ibatis 缓存机制初探（转）

一，IBATIS 缓存机制使用

 

1，sqlMapConfig.xml中配置

1.SqlMapConfig.xml中
<
settings
cacheModelsEnabled
=
"true"
 //设置为true
enhancementEnabled
=
"true"
lazyLoadingEnabled
=
"true"
.............
/>

1.SqlMapConfig.xml中
<settings
cacheModelsEnabled="true" //设置为true
enhancementEnabled="true"
lazyLoadingEnabled="true"
.............
/> 

 注意点,k，必须配置settings这个标签，否则

 

cacheModelsEnabled
=
"false"

cacheModelsEnabled="false" 

 

cacheModelsEnabled
=
"true"
  是默认的，无须配置也可，建议配置

cacheModelsEnabled="true"  是默认的，无须配置也可，建议配置

 

2，配置具体的sqlMap.xml

 

<
cacheModel
 
id
=
"baby-cache"
 
type
=
"LRU"
 
readOnly
=
"false"
        serialize
=
"true"
>
        <
flushInterval
 
hours
=
"24"
 
/>
        <
flushOnExecute
 
statement
=
"getBabyByParams"
 
/>
        <
property
 
value
=
"600"
 
name
=
"size"
 
/>
    </
cacheModel
>


<
select
 
id
=
"getBabyByParams"
 
resultMap
=
"baby-Result"
 
cacheModel
=
"baby-cache"
>
        select * from Baby
        <
dynamic
 
prepend
=
"where"
>
            <
isPropertyAvailable
 
property
=
"name"
 
prepend
=
"and"
>
                name
 = #name#
            </
isPropertyAvailable
>
            <
isPropertyAvailable
 
property
=
"sex"
 
prepend
=
"and"
>
                sex
 =
                #sex,jdbcType
=
VARCHAR
,
javaType
=
com
.yajun.enumdemo.SexEnum#
            </
isPropertyAvailable
>
            <
isPropertyAvailable
 
property
=
"BirthdayBondStart"
                prepend
=
"and"
>
               <![CDATA[
                     birthday >= cast(#BirthdayBondStart# as datetime)
               ]]>
            </
isPropertyAvailable
>
            <
isPropertyAvailable
 
property
=
"BirthdayBondEnd"
                prepend
=
"and"
>
                 <![CDATA[
                     birthday <= cast(#BirthdayBondEnd# as datetime)
                 ]]>
            </
isPropertyAvailable
>
            <
isPropertyAvailable
 
property
=
"hobby"
 
prepend
=
"and"
>
                hobby like '%'||#hobby#||'%'
            </
isPropertyAvailable
>
        </
dynamic
>
    </
select
>

<cacheModel id="baby-cache" type="LRU" readOnly="false"
		serialize="true">
		<flushInterval hours="24" />
		<flushOnExecute statement="getBabyByParams" />
		<property value="600" name="size" />
	</cacheModel>


<select id="getBabyByParams" resultMap="baby-Result" cacheModel="baby-cache">
		select * from Baby
		<dynamic prepend="where">
			<isPropertyAvailable property="name" prepend="and">
				name = #name#
		   	</isPropertyAvailable>
			<isPropertyAvailable property="sex" prepend="and">
				sex =
				#sex,jdbcType=VARCHAR,javaType=com.yajun.enumdemo.SexEnum#
			</isPropertyAvailable>
			<isPropertyAvailable property="BirthdayBondStart"
				prepend="and"> 
		   	   <![CDATA[
		   	         birthday >= cast(#BirthdayBondStart# as datetime)
		   	   ]]>
			</isPropertyAvailable>
			<isPropertyAvailable property="BirthdayBondEnd"
				prepend="and">
				 <![CDATA[
				     birthday <= cast(#BirthdayBondEnd# as datetime)
				 ]]>
			</isPropertyAvailable>
			<isPropertyAvailable property="hobby" prepend="and">
				hobby like '%'||#hobby#||'%'
			</isPropertyAvailable>
		</dynamic>
	</select>

 

二，具体配置项

 

id : cacheModel的id.

type : cache的类型. ibatis目前提供了LRU,MEMORY,FIFO,OSCACHE这四种.

•       FIFO: com.ibatis.sqlmap.engine.cache.fifo.FifoCacheController
•       LRU:  com.ibatis.sqlmap.engine.cache.fifo.LruCacheController
•       MEMORY: com.ibatis.sqlmap.engine.cache.fifo.MemoryCacheController
•       OSCACHE: com.ibatis.sqlmap.engine.cache.fifo.OSCacheController

      当然,你也可以自己来实现Cache, 你需要做的是让你的Cache类 implements com.ibatis.sqlmap.engine.cache.CacheController.

readOnly : 是否只读. 默认为true, 只读.

serialize : 是否从Cache中读取同一个对象,还是对象的副本.
           只有在readOnly=false才有效.
   因为Cache是只读的,那么为不同session返回的对象肯定是一个.
   只有在Cache是可读写的时候,才需要为每个session返回对象的副本.

flushInterval : Cache刷新间隔. 可以配置hours,minutes,seconds,milliseconds.
           注: 不是说,间隔时间到了,在Cache的statement会自己刷新,而是说,在间隔时间过了后,下次的查询
   将不会从Cache中直接去值,而会用SQL去查.也就是: 如果,间隔时间过了,还没有Cache对应的statement执行
   的话,那么Cache中就会一直是旧的,不用担心Cache数据是旧的,因为下次的查询将会直接从SQL查询,而非Cache,查询的结果也会去更新Cache的值.

flushOnExecute : 当这些statement被执行了,那么下次的查询将会通过SQL去查,同时用查询结果更新Cache.
           注: 和flushInterval的刷新一样,不是主动刷新,而是由下次查询来触发被动刷新.
               在一个cacheModel中可以指定多个flushOnExecute.

property : 这是针对cacheModel的额外的一些属性配置.不同type的cacheModel将会有自己专有的一些property配置.
          FIFO: <property name="size" value="100" />
          LRU: <property name="cache-size" value="100" />
  MEMORY: <property name="reference-type" value="WEAK" />