Nutch在搜索时把自定义的字段（filed）加入检索条件

 1、问题原因分析

错误org.apache.nutch.searcher.QueryException: Not a known field name:publishUrl原因

原因分析：

在NutchBean的main()方法中

final NutchBean bean = new NutchBean(conf);

声明NutchBean 得到一个bean，在他的构造函数中使用LuceneSearchBean()来实现searchBean。

searchBean = new LuceneSearchBean(conf, indexDir, indexesDir);

LuceneSearchBean的构造函数调用自己的init()方法进行初始化。其中searcher的使用IndexSearher()进行实例化。

this.searcher = new IndexSearcher(indexDir, this.conf);

在IndexSearcher的构造函数中调中自己的()方法来初实例化queryFilters

this.queryFilters = new QueryFilters(conf);

QueryFIlters中有三个field

private QueryFilter[] queryFilters; //加载的filter   private HashSet<String> FIELD_NAMES ;   //字段名   private HashSet<String> RAW_FIELD_NAMES;//字段名

默认加载LanguageQueryFilte、DefaultQueryFilter

UrlQueryFilter、SiteQueryFilter四个插件

FIELD_NAMES中的值为[site, , lang, DEFAULT, url]

RAW_FIELD_NAMES中的值为[site, , lang]

在QueryFilter()的构造函数中会将FIELD_NAMES和RAW_FIELD_NAMES存入到ObjectCahche中

FIELD_NAMES.addAll(fieldNames); FIELD_NAMES.addAll(rawFieldNames); objectCache.setObject("FIELD_NAMES", FIELD_NAMES); RAW_FIELD_NAMES.addAll(rawFieldNames); objectCache.setObject("RAW_FIELD_NAMES", RAW_FIELD_NAMES);

 

当执行到 final Hits hits = bean.search(query);时会调用searchBean.search(query);即LuceneSearchBean的方法－》IndexSearcher中的Hits search(Query query)：this.queryFilters.filter(query); －》QueryFiltes中的BooleanQuery filter(Query input)

input的值为：[处理, output, -url:www, -publishUrl:qqq]

public BooleanQuery filter(Query input) throws QueryException {     // first check that all field names are claimed by some plugin     Clause[] clauses = input.getClauses();     for (int i = 0; i < clauses.length; i++) {       Clause c = clauses[i];       if (!isField(c.getField())) //因为自定义字段publishUrl不在 FIELD_NAMES中，所以此处报错。         throw new QueryException("Not a known field name:"+c.getField());     }       // then run each plugin     BooleanQuery output = new BooleanQuery();     for (int i = 0; i < this.queryFilters.length; i++) {       output = this.queryFilters[i].filter(input, output);     }     return output;   }

 

public boolean isField(String name) {     return FIELD_NAMES.contains(name);//判断该字段是否在FIELD—NAMES中   }

2、解决方案

在Nutch中已经实现了 一个CustomFieldQueryFilter()的插件用于将自定义字段名加到QueryFilter中。

首先修改customs-field.xml文件，如下：

<entry key="publishUrl.name">publishUrl</entry>   <entry key="publishUrl.indexed">yes</entry>   <entry key="publishUrl.stored">yes</entry>   <entry key="publishUrl.tokenized">yes</entry>   <entry key="publishUrl.boost">1.0</entry>   <entry key="publishUrl.multi">false</entry>     <entry key="publishTitle.name">publishTitle</entry>   <entry key="publishTitle.indexed">yes</entry>   <entry key="publishTitle.stored">yes</entry>   <entry key="publishTitle.tokenized">yes</entry>   <entry key="publishTitle.boost">1.0</entry>   <entry key="publishTitle.multi">false</entry>

然后修改plugin/query-custom/plugin.xml

把里面的<parameter name="fields" value="publishUrl,publishTitle" />

把value改成你自己的字段名

最后在nutch-default.xml中把query-custom加到plugin.includes中