最近这些天一直在配置Solr，折腾了好长时间才搞好。感觉有些坑，这里做个笔记记录下来。

首先是Solr的配置文件solrconfig.xml。

<requestHandler name="/dataimport" class="org.apache.solr.handler.dataimport.DataImportHandler">
  <lst name="defaults">
    <str name="config">/path/to/my/DIHconfigfile.xml</str>
  </lst>
</requestHandler>

这里需要修改的地方只有/path/to/my/DIHconfigfile.xml。例如，可以把这个配置文件命名为db-data-config.xml。把这个文件放在同一个目录下，然后我们对其可以进行编辑：

<dataConfig>
<!-- The first element is the dataSource, in this case an HSQLDB database.
     The path to the JDBC driver and the JDBC URL and login credentials are all specified here.
     Other permissible attributes include whether or not to autocommit to Solr, the batchsize
     used in the JDBC connection, a 'readOnly' flag.
     The password attribute is optional if there is no password set for the DB.
-->
  <dataSource driver="org.hsqldb.jdbcDriver" url="jdbc:hsqldb:./example-DIH/hsqldb/ex" user="sa" password="secret"/>
<!--
Alternately the password can be encrypted as follows. This is the value obtained as a result of the command
openssl enc -aes-128-cbc -a -salt -in pwd.txt
password="U2FsdGVkX18QMjY0yfCqlfBMvAB4d3XkwY96L7gfO2o="
WHen the password is encrypted, you must provide an extra attribute
encryptKeyFile="/location/of/encryptionkey"
This file should a text file with a single line containing the encrypt/decrypt password

-->
<!-- A 'document' element follows, containing multiple 'entity' elements.
     Note that 'entity' elements can be nested, and this allows the entity
     relationships in the sample database to be mirrored here, so that we can
     generate a denormalized Solr record which may include multiple features
     for one item, for instance -->
  <document>

<!-- The possible attributes for the entity element are described below.
     Entity elements may contain one or more 'field' elements, which map
     the data source field names to Solr fields, and optionally specify
     per-field transformations -->
<!-- this entity is the 'root' entity. -->
    <entity name="item" query="select * from item"
            deltaQuery="select id from item where last_modified > '${dataimporter.last_index_time}'">
      <field column="NAME" name="name" />

<!-- This entity is nested and reflects the one-to-many relationship between an item and its multiple features.
     Note the use of variables; ${item.ID} is the value of the column 'ID' for the current item
     ('item' referring to the entity name)  -->
      <entity name="feature"
              query="select DESCRIPTION from FEATURE where ITEM_ID='${item.ID}'"
              deltaQuery="select ITEM_ID from FEATURE where last_modified > '${dataimporter.last_index_time}'"
              parentDeltaQuery="select ID from item where ID=${feature.ITEM_ID}">
        <field name="features" column="DESCRIPTION" />
      </entity>
      <entity name="item_category"
              query="select CATEGORY_ID from item_category where ITEM_ID='${item.ID}'"
              deltaQuery="select ITEM_ID, CATEGORY_ID from item_category where last_modified > '${dataimporter.last_index_time}'"
              parentDeltaQuery="select ID from item where ID=${item_category.ITEM_ID}">
        <entity name="category"
                query="select DESCRIPTION from category where ID = '${item_category.CATEGORY_ID}'"
                deltaQuery="select ID from category where last_modified > '${dataimporter.last_index_time}'"
                parentDeltaQuery="select ITEM_ID, CATEGORY_ID from item_category where CATEGORY_ID=${category.ID}">
          <field column="description" name="cat" />
        </entity>
      </entity>
    </entity>
  </document>
</dataConfig>

这里给出的是官方wiki的配置。在实战中，比如我们的SQL用的是mySQL，那么我们需要进行一些修改。 注意，这里有一个UniqueID，必要时进行修改。