本文要解决的问题:细粒度控制mybatis的二级缓存。mybatis的二级缓存的问题:当更新SQL执行时只清除当前SQL所在命名空间(namespace)的缓存。如果存在2个命名空间namespaceA和namespaceB,当namespaceA下执行更新操作时,namespaceB的缓存并不会清除。正常的情况下,这种策略是不会有问题。但是,如果存在关联查询时就有可能出现问题了,例如namespaceA关联namespaceB,当namespaceB执行更新时清除namespaceB的缓存,这是查询namespaceA时,会导致查询出来的结果是缓存的,即数据不是最新的。步骤如下:
1. 开启mybatis二级缓存
-
<settings>
<setting name="cacheEnabled" value="true" />
</settings>2. 加入SQL分析的jar依赖
<dependency>
<groupId>com.github.jsqlparser</groupId>
<artifactId>jsqlparser</artifactId>
<version>0.9.4</version>
</dependency>3. 复制如下拦截器代码
package com.xyz.core.inctercepter; import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties; import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory; import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.parser.CCJSqlParserUtil;
import net.sf.jsqlparser.statement.Statement;
import net.sf.jsqlparser.statement.delete.Delete;
import net.sf.jsqlparser.statement.insert.Insert;
import net.sf.jsqlparser.statement.select.Select;
import net.sf.jsqlparser.statement.update.Update;
import net.sf.jsqlparser.util.TablesNamesFinder; /**
* 缓存控制拦截器
*
* @author lee
* @since 2016年3月17日
*/
@Intercepts({
@Signature(method = "query", type = Executor.class, args = { MappedStatement.class, Object.class,
RowBounds.class, ResultHandler.class }),
@Signature(method = "update", type = Executor.class, args = { MappedStatement.class, Object.class }) })
public class CachingInterceptor implements Interceptor {
private final static Logger logger = LoggerFactory.getLogger(CachingInterceptor.class);
/**
* 表名关联的命名空间<br/>
* 一个table下关联的namespace
*/
private final static Map<String, Map<String, String>> tableLinks = new HashMap<String, Map<String, String>>(); /**
* 记录已经解析过的SQL,确保一条SQL只被解析一次,提高效率
*/
private final static Map<String, String> dealedMap = new HashMap<String, String>(); public Object intercept(Invocation invocation) throws Throwable {
Object[] args = invocation.getArgs();
MappedStatement ms = (MappedStatement) args[0];
BoundSql boundSql = ms.getBoundSql(args[1]);
if (!ms.getConfiguration().isCacheEnabled() || ms.getCache() == null)
return invocation.proceed();
if (dealedMap.containsKey(ms.getId()) && dealedMap.get(ms.getId()).equals(boundSql.getSql())) {
return invocation.proceed();
}
dealedMap.put(ms.getId(), boundSql.getSql()); final String operate = invocation.getMethod().getName();
final List<String> tableNames = getTableList(boundSql.getSql());
final String namespace = ms.getCache().getId();
logger.debug("当前操作SQL中包含的namespace:" + namespace);
if ("query".equals(operate)) {
deal(namespace, tableNames);
} else {
Configuration configuration = ms.getConfiguration();
clearCache(tableNames, configuration.getMappedStatements());
} return invocation.proceed();
} public Object plugin(Object target) {
return Plugin.wrap(target, this);
} public void setProperties(Properties properties) {
} /**
* 一个namespace包含多个SQL<br/>
* 一条SQL语句包含多个table
*
* @param namespace
* @param tableNames
*/
private void deal(final String namespace, final List<String> tableNames) {
if (tableNames == null || tableNames.size() == 0)
return; for (String tableName : tableNames) {
Map<String, String> namespaces = tableLinks.get(tableName);
if (namespaces == null) {
namespaces = new HashMap<String, String>();
namespaces.put(namespace, namespace);
tableLinks.put(tableName, namespaces);
} else if (!namespaces.containsKey(namespace)) {
namespaces.put(namespace, namespace);
}
}
} /**
* 清除缓存
*
* @param mappedStatments
*/
@SuppressWarnings("rawtypes")
private void clearCache(List<String> tableNames, Collection mappedStatments) {
if (tableNames == null || tableNames.isEmpty())
return;
for (String tableName : tableNames) {
Map<String, String> namespaces = tableLinks.get(tableName);
if (namespaces == null)
continue;
for (String namespaceNeedClearKey : namespaces.keySet()) {
for (Object o : mappedStatments) {
if (o instanceof MappedStatement) {
MappedStatement sta = ((MappedStatement) o);
final String namespace = sta.getCache().getId();
if (namespaceNeedClearKey.equals(namespace)) {
logger.debug("命名空间[{}]的缓存被清除", namespace);
sta.getCache().clear();
break;
}
}
}
}
}
} /**
* 解析SQL中包含的表名
*
* @param sql
* @return
*/
public List<String> getTableList(final String sql) {
try {
Statement statement = CCJSqlParserUtil.parse(sql);
TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();
List<String> tableList = null;
if (statement instanceof Select) {
Select selectStatement = (Select) statement;
tableList = tablesNamesFinder.getTableList(selectStatement);
} else if (statement instanceof Update) {
Update updateStatement = (Update) statement;
tableList = tablesNamesFinder.getTableList(updateStatement);
} else if (statement instanceof Insert) {
Insert insertStatement = (Insert) statement;
tableList = tablesNamesFinder.getTableList(insertStatement);
} else if (statement instanceof Delete) {
Delete deleteStatement = (Delete) statement;
tableList = tablesNamesFinder.getTableList(deleteStatement);
}
logger.debug("SQL:{}中包含的表名:" + tableList, sql);
return tableList;
} catch (JSQLParserException e) {
logger.error("解析sql异常:" + sql, e);
}
return null;
}
}4. 配置mybatis拦截器
<plugins>
<plugin interceptor="com.xyz.core.inctercepter.CachingInterceptor" />
</plugins>