云计算的二十个基本定义 不可不知！

1.Map作为parameterClass

映射文件：

<!--use Map type as parameterClass-->
<select id="getProduct-Map" parameterClass="java.util.Map" resultMap="get-product-result">
<![CDATA[
select * from t_product
where prd_id=#id# and prd_description=#description#
]]>
</select>

 DAO层：

/**
* java.util.Map作为parameterClass
*/
public Product getProductMap(Map map) throws SQLException {
init();
Product product = (Product)sqlMapClient.queryForObject("getProduct-Map", map);
return product;
}

 Test类：

public void getProductMap() throws SQLException{
Map map = new HashMap();
map.put("id", new Integer(1));
map.put("description", "basketball");
Product product = productDao.getProductMap(map);
System.out.println(product);
}

 结果：

id:1

description:basketball

price206.99

 

 

2.Map作为resultClass

映射文件：

<resultMap id="get-product-map" class="java.util.HashMap">
<result property="id" column="prd_id"/>
<result property="description" column="prd_description"/>
<result property="price" column="prd_price"/>
</resultMap>

<!--START  use Map type as resultClass,MUST use java.util.HashMap instead java.util.Map-->
<select id="getProdcut-MapResult" resultClass="java.util.HashMap
">
<![CDATA[
select * from t_product
]]>
</select>

<select id="getProductUseMap-resultMap" resultMap="get-product-map">
<![CDATA[
select * from t_product
]]>
</select>
<!-- END  -->

 DAO层：

/**
* java.util.Map作为resultClass
*/
public List getProductMapResult() throws SQLException {
init();
List list = sqlMapClient.queryForList("getProdcut-MapResult");
return list;

}

public List getProductUseMapByResultMap() throws SQLException {
init();
List list = sqlMapClient.queryForList("getProductUseMap-resultMap");
return list;
}

 Test类：

public void getProductMapResult() throws SQLException{
Map map = null;
List list = productDao.getProductMapResult();
for(Iterator it=list.iterator(); it.hasNext();) {
//List里存放的是java.util.Map类型
Object obj = (Object)it.next();
System.out.println(obj.getClass());
System.out.println(obj);
}
}

public void getProductUseMapByResultMap() throws SQLException {
Map map = null;
List list = productDao.getProductUseMapByResultMap();
for(Iterator it=list.iterator(); it.hasNext();) {
//List里存放的是java.util.Map类型
Object obj = (Object)it.next();
System.out.println(obj.getClass());
System.out.println(obj);
}
}

 
结果：

class java.util.HashMap

{prd_id=1, prd_price=206.99, prd_description=basketball}

class java.util.HashMap

{prd_id=2, prd_price=106.99, prd_description=football}

class java.util.HashMap

{price=206.99, description=basketball, id=1}

class java.util.HashMap

{price=106.99, description=football, id=2}

 

 

注意：

Map作为resultClass时，必须指定具体的实现类，比如java.util.HashMap,否则会报错

Caused by: java.lang.RuntimeException: JavaBeansDataExchange could not instantiate result class.  Cause: java.lang.InstantiationException: java.util.Map