Solr 二--core 核心源码解读和如何写solr plugin

从web.xml 开始找到web 入口

<?xml version="1.0" encoding="UTF-8"?>
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<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" metadata-complete="true" version="2.5">
<filter>
<filter-name>SolrRequestFilter</filter-name>
<filter-class>org.apache.solr.servlet.SolrDispatchFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>SolrRequestFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>Zookeeper</servlet-name>
<servlet-class>org.apache.solr.servlet.ZookeeperInfoServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>LoadAdminUI</servlet-name>
<servlet-class>org.apache.solr.servlet.LoadAdminUiServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>RedirectOldAdminUI</servlet-name>
<servlet-class>org.apache.solr.servlet.RedirectServlet</servlet-class>
<init-param>
<param-name>destination</param-name>
<param-value>${context}/#/</param-value>
</init-param>
</servlet>
<servlet>
<servlet-name>RedirectOldZookeeper</servlet-name>
<servlet-class>org.apache.solr.servlet.RedirectServlet</servlet-class>
<init-param>
<param-name>destination</param-name>
<param-value>${context}/zookeeper</param-value>
</init-param>
</servlet>
<servlet>
<servlet-name>RedirectLogging</servlet-name>
<servlet-class>org.apache.solr.servlet.RedirectServlet</servlet-class>
<init-param>
<param-name>destination</param-name>
<param-value>${context}/#/~logging</param-value>
</init-param>
</servlet>
<servlet>
<servlet-name>SolrRestApi</servlet-name>
<servlet-class>org.restlet.ext.servlet.ServerServlet</servlet-class>
<init-param>
<param-name>org.restlet.application</param-name>
<param-value>org.apache.solr.rest.SolrRestApi</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>RedirectOldAdminUI</servlet-name>
<url-pattern>/admin/</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>RedirectOldAdminUI</servlet-name>
<url-pattern>/admin</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>RedirectOldZookeeper</servlet-name>
<url-pattern>/zookeeper.jsp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>RedirectLogging</servlet-name>
<url-pattern>/logging</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Zookeeper</servlet-name>
<url-pattern>/zookeeper</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoadAdminUI</servlet-name>
<url-pattern>/admin.html</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>SolrRestApi</servlet-name>
<url-pattern>/schema/*</url-pattern>
</servlet-mapping>
<mime-mapping>
<extension>.xsl</extension>
<mime-type>application/xslt+xml</mime-type>
</mime-mapping>
<welcome-file-list>
<welcome-file>admin.html</welcome-file>
</welcome-file-list>
</web-app><span id="_xhe_cursor">
</span>

web.xml定义了web的入口和url mapping

从web.xml里面可以看到所有的url都会首先经过filter：org.apache.solr.servlet.SolrDispatchFilter

SolrDispatchFilter

1.init(FilterConfig config)做了哪些准备工作

1）从FilterConfig (web.xml)中获取当前pathPrefix，定位solrHome目录

2）加载lib下面的class和依赖的luceneSPI

3）定位solrHome下面的solr.xml,并读取solr.xml相关信息存入ConfigSolr，最重要的是获取zkHost信息

4）接下来load 每个core的信息通过CoreConatiner 类的load方法，其主要包括：

Note：ConfigSolr 在代码中指定了core admin Handler：

org.apache.solr.handler.admin.CoreAdminHandler，该类对应 admin UI的core admin 部分的处理

初始化zookeeper相关的东西，并从zookeeper中获取所有的获取所有solr node的CoreDescription信息（see ZKController）

得到所有cores的信息后，并行load所有的core（通过一个fixed threadPool 实现的）。

这样SolrCores 在CoreContainer中已经初始化，并且通过SolrDispatchFilter中一个volatile的CoreContainer 变量共享

2. DoFilter 接收allServletRequest并分发所有的request到具体的Handler处理

1）讲CoreContainer放入request的attribute中 share

2）解析parth url，并分给相应的Handler处理

3）如果是进入指定的core的话，每个core下层的request则通过SolrCores里面的

RequestHandlers 找到对于的RequestHander处理。

4）SolrQueryParsers 负责将HttpServeletRequest 转化成SolrQueryRequest。

SolrRequestHandler

1.init

其中参数应该是lst部分

<requestHandler name="/query" class="solr.SearchHandler">
<lst name="defaults">
<str name="echoParams">explicit</str>
<str name="wt">json</str>
<str name="indent">true</str>
<str name="df">text</str>
</lst>
</requestHandler>

如果你有一些属性依赖NamedList 或Pluginfo，且必须在servlet接收request前初始化，则可以override父类RequestHandlerBase的init接口

2. HandleRequest

SolrCoreAware

如果你有一些属性依赖SolrCore,且必须在servlet接收request前初始化，可以实现该接口的inform方法，将solrcore注入，类似Spring里面的XXXAware。

SearchHandler

1.只有一个searchHandler，searchhandler里面hold了一个List<SearchComponent>

2.可以通过注入一个新的searchComponent来custom searchHandler。

3.searchComponent可在solrconfig.xml里面查询。

4.http://wiki.apache.org/solr/SearchComponent

Search components enable a
SearchHandler to chain together reusable pieces of functionality to create custom search handlers without writing code.

There are currently several "default"
SearchComponents which now comprise the default SearchHandler. They are:

query -
QueryComponent

facet -
FacetComponent

mlt -
MoreLikeThis

highlight -
Highlighting

stats -
Statistics

Solr1.4

debug -
Debug

SearchComponent

QueryComponent