Java tutorial
/******************************************************************************* * Copyright (c) 2011 The Board of Trustees of the Leland Stanford Junior University * as Operator of the SLAC National Accelerator Laboratory. * Copyright (c) 2011 Brookhaven National Laboratory. * EPICS archiver appliance is distributed subject to a Software License Agreement found * in file LICENSE that is included with this distribution. *******************************************************************************/ package edu.stanford.slac.archiverappliance.PBOverHTTP; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.net.URI; import java.net.URISyntaxException; import java.net.URL; import java.sql.Timestamp; import java.util.HashMap; import java.util.List; import java.util.concurrent.Callable; import org.apache.http.HttpEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.log4j.Logger; import org.epics.archiverappliance.Event; import org.epics.archiverappliance.EventStream; import org.epics.archiverappliance.StoragePlugin; import org.epics.archiverappliance.common.BasicContext; import org.epics.archiverappliance.common.TimeUtils; import org.epics.archiverappliance.config.ConfigService; import org.epics.archiverappliance.etl.ConversionFunction; import org.epics.archiverappliance.retrieval.CallableEventStream; import org.epics.archiverappliance.retrieval.postprocessors.PostProcessor; import org.epics.archiverappliance.utils.ui.URIUtils; import edu.stanford.slac.archiverappliance.PB.EPICSEvent; /** * A read-only storage plugin that gets data using the PB/http protocol from a server. * @author mshankar * */ public class PBOverHTTPStoragePlugin implements StoragePlugin { private static Logger logger = Logger.getLogger(PBOverHTTPStoragePlugin.class.getName()); private String accessURL = null; private String desc = "A event stream backed by a .raw response from a remote server."; private String name; private boolean skipExternalServers = false; @Override public List<Callable<EventStream>> getDataForPV(BasicContext context, String pvName, Timestamp startTime, Timestamp endTime, PostProcessor postProcessor) throws IOException { String getURL = accessURL + "?pv=" + pvName + "&from=" + TimeUtils.convertToISO8601String(startTime) + "&to=" + TimeUtils.convertToISO8601String(endTime) + (postProcessor != null ? "&pp=" + postProcessor.getExtension() : "") + (skipExternalServers ? "skipExternalServers=true" : ""); logger.info("URL to fetch data is " + getURL); return getDataBehindURL(getURL, startTime, postProcessor); } public List<Callable<EventStream>> getDataForMultiPVs(BasicContext context, List<String> pvNames, Timestamp startTime, Timestamp endTime, PostProcessor postProcessor) throws IOException { String getURL = accessURL; for (int i = 0; i < pvNames.size(); i++) if (i == 0) getURL += "?pv=" + pvNames.get(i); else getURL += "&pv=" + pvNames.get(i); getURL += "&from=" + TimeUtils.convertToISO8601String(startTime) + "&to=" + TimeUtils.convertToISO8601String(endTime) + (postProcessor != null ? "&pp=" + postProcessor.getExtension() : "") + (skipExternalServers ? "skipExternalServers=true" : ""); logger.info("URL to fetch data is " + getURL); return getDataBehindURL(getURL, startTime, postProcessor); } private List<Callable<EventStream>> getDataBehindURL(String getURL, Timestamp startTime, PostProcessor postProcessor) { try { CloseableHttpClient httpclient = HttpClients.createDefault(); HttpGet getMethod = new HttpGet(getURL); getMethod.addHeader("Connection", "close"); // https://www.nuxeo.com/blog/using-httpclient-properly-avoid-closewait-tcp-connections/ try (CloseableHttpResponse response = httpclient.execute(getMethod)) { if (response.getStatusLine().getStatusCode() == 200) { HttpEntity entity = response.getEntity(); if (entity != null) { logger.debug("Obtained a HTTP entity of length " + entity.getContentLength()); ByteArrayOutputStream bos = new ByteArrayOutputStream(); entity.writeTo(bos); bos.close(); ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray()); InputStreamBackedEventStream isStream = new InputStreamBackedEventStream(bis, startTime); if (isStream.getDescription() != null) { isStream.getDescription().setSource(this.getName()); } else { logger.warn("No desc attached to input stream for url " + getURL); } return CallableEventStream.makeOneStreamCallableList(isStream, postProcessor, true); } else { logger.debug("Obtained empty HTTP entity from " + getURL); } } else { logger.warn("Invalid status code " + response.getStatusLine().getStatusCode() + " when connecting to URL " + getURL); HttpEntity entity = response.getEntity(); if (entity != null) { ByteArrayOutputStream sbuf = new ByteArrayOutputStream(); entity.writeTo(sbuf); logger.warn(sbuf.toString("UTF-8")); } } } } catch (FileNotFoundException fex) { logger.debug("No data from remote site " + getURL); return null; } catch (Throwable t) { logger.warn("Exception fetching data from URL " + getURL, t); } return null; } @Override public boolean appendData(BasicContext context, String pvName, EventStream stream) { throw new RuntimeException("Append Data is not available for HTTP streams"); } @Override public String getDescription() { return desc; } @Override public void initialize(String configURL, ConfigService configService) throws IOException { try { URI srcURI = new URI(configURL); HashMap<String, String> queryNVPairs = URIUtils.parseQueryString(srcURI); if (queryNVPairs.containsKey("rawURL")) { this.setAccessURL(queryNVPairs.get("rawURL")); } else { throw new IOException( "Cannot initialize the pbraw plugin; this needs the URL to the engine/Raw over HTTP to be specified " + configURL); } if (queryNVPairs.containsKey("name")) { name = queryNVPairs.get("name"); } else { name = new URL(this.getAccessURL()).getHost(); logger.debug("Using the default name of " + name + " for this plain pb engine"); } if (queryNVPairs.containsKey("skipExternalServers")) { logger.debug( "Telling the remote server to skip all data from external (potentially ChannelArchiver) servers"); this.skipExternalServers = Boolean.parseBoolean(queryNVPairs.get("skipExternalServers")); } } catch (URISyntaxException ex) { throw new IOException(ex); } } public String getAccessURL() { return accessURL; } public void setAccessURL(String aURL) { this.accessURL = aURL; this.setDesc("PB over HTTP from URL " + aURL); loadPBclasses(); } private static void loadPBclasses() { try { EPICSEvent.ScalarDouble.newBuilder().setSecondsintoyear(0).setNano(0).setVal(0).setSeverity(0) .setStatus(0).build().toByteArray(); } catch (Exception ex) { logger.error(ex.getMessage(), ex); } } public void setDesc(String newDesc) { this.desc = newDesc; } @Override public Event getLastKnownEvent(BasicContext context, String pvName) throws IOException { throw new UnsupportedOperationException(); } @Override public Event getFirstKnownEvent(BasicContext context, String pvName) throws IOException { throw new UnsupportedOperationException(); } @Override public String getName() { return name; } @Override public void renamePV(BasicContext context, String oldName, String newName) throws IOException { // Nothing to do here. } @Override public void convert(BasicContext context, String pvName, ConversionFunction conversionFuntion) throws IOException { // Nothing to do here. } }