Java heap dump OQL samples - where

where 可以包含:

=, <=, >, <, [ NOT ] LIKE, [ NOT ] IN, IMPLEMENTS (relational operations)
AND OR != , =

字段可以 [<alias>. ] <field> . <field>. <field>

- SELECT * FROM java.net.URL u where u.port = 443
- SELECT * FROM java.net.URL u where toString(u.host) = "api.google.com"
- SELECT * FROM java.net.URL u where u.@displayName like ".*api.google.com.*"
- SELECT * FROM "com.tianxiaohui.*" u where toString(u) like ".*Metrics.*"  //正则
- SELECT s.address.holder.hostName.toString(), s.timeout FROM java.net.SocksSocketImpl s WHERE (s.port = 443) //socket 的地址和 timeout 时间
- SELECT toString(u.string) FROM java.net.URI u WHERE (toString(u.schemeSpecificPart) LIKE ".+google.com.+")
- SELECT x.capacity FROM java.nio.DirectByteBuffer x WHERE ((toString(x.att) = "null") and (toString(x.cleaner) != "null") and (x.capacity >= (1024 * 1024)))
- SELECT DISTINCT objects x.this$0 FROM java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask x 
- SELECT distinct objects x FROM java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask x WHERE (x.this$0.toString() LIKE ".+0x468369b50")
- SELECT * FROM INSTANCEOF java.lang.Object t WHERE (toHex(t.@objectAddress) >= "0xfbd4c000" AND toHex(t.@objectAddress) <= "0xfce94050") //一段地址空间中的所有对象
- select * from java.nio.DirectByteBuffer x where x.capacity > 65535 and x.cleaner != null
- SELECT o.toString() FROM OBJECTS ( SELECT OBJECTS outbounds(t) FROM org.apache.tomcat.util.threads.TaskThread t WHERE (t.toString() = "DefaultThreadPool-23") ) o WHERE (o.toString() LIKE ".+TracingInfoImpl.+")

如何在MAT里使用OQL 做到group by - count的效果?
使用OQL之后, 在OQL的Tab 里, 可以看到菜单栏有个 导出 的Icon, 可以导出为HTMl, CSV, TXT. 导出CSV,使用Excel做count.

如果 0x789342b78 对应的地址是一个类class(不是instance), 那么可以用下面这种查法:
select * from 0x789342b78

如果要查询某个 Class 的 static 字段里面的数据:

SELECT * FROM java.lang.Class x where x.toString() LIKE ".+com.tianxiaohui.platform.config.impl.ConfigProvider.*"

如果要查询一个抽象类的具体实现:

select * from INSTANCEOF java.net.AbstractPlainSocketImpl

Java JDBC 相关的

# 一个连接有多少 open 的 ResultSet
SELECT * FROM oracle.jdbc.driver.OracleResultSetImpl rs WHERE (rs.connection.toString() LIKE ".+0x7a3af6cf8")

内置函数:

1. toHex( number ) //转换数字为16进制
2. toString( object ) //转换对象为 String
3. dominators( object ) //被这个对象直接控制的
4. dominatorof( object ) //这个对象被那些对象直接控制
5. outbounds( object ) //
6. inbounds( object ) //
7. classof( object ) // 当前对象的类

如何查看一个对象的 dominator, 然后就可以用 dominatorof() 函数: