开源，从关注产品社区做起（ibatis3.x的最近一个issue展示）-优快云博客

题记：

“低碳从拔下插头做起”，开源，从关注产品社区做起：）

发这个贴的的缘由是看了jnn大哥发的一篇关于开源软件的帖子http://www.iteye.com/topic/277696，虽然是08年写的，但里面说到follow社区的mail list的建议是不错的，想想自己还未奉献过代码，于是去ibaits的google社区瞅了一眼，其实只要你行动，提交一个被accepted的issue并不是那么困难。

以下就是展现一个最新被ibatis3.x接受的建议。（当然不是我commit的，希望以后有机会吧）

Reported by clinton.begin, May 17, 2010
Reporter: Travis Hein

Would it be possible to create a new annotation (or does one exist already
and I just have not found it yet), where I can specify that @Select results
should be a <resultMap> that exists in the mapper XML file ?

可以不可以为@select新增一个注解用于重用resultMap配置中定义的map。

For example,

比如：

Consider a "country" table,

CREATE TABLE COUNTRY
(
   ID bigint PRIMARY KEY NOT NULL,
   CODE varchar(2) NOT NULL,
   ISO_CODE varchar(3) NOT NULL,
   NAME varchar(2147483647),
   COUNTRY_CODE varchar(10),
   ACTIVE boolean DEFAULT TRUE NOT NULL
);

And the java Bean,

public class Country {
  Long id;
  String code; // 2 digit ISO country code
  String isoCode; // 3 digit ISO country code
  String name; // string name
  String countryCode; // the telephone dialing prefix (e.g. +1)
  boolean active = true;

  // and all the get() set() methods for these bean properties
}

And then the mapper interface,

public interface CountryDAO {

  /**
  * Selects all country entries.
  * Though it appears when we use the annotations, we need to specify the
results every time ?
  */
  @Select( value = { "select * from country where active = true" })
  @Results(value = {
      @Result(property="id"),
      @Result(property="code"),
      @Result(property="isoCode", column="iso_code"),
      @Result(property="name", column="name"),
      @Result(property="countryCode", column="country_code"),
      @Result(property="active", column="active")
  })
  List<Country> getAllActive();

  // TODO: all these methods would also be select queries, where I would
want the same results map as above
  Country getById(Long id);
  Country getByCode(String code);
  Country getByIsoCode(String isoCode);
}

这里每个方法都需要重复添加如上返回的map定义，就显的很冗余了。
Where, instead of the @Results annotation, which would need to be
duplicated with its nested @Result annotations on every select method that
I want to return the same mapping, what I would wish to have would be
something like a

@ResultMap(value="myMapperID") 作者想添加这个注解，替代上面的重复定义。

annotation, where the myMapperID would be the ID of a <resultMap> I have
declared in the mapper's xml file that will be included by the
SqlMapConfig.xml (which I have anyway to bind to this mapper interface, and
also because I have some more complex queries declared in the xml mapper
file too).

Where in this example, I already have a

<mapper namespace="CountryDAO">

<resultMap type="Country" id="countryResult">
<result property="id" column="id"/>
<result property="code" column="code"/>
<result property="isoCode" column="iso_code"/>
<result property="name" column="name"/>
<result property="countryCode" column="country_code"/>
<result property="active" column="active"/>
</resultMap>

So this wishful @ResultMap annotation would then make the mapper interface
look like:

修改后的代码变为：

public interface CountryDAO {

  @Select( value = { "select * from country where active = true" })
  @ResultMap(value = "countryResult")
  List<Country> getAllActive();


  // and now other things that want to select into this map can do so,
re-using the single map declaration
  // that is referenced in the xml.

  @Select( value = { "select * from country where id = #{id} })
  @ResultMap(value = "countryResult")
  Country getById(Long id);


  @Select( value = { "select * from country where code = #{code} })
  @ResultMap(value = "countryResult")
  Country getByCode(String code);

  @Select( value = { "select * from country where isoCode = #{isoCode} })
  @ResultMap(value = "countryResult")
  Country getByIsoCode(String isoCode);
}

I think having something like this @ResultMap annotation would be a good
thing to have, what do you think?

看到countryResult这个map已经在xml文件中定义好了，无需再每个方法前面重复定义了，只要声明就ok了。