage.getJSONArray(0);
} catch (JSONException e) {
String str = safeConvertHistoryMessageToString(historyMessage);
throw new RuntimeException("could not extract element 0 (messageList) of retrieved historyMessage (historyMessage:\n" + str
+ "\n(end of historyMessage)\n)", e);
}
return messageArJson;
}
public boolean hasNext() {
synchronized (Iter.this.buffer) {
ensureNotInExceptionState();
if (Iter.this.buffer.isEmpty())
retrieveNextBatch();
return !Iter.this.buffer.isEmpty();
}
}
public Object next() {
synchronized (Iter.this.buffer) {
if (!hasNext()) {
throw new NoSuchElementException("there are no more elements in this iterator");
}
Object result = Iter.this.buffer.removeFirst();
return result;
}
}
private void ensureNotInExceptionState() {
if (caughtDuringRetrieval != null) {
throw new RuntimeException("an exception was caught already by a previous attempt to access this iterator", caughtDuringRetrieval);
}
}
public void remove() {
throw new UnsupportedOperationException(getClass().getName() + " doesn't support remove()");
}
}
}
于 2014-01-12T16:04:49.383 回答