一周前，MyBatis和Apache ignite 宣布支持apache ignite作为MyBatis缓存（L2缓存）。

从技术上讲，MyBatis支持两个级别的缓存：

1. 本地缓存，默认情况下始终启用
2. L2缓存，可选

随着Apache Ignite项目的各种功能Swift发展，在本博文中，我们将详细研究MyBatis支持。

第二级缓存存储实体数据，但不存储实体或对象本身。 数据以“序列化”格式存储，看起来像哈希图，其中键是实体ID，而值是原始值列表。

这是一个示例，其缓存条目在Apache ignite中的样子：

哪里：

• 快取金钥 ：

  CacheKey [idHash=1499858, hash=2019660929, checksum=800710994, count=6, multiplier=37, hashcode=2019660929, updateList=[com.blu.ignite.mapper.UserMapper.getUserObject, 0, 2147483647, SELECT * FROM all_objects t where t.OBJECT_TYPE='TABLE' and t.object_name=?, USERS, SqlSessionFactoryBean]]

• 值类别 ： java.util.ArrayList
• 缓存值 ：

  [UserObject [idHash=243119413, hash=1658511469, owner=C##DONOTDELETE, object_type=TABLE, object_id=94087, created=Mon Feb 15 13:59:41 MSK 2016, object_name=USERS]]

对于示例，我从Oracle数据库中选择了“ all_objects”对象和以下查询

SELECT count(*) FROM all_objects;SELECT * FROM all_objects t where t.OBJECT_TYPE='TABLE' and t.object_name='EMP';SELECT * FROM all_objects t where t.OBJECT_TYPE='TABLE';

就我而言，给定的查询执行时间平均约为660毫秒。

SELECT count(*) FROM all_objects;

接下来的下一个查询执行时间超过700ms：

SELECT t.object_type, count(*) FROM all_objects t group by t.OBJECT_TYPE;

让我们添加apache ignite作为第二级缓存并检查结果。 如果您想知道如何使用spring和myBatis安装和配置apache ignite，请参阅我以前的博客文章 。 此外，您可以在github存储库中找到所有源代码。

首先，让我们在项目中添加myBatis maven依赖项。

<dependency><groupId>org.mybatis.caches</groupId><artifactId>mybatis-ignite</artifactId><version>1.0.0-beta1</version>
</dependency>

然后，只需在映射器XML中指定它，如下所示

<mapper namespace="com.blu.ignite.mapper.UserMapper"><cache type="org.mybatis.caches.ignite.IgniteCacheAdapter" /><select id="getUserObject" parameterType="String" resultType="com.blu.ignite.dto.UserObject" useCache="true">SELECT * FROM all_objects t where t.OBJECT_TYPE='TABLE' and t.object_name=#{objectName}</select><select id="getAllObjectsTypeByGroup" parameterType="String" resultType="com.blu.ignite.dto.UobjectGroupBy" useCache="true">SELECT t.object_type, count(*) as cnt FROM all_objects t group by t.OBJECT_TYPE</select><select id="allObjectCount" parameterType="String" resultType="String" useCache="true">SELECT count(*) FROM all_objects</select>
</mapper>

我也有以下的Java映射器：

public interface UserMapper {User getUser( String id);List getUniqueJob();UserObject getUserObject(String objectName);String allObjectCount();List getAllObjectsTypeByGroup();
}

和Web服务，如下所示：

@WebService(name = "BusinessRulesServices",serviceName="BusinessRulesServices",targetNamespace = "http://com.blu.rules/services")
public class WebServices {private UserServices userServices;@WebMethod(operationName = "getUserName")public String getUserName(String userId){User user = userServices.getUser(userId);return user.getuName();}@WebMethod(operationName = "getUserObject")public UserObject getUserObject(String objectName){return userServices.getUserObject(objectName);}@WebMethod(operationName = "getUniqueJobs")public List getUniqueJobs(){return userServices.getUniqueJobs();}@WebMethod(exclude = true)public void setDao(UserServices userServices){this.userServices = userServices;}@WebMethod(operationName = "allObjectCount")public String allObjectCount(){return userServices.allObjectCount();}@WebMethod(operationName = "getAllObjectsTypeCntByGroup")public List getAllObjectsTypeCntByGroup(){return userServices.getAllObjectCntbyGroup();}}

如果我将在soupUI中调用Web方法'getAllObjectsTypeCntByGroup'，则第一次它将获得非常高的响应时间，大约为1700 ms，因为结果不在缓存中。 从第二次开始，响应时间将为〜4到〜5 ms。

首次调用网络方法如下所示：

第二次或更晚调用Web方法的响应时间

在apache中，ignite缓存条目将如下所示：

• 快取金钥 ：

  CacheKey [idHash=46158416, hash=1558187086, checksum=2921583030, count=5, multiplier=37, hashcode=1558187086, updateList=[com.blu.ignite.mapper.UserMapper.getAllObjectsTypeByGroup, 0, 2147483647, SELECT t.object_type, count(*) as cnt FROM all_objects t group by t.OBJECT_TYPE, SqlSessionFactoryBean]]

• 值类别 ： java.util.ArrayList
• 缓存值 ：

  [UobjectGroupBy [idHash=2103707742, hash=1378996400, cnt=1, object_type=EDITION], UobjectGroupBy [idHash=333378159, hash=872886462, cnt=444, object_type=INDEX PARTITION], UobjectGroupBy [idHash=756814918, hash=1462794064, cnt=32, object_type=TABLE SUBPARTITION], UobjectGroupBy [idHash=931078572, hash=953621437, cnt=2, object_type=CONSUMER GROUP], UobjectGroupBy [idHash=1778706917, hash=1681913927, cnt=256, object_type=SEQUENCE], UobjectGroupBy [idHash=246231872, hash=1764800190, cnt=519, object_type=TABLE PARTITION], UobjectGroupBy [idHash=1138665719, hash=1030673983, cnt=4, object_type=SCHEDULE], UobjectGroupBy [idHash=232948577, hash=1038362844, cnt=1, object_type=RULE], UobjectGroupBy [idHash=1080301817, hash=646054631, cnt=310, object_type=JAVA DATA], UobjectGroupBy [idHash=657724550, hash=1248576975, cnt=201, object_type=PROCEDURE], UobjectGroupBy [idHash=295410055, hash=33504659, cnt=54, object_type=OPERATOR], UobjectGroupBy [idHash=150727006, hash=499210168, cnt=2, object_type=DESTINATION], UobjectGroupBy [idHash=1865360077, hash=727903197, cnt=9, object_type=WINDOW], UobjectGroupBy [idHash=582342926, hash=1060308675, cnt=4, object_type=SCHEDULER GROUP], UobjectGroupBy [idHash=1968399647, hash=1205380883, cnt=1306, object_type=PACKAGE], UobjectGroupBy [idHash=1495061270, hash=1345537223, cnt=1245, object_type=PACKAGE BODY], UobjectGroupBy [idHash=1328790450, hash=1823695135, cnt=228, object_type=LIBRARY], UobjectGroupBy [idHash=1128429299, hash=1267824468, cnt=10, object_type=PROGRAM], UobjectGroupBy [idHash=760711193, hash=1240703242, cnt=17, object_type=RULE SET], UobjectGroupBy [idHash=317487814, hash=61657487, cnt=10, object_type=CONTEXT], UobjectGroupBy [idHash=1079028994, hash=1960895356, cnt=229, object_type=TYPE BODY], UobjectGroupBy [idHash=276147733, hash=873140579, cnt=44, object_type=XML SCHEMA], UobjectGroupBy [idHash=24378178, hash=1621363993, cnt=1014, object_type=JAVA RESOURCE], UobjectGroupBy [idHash=1891142624, hash=90282027, cnt=10, object_type=DIRECTORY], UobjectGroupBy [idHash=902107208, hash=1995006200, cnt=593, object_type=TRIGGER], UobjectGroupBy [idHash=142411235, hash=444983119, cnt=14, object_type=JOB CLASS], UobjectGroupBy [idHash=373966405, hash=1518992835, cnt=3494, object_type=INDEX], UobjectGroupBy [idHash=580466919, hash=1394644601, cnt=2422, object_type=TABLE], UobjectGroupBy [idHash=1061370796, hash=1861472837, cnt=37082, object_type=SYNONYM], UobjectGroupBy [idHash=1609659322, hash=1543110475, cnt=6487, object_type=VIEW], UobjectGroupBy [idHash=458063471, hash=1317758482, cnt=346, object_type=FUNCTION], UobjectGroupBy [idHash=1886921697, hash=424653540, cnt=7, object_type=INDEXTYPE], UobjectGroupBy [idHash=1455482905, hash=1776171634, cnt=30816, object_type=JAVA CLASS], UobjectGroupBy [idHash=49819096, hash=2110362533, cnt=2, object_type=JAVA SOURCE], UobjectGroupBy [idHash=1916179950, hash=1760023032, cnt=10, object_type=CLUSTER], UobjectGroupBy [idHash=1138808674, hash=215713426, cnt=2536, object_type=TYPE], UobjectGroupBy [idHash=305229607, hash=340664529, cnt=23, object_type=JOB], UobjectGroupBy [idHash=1365509716, hash=623631686, cnt=12, object_type=EVALUATION CONTEXT]]

结论

使用L2缓存可以减少昂贵的数据库操作，在MyBatis中正确使用L2缓存可以将应用程序性能提高10到20倍。 内存数据网格中的Apache Ignite非常适合用于此目的，当然您也可以使用Hazelcash，EhCache或任何其他缓存工具。

翻译自: https://www.javacodegeeks.com/2016/03/pitfalls-mybatis-caches-apache-ignite.html