2021SC@SDUSC

** 提示

源码展示中笔者会将重载的方法省略，只展示关键方法

探索SolrClient

sdudoc的检索功能主要是通过solr实现的，本人确实很好奇solr框架的源码是如何实现的。

首先我们需要在 application.properties 中配置solr的服务器主机地址。

我们使用 solr 主要是通过SolrClient 类进行操作的，solr 的源码大致如下：

public abstract class SolrClient implements Serializable, Closeable {// 可以用来将Object转为Document对象private DocumentObjectBinder binder;public UpdataResponse add(...) {UpdateRequest req = new UpdateRequest();...req.setCommitWithin(...);return req.process(this, ...);}public UpdateResponse addBeans(String collection, Collection<?> beans, int commitWithinMs) throws SolrServerException, IOException {DocumentObjectBinder binder = this.getBinder();ArrayList<SolrInputDocument> docs =  new ArrayList<>(beans.size());for (Object bean : beans) {docs.add(binder.toSolrInputDocument(bean));}return add(collection, docs, commitWithinMs);}public UpdateResponse commit(String collection, boolean waitFlush, boolean waitSearcher, boolean softCommit)throws SolrServerException, IOException {return new UpdateRequest().setAction(UpdateRequest.ACTION.COMMIT, waitFlush, waitSearcher, softCommit).process(this, collection);}// 其他的都是通过 UpdateRequest 操作的，这里不多赘述...
}

可见，SolrClient 是一个用来包装更新请求 UpdateRequest 的类，便于使用者进行相关的操作。

下面我们来看一下 UpdateRequest 类

可以发现，UpdateRequest有很多成员：

private Map<SolrInputDocument,Map<String,Object>> documents = null;
private Iterator<SolrInputDocument> docIterator = null;
private Map<String,Map<String,Object>> deleteById = null;
private List<String> deleteQuery = null;private boolean isLastDocInBatch = false;

并且构造器内容为：

public UpdateRequest() {super(METHOD.POST, "/update");
}public UpdateRequest(String url) {super(METHOD.POST, url);
}

UpdateRequest 的基本操作如下：

// 无参数add
public UpdateRequest add(final SolrInputDocument doc) {Objects.requireNonNull(doc, "Cannot add a null SolrInputDocument");if (documents == null) {documents = new LinkedHashMap<>();}documents.put(doc, null);return this;
}// 有参数add
public UpdateRequest add(final SolrInputDocument doc, Integer commitWithin, Boolean overwrite) {Objects.requireNonNull(doc, "Cannot add a null SolrInputDocument");if (documents == null) {documents = new LinkedHashMap<>();}Map<String,Object> params = new HashMap<>(2);if (commitWithin != null) params.put(COMMIT_WITHIN, commitWithin);if (overwrite != null) params.put(OVERWRITE, overwrite);documents.put(doc, params);return this;
}// 多个对象add
public UpdateRequest add(final Collection<SolrInputDocument> docs) {if (documents == null) {documents = new LinkedHashMap<>();}for (SolrInputDocument doc : docs) {Objects.requireNonNull(doc, "Cannot add a null SolrInputDocument");documents.put(doc, null);}return this;
}// 按id删除
public UpdateRequest deleteById(String id) {if (deleteById == null) {deleteById = new LinkedHashMap<>();}deleteById.put(id, null);return this;
}// 有参按id删除
public UpdateRequest deleteById(String id, String route, Long version) {if (deleteById == null) {deleteById = new LinkedHashMap<>();}Map<String, Object> params = (route == null && version == null) ? null : new HashMap<>(1);if (version != null)params.put(VER, version);if (route != null)params.put(_ROUTE_, route);deleteById.put(id, params);return this;
}// 多重按id删除
public UpdateRequest deleteById(List<String> ids) {if (deleteById == null) {deleteById = new LinkedHashMap<>();}for (String id : ids) {deleteById.put(id, null);}return this;
}// 将查询的结果删除
public UpdateRequest deleteByQuery(String q) {if (deleteQuery == null) {deleteQuery = new ArrayList<>();}deleteQuery.add(q);return this;
}// ...// 提交
public UpdateResponse commit(SolrClient client, String collection) throws IOException, SolrServerException {if (params == null)params = new ModifiableSolrParams();params.set(UpdateParams.COMMIT, "true");return process(client, collection);
}// ...
// 剩下的是一些额外操作，比如生成路由，转换为XML格式

观察 UpdateRequest 对象的操作，我们可以发现

上面的成员是用来记录操作的键值对和参数

存储的对象是 SolrInputDocument

UpdateRequest类中并没有提到 process() 或 addAction() 等方法，说明在方法的定义在他的父类中。

观察 AbstractUpdateRequest，其构造器：

public abstract class AbstractUpdateRequest extends SolrRequest<UpdateResponse> implements IsUpdateRequest {protected ModifiableSolrParams params;protected int commitWithin = -1;public enum ACTION {COMMIT,OPTIMIZE}public AbstractUpdateRequest(METHOD m, String path) {super(m, path);}
}

发现参数继续向上传递。

这里我们可以发现 setAction 方法：

public AbstractUpdateRequest setAction(ACTION action, boolean waitFlush, boolean waitSearcher, boolean softCommit, int maxSegments ) {if (params == null)params = new ModifiableSolrParams();if( action == ACTION.OPTIMIZE ) {params.set( UpdateParams.OPTIMIZE, "true" );params.set(UpdateParams.MAX_OPTIMIZE_SEGMENTS, maxSegments);}else if( action == ACTION.COMMIT ) {params.set( UpdateParams.COMMIT, "true" );params.set( UpdateParams.SOFT_COMMIT, String.valueOf(softCommit));}params.set( UpdateParams.WAIT_SEARCHER, String.valueOf(waitSearcher));return this;
}

首先，通过观察源码可知 ModifiableSolrParams 是一个封装好的Map对象，键值是<String, String[]>

这个方法主要就是确定我这一次 request 的请求类型是 COMMIT （提交）还是OPTIMIZE （优化） ，并将相关参数加入到 params 中

此外，还有两个方法：

public AbstractUpdateRequest rollback() {if (params == null)params = new ModifiableSolrParams();params.set( UpdateParams.ROLLBACK, "true" );return this;
}public void setParam(String param, String value) {if (params == null)params = new ModifiableSolrParams();params.set(param, value);
}

一个是指出我这次 request 是一次回滚，另外一个是对于提供参数的操作的封装。

看来 process 方法在 SolrRequest 中

观察 SolrRequest ：

public abstract class SolrRequest<T extends SolrResponse> implements Serializable {public final T process(SolrClient client, String collection) throws SolrServerException, IOException {long startNanos = System.nanoTime();T res = createResponse(client);res.setResponse(client.request(this, collection));long endNanos = System.nanoTime();res.setElapsedTime(TimeUnit.NANOSECONDS.toMillis(endNanos - startNanos));return res;}}

其中 createResponse 由其子类实现，返回一个UpdateResponse，是一个存放结果的数据结构，并且 request 方法也是由 SolrClient 的实现类实现。

寻找 SolrClient 的实现类，我们注意到：

public class DelegationTokenHttpSolrClient extends HttpSolrClient {public final static String DELEGATION_TOKEN_PARAM = "delegation";...@Overrideprotected HttpRequestBase createMethod(final SolrRequest request, String collection) throws IOException, SolrServerException {SolrParams params = request.getParams();if (params != null && params.getParams(DELEGATION_TOKEN_PARAM) != null) {throw new IllegalArgumentException(DELEGATION_TOKEN_PARAM + " parameter not supported");}return super.createMethod(request, collection);}@Overridepublic void setQueryParams(Set<String> queryParams) {queryParams = queryParams == null ?Collections.unmodifiableSet(new HashSet<String>(Arrays.asList(DELEGATION_TOKEN_PARAM))): queryParams;if (!queryParams.contains(DELEGATION_TOKEN_PARAM)) {queryParams = new HashSet<String>(queryParams);queryParams.add(DELEGATION_TOKEN_PARAM);queryParams = Collections.unmodifiableSet(queryParams);}super.setQueryParams(queryParams);}}

实现类中实现了 createMethod 和 setQueryParams

而他的父类中 HttpSolrClient 实现了 request 方法：

public class HttpSolrClient extends BaseHttpSolrClient {public NamedList<Object> request(final SolrRequest request, final ResponseParser processor, String collection)throws SolrServerException, IOException {HttpRequestBase method = createMethod(request, collection);setBasicAuthHeader(request, method);if (request.getHeaders() != null) {Map<String, String> headers = request.getHeaders();for (Map.Entry<String, String> entry : headers.entrySet()) {method.setHeader(entry.getKey(), entry.getValue());}}return executeMethod(method, request.getUserPrincipal(), processor, isV2ApiRequest(request));}// ...protected NamedList<Object> executeMethod(HttpRequestBase method, Principal userPrincipal, final ResponseParser processor, final boolean isV2Api) throws SolrServerException {method.addHeader("User-Agent", AGENT);org.apache.http.client.config.RequestConfig.Builder requestConfigBuilder = HttpClientUtil.createDefaultRequestConfigBuilder();if (soTimeout != null) {requestConfigBuilder.setSocketTimeout(soTimeout);}if (connectionTimeout != null) {requestConfigBuilder.setConnectTimeout(connectionTimeout);}if (followRedirects != null) {requestConfigBuilder.setRedirectsEnabled(followRedirects);}method.setConfig(requestConfigBuilder.build());HttpEntity entity = null;InputStream respBody = null;boolean shouldClose = true;try {// Execute the method.HttpClientContext httpClientRequestContext = HttpClientUtil.createNewHttpClientRequestContext();if (userPrincipal != null) {// Normally the context contains a static userToken to enable reuse resources.// However, if a personal Principal object exists, we use that instead, also as a means// to transfer authentication information to Auth plugins that wish to intercept the request laterhttpClientRequestContext.setUserToken(userPrincipal);}final HttpResponse response = httpClient.execute(method, httpClientRequestContext);int httpStatus = response.getStatusLine().getStatusCode();// Read the contentsentity = response.getEntity();respBody = entity.getContent();Header ctHeader = response.getLastHeader("content-type");String contentType;if (ctHeader != null) {contentType = ctHeader.getValue();} else {contentType = "";}// handle some http level checks before trying to parse the responseswitch (httpStatus) {case HttpStatus.SC_OK:case HttpStatus.SC_BAD_REQUEST:case HttpStatus.SC_CONFLICT:  // 409break;case HttpStatus.SC_MOVED_PERMANENTLY:case HttpStatus.SC_MOVED_TEMPORARILY:if (!followRedirects) {throw new SolrServerException("Server at " + getBaseURL()+ " sent back a redirect (" + httpStatus + ").");}break;default:if (processor == null || "".equals(contentType)) {throw new RemoteSolrException(baseUrl, httpStatus, "non ok status: " + httpStatus+ ", message:" + response.getStatusLine().getReasonPhrase(),null);}}if (processor == null || processor instanceof InputStreamResponseParser) {// no processor specified, return raw streamNamedList<Object> rsp = new NamedList<>();rsp.add("stream", respBody);rsp.add("closeableResponse", response);// Only case where stream should not be closedshouldClose = false;return rsp;}String procCt = processor.getContentType();if (procCt != null) {String procMimeType = ContentType.parse(procCt).getMimeType().trim().toLowerCase(Locale.ROOT);String mimeType = ContentType.parse(contentType).getMimeType().trim().toLowerCase(Locale.ROOT);if (!procMimeType.equals(mimeType)) {// unexpected mime typeString msg = "Expected mime type " + procMimeType + " but got " + mimeType + ".";Header encodingHeader = response.getEntity().getContentEncoding();String encoding;if (encodingHeader != null) {encoding = encodingHeader.getValue();} else {encoding = "UTF-8"; // try UTF-8}try {msg = msg + " " + IOUtils.toString(respBody, encoding);} catch (IOException e) {throw new RemoteSolrException(baseUrl, httpStatus, "Could not parse response with encoding " + encoding, e);}throw new RemoteSolrException(baseUrl, httpStatus, msg, null);}}NamedList<Object> rsp = null;String charset = EntityUtils.getContentCharSet(response.getEntity());try {rsp = processor.processResponse(respBody, charset);} catch (Exception e) {throw new RemoteSolrException(baseUrl, httpStatus, e.getMessage(), e);}Object error = rsp == null ? null : rsp.get("error");if (error != null && (isV2Api || String.valueOf(getObjectByPath(error, true, errPath)).endsWith("ExceptionWithErrObject"))) {throw RemoteExecutionException.create(baseUrl, rsp);}if (httpStatus != HttpStatus.SC_OK && !isV2Api) {NamedList<String> metadata = null;String reason = null;try {NamedList err = (NamedList) rsp.get("error");if (err != null) {reason = (String) err.get("msg");if(reason == null) {reason = (String) err.get("trace");}metadata = (NamedList<String>)err.get("metadata");}} catch (Exception ex) {}if (reason == null) {StringBuilder msg = new StringBuilder();msg.append(response.getStatusLine().getReasonPhrase()).append("\n\n").append("request: ").append(method.getURI());reason = java.net.URLDecoder.decode(msg.toString(), UTF_8);}RemoteSolrException rss = new RemoteSolrException(baseUrl, httpStatus, reason, null);if (metadata != null) rss.setMetadata(metadata);throw rss;}return rsp;} catch (ConnectException e) {throw new SolrServerException("Server refused connection at: "+ getBaseURL(), e);} catch (SocketTimeoutException e) {throw new SolrServerException("Timeout occurred while waiting response from server at: "+ getBaseURL(), e);} catch (IOException e) {throw new SolrServerException("IOException occurred when talking to server at: " + getBaseURL(), e);} finally {if (shouldClose) {Utils.consumeFully(entity);}}}
}

封装了网络请求

所以使用 Solr 需要在服务器端部署 Solr 的服务器，然后在客户端需要指出服务器的URL，Solr 会通过访问服务器的方式获取持久化数据。