持之以恒

關于com.ibatis.sqlmap.client.SqlMapExecutor下的insert (java.lang.String id, java.lang.Object parameterObject) 方法，ibatis的api文檔是這樣寫的解釋的：

Java代碼
Executes a mapped SQL INSERT statement. Insert is a bit different from other update methods, as it provides facilities for returning the primary key of the newly inserted row (rather than the effected rows). This functionality is of course optional.

The parameter object is generally used to supply the input data for the INSERT values.

Parameters:
id - The name of the statement to execute.
parameterObject - The parameter object (e.g. JavaBean, Map, XML etc.).
Returns:
The primary key of the newly inserted row. This might be automatically generated by the RDBMS, or selected from a sequence table or other source.
Throws:
java.sql.SQLException - If an error occurs.

Executes a mapped SQL INSERT statement. Insert is a bit different from other update methods, as it provides facilities for returning the primary key of the newly inserted row (rather than the effected rows). This functionality is of course optional.

The parameter object is generally used to supply the input data for the INSERT values.

Parameters:
id - The name of the statement to execute.
parameterObject - The parameter object (e.g. JavaBean, Map, XML etc.).
Returns:
The primary key of the newly inserted row. This might be automatically generated by the RDBMS, or selected from a sequence table or other source.
Throws:
java.sql.SQLException - If an error occurs.


它的意思是說返回值是新插入記錄的主鍵，類型為Object主要是因為主鍵類型可以是int也可以是String類型。

然而，如果我們使用下列的配置文件進行插入的話，返回的值為null

Xml代碼
<insert id="insertPrdcategory" parameterClass="Prdcategory">
insert into Prdcategory ( name,pid,deep ) values ( #name#,
#pid#, #deep# )
</insert>

<insert id="insertPrdcategory" parameterClass="Prdcategory">
insert into Prdcategory ( name,pid,deep ) values ( #name#,
#pid#, #deep# )
</insert>

那我們要怎樣解決這個問題，讓它返回插入行的主鍵呢，這時我們就是使用到<selectKey>,下面僅以MSSQL數據庫為例，改寫上述配置文件，具體如下：



Xml代碼
<insert id="insertPrdcategory" parameterClass="Prdcategory">
insert into Prdcategory ( name,pid,deep ) values ( #name#,
#pid#, #deep# )
<selectKey resultClass="int" keyProperty="id">
select max(id) from Prdcategory
</selectKey>
</insert>

<insert id="insertPrdcategory" parameterClass="Prdcategory">
insert into Prdcategory ( name,pid,deep ) values ( #name#,
#pid#, #deep# )
<selectKey resultClass="int" keyProperty="id">
select max(id) from Prdcategory
</selectKey>
</insert>


DAO的實現類方法里面就應該這樣寫了（注意整型轉換用Integer類名）

Java代碼
public int insertPrdcategory(Prdcategory product) throws Exception {
return (Integer)IbatisUtil.getSqlMapper().insert("insertPrdcategory", product);
}

public int insertPrdcategory(Prdcategory product) throws Exception {
return (Integer)IbatisUtil.getSqlMapper().insert("insertPrdcategory", product);
}


這樣就算是OK了。


小白