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;
}
SolrQueryParser继承自Lucene的QueryParser，职责为解析查询表达式，生成查询Query对象（重写了父类QueryParser的部分方法）
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本系列solr&lucene3.6.0源码解析系本人原创
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