solr&lucene3.6.0源码解析（四）

本文要描述的是solr的查询插件，该查询插件目的用于生成Lucene的查询Query，类似于查询条件表达式，与solr查询插件相关UML类图如下：

如果我们强行将上面的类图纳入某种设计模式语言的话，本人姑且将之归入桥接模式(Bridge)吧；QParserPlugin插件的行为依赖于QParser的具体类型

QParserPlugin为抽象类，职责为创建QParser类型对象

package org.apache.solr.search;

import org.apache.solr.common.params.SolrParams;

import org.apache.solr.request.SolrQueryRequest;

import org.apache.solr.util.plugin.NamedListInitializedPlugin;

public abstract class QParserPlugin implements NamedListInitializedPlugin {

  /** internal use - name of the default parser */

  public static String DEFAULT_QTYPE = LuceneQParserPlugin.NAME;

  /** internal use - name to class mappings of builtin parsers */

  public static final Object[] standardPlugins = {

    LuceneQParserPlugin.NAME, LuceneQParserPlugin.class,

    OldLuceneQParserPlugin.NAME, OldLuceneQParserPlugin.class,

    FunctionQParserPlugin.NAME, FunctionQParserPlugin.class,

    PrefixQParserPlugin.NAME, PrefixQParserPlugin.class,

    BoostQParserPlugin.NAME, BoostQParserPlugin.class,

    DisMaxQParserPlugin.NAME, DisMaxQParserPlugin.class,

    ExtendedDismaxQParserPlugin.NAME, ExtendedDismaxQParserPlugin.class,

    FieldQParserPlugin.NAME, FieldQParserPlugin.class,

    RawQParserPlugin.NAME, RawQParserPlugin.class,

    TermQParserPlugin.NAME, TermQParserPlugin.class,

    NestedQParserPlugin.NAME, NestedQParserPlugin.class,

    FunctionRangeQParserPlugin.NAME, FunctionRangeQParserPlugin.class,

    SpatialFilterQParserPlugin.NAME, SpatialFilterQParserPlugin.class,

    SpatialBoxQParserPlugin.NAME, SpatialBoxQParserPlugin.class,

  };

  /** return a {@link QParser} */

  public abstract QParser createParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest req);

}

LuceneQParserPlugin类继承自QParserPlugin抽象类，为Solr3.6.0的默认QParserPlugin插件

/**

 * Parse Solr's variant on the Lucene QueryParser syntax.

 * <br>Other parameters:<ul>

 * <li>q.op - the default operator "OR" or "AND"</li>

 * <li>df - the default field name</li>

 * </ul>

 * <br>Example: <code>{!lucene q.op=AND df=text sort='price asc'}myfield:foo +bar -baz</code>

 */

public class LuceneQParserPlugin extends QParserPlugin {

  public static String NAME = "lucene";

  public void init(NamedList args) {

  }

  @Override

  public QParser createParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest req) {

    return new LuceneQParser(qstr, localParams, params, req);

  }

}

class LuceneQParser extends QParser {

  SolrQueryParser lparser;

  public LuceneQParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest req) {

    super(qstr, localParams, params, req);

  }

  @Override

  public Query parse() throws ParseException {

    String qstr = getString();

    if (qstr == null || qstr.length()==0) return null;

    String defaultField = getParam(CommonParams.DF);

    if (defaultField==null) {

      defaultField = getReq().getSchema().getDefaultSearchFieldName();

    }

    lparser = new SolrQueryParser(this, defaultField);

    // these could either be checked & set here, or in the SolrQueryParser constructor

    String opParam = getParam(QueryParsing.OP);

    if (opParam != null) {

      lparser.setDefaultOperator("AND".equals(opParam) ? QueryParser.Operator.AND : QueryParser.Operator.OR);

    } else {

      // try to get default operator from schema

      QueryParser.Operator operator = getReq().getSchema().getSolrQueryParser(null).getDefaultOperator();

      lparser.setDefaultOperator(null == operator ? QueryParser.Operator.OR : operator);

    }

    return lparser.parse(qstr);

  }

  @Override

  public String[] getDefaultHighlightFields() {

    return lparser == null ? new String[]{} : new String[]{lparser.getField()};

  }

}

}

其中LuceneQParser类为LuceneQParserPlugin类的内部类，继承自QParser抽象类，其职责为创建Lucene的Query对象

QParser抽象类，其中的静态方法getParser获取具体的QParser类型对象供RequestHandler处理器调用

/** Create a <code>QParser</code> to parse <code>qstr</code>,

   * assuming that the default query type is <code>defaultType</code>.

   * The query type may be overridden by local parameters in the query

   * string itself.  For example if defaultType=<code>"dismax"</code>

   * and qstr=<code>foo</code>, then the dismax query parser will be used

   * to parse and construct the query object.  However

   * if qstr=<code>{!prefix f=myfield}foo</code>

   * then the prefix query parser will be used.

   */

  public static QParser getParser(String qstr, String defaultType, SolrQueryRequest req) throws ParseException {

    // SolrParams localParams = QueryParsing.getLocalParams(qstr, req.getParams());

    String stringIncludingLocalParams = qstr;

    SolrParams localParams = null;

    SolrParams globalParams = req.getParams();

    boolean valFollowedParams = true;

    int localParamsEnd = -1;

    if (qstr != null && qstr.startsWith(QueryParsing.LOCALPARAM_START)) {

      Map<String, String> localMap = new HashMap<String, String>();

      localParamsEnd = QueryParsing.parseLocalParams(qstr, 0, localMap, globalParams);

      String val = localMap.get(QueryParsing.V);

      if (val != null) {

        // val was directly specified in localParams via v=<something> or v=$arg

        valFollowedParams = false;

      } else {

        // use the remainder of the string as the value

        valFollowedParams = true;

        val = qstr.substring(localParamsEnd);

        localMap.put(QueryParsing.V, val);

      }

      localParams = new MapSolrParams(localMap);

    }

    String type;

    if (localParams == null) {

      type = defaultType;

    } else {

      type = localParams.get(QueryParsing.TYPE,defaultType);

      qstr = localParams.get("v");

    }

    type = type==null ? QParserPlugin.DEFAULT_QTYPE : type;

    QParserPlugin qplug = req.getCore().getQueryPlugin(type);

    QParser parser =  qplug.createParser(qstr, localParams, req.getParams(), req);

    parser.stringIncludingLocalParams = stringIncludingLocalParams;

    parser.valFollowedParams = valFollowedParams;

    parser.localParamsEnd = localParamsEnd;

    return parser;

  }