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我们一直在使用 bone cp 进行池化。我们通过 mat 结果注意到它指向这个 com.mysql.jdbc.JDBC4Connection 并且内存使用量不断增加?下面是 2 个示例,我们可以看到内存使用量的增加。

样品 1

21 instances of "com.mysql.jdbc.JDBC4Connection", loaded by "sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0" occupy 11,793,200 (76.19%) bytes. 

Biggest instances:

•com.mysql.jdbc.JDBC4Connection @ 0xf016d728 - 958,096 (6.19%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0094478 - 875,568 (5.66%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0201ba0 - 816,048 (5.27%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04ab3f0 - 754,016 (4.87%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf006ee40 - 727,024 (4.70%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0076a90 - 663,872 (4.29%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04ad490 - 618,200 (3.99%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf00b7bd0 - 616,608 (3.98%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0467bc0 - 612,544 (3.96%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf015fcf0 - 598,400 (3.87%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf021c830 - 584,992 (3.78%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0097818 - 561,224 (3.63%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf01a27c0 - 531,816 (3.44%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf00bea28 - 531,416 (3.43%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf01c2d80 - 522,184 (3.37%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04693e0 - 482,992 (3.12%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf012b158 - 453,256 (2.93%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf147f438 - 424,656 (2.74%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf15ff7d0 - 187,008 (1.21%) bytes. 


Keywords
com.mysql.jdbc.JDBC4Connection
sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0
 Reference Pattern
Class Name Shallow Heap Retained Heap Percentage 
class java.lang.Thread @ 0xf0003840 40 208 0.00 

样品 2

21 instances of "com.mysql.jdbc.JDBC4Connection", loaded by "sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0" occupy 17,339,632 (80.79%) bytes. 

Biggest instances:

•com.mysql.jdbc.JDBC4Connection @ 0xf016d728 - 1,228,048 (5.72%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0094478 - 1,144,056 (5.33%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0201ba0 - 1,126,120 (5.25%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04ab3f0 - 1,074,552 (5.01%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf006ee40 - 993,912 (4.63%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0076a90 - 931,512 (4.34%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf015fcf0 - 930,952 (4.34%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04ad490 - 918,176 (4.28%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf00bea28 - 874,512 (4.07%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0467bc0 - 846,368 (3.94%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf00b7bd0 - 838,448 (3.91%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf021c830 - 799,184 (3.72%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf0097818 - 791,256 (3.69%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf01a27c0 - 763,264 (3.56%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf01c2d80 - 745,088 (3.47%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf012b158 - 710,704 (3.31%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf04693e0 - 704,072 (3.28%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf147f438 - 680,400 (3.17%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf1603618 - 458,472 (2.14%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf148fd70 - 390,984 (1.82%) bytes. 
•com.mysql.jdbc.JDBC4Connection @ 0xf15ff7d0 - 389,552 (1.82%) bytes. 


Keywords
com.mysql.jdbc.JDBC4Connection
sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0
 Reference Pattern
Class Name Shallow Heap Retained Heap Percentage 
class java.lang.Thread @ 0xf0003840 40 208 0.00% 

样本浅层和保留堆

Class Name                                                       |   Objects | Shallow Heap | Retained Heap
------------------------------------------------------------------------------------------------------------
                                                                 |           |              |              
byte[]                                                           |    19,197 |    4,502,128 |     4,502,128
char[]                                                           |    50,285 |    2,646,080 |     2,646,080
com.mysql.jdbc.JDBC4ResultSet                                    |     9,427 |    1,659,152 |    12,354,360
java.util.HashMap$Entry[]                                        |    19,246 |    1,641,928 |    16,387,720
java.lang.String                                                 |    51,067 |    1,634,144 |     3,951,064
com.mysql.jdbc.StatementImpl                                     |     9,427 |    1,432,904 |    15,295,672
java.util.TreeMap                                                |    28,285 |    1,357,680 |     2,495,568
com.mysql.jdbc.Field                                             |     9,417 |    1,356,048 |     2,485,064
java.util.TreeMap$Entry                                          |    28,420 |    1,136,800 |     1,137,856
java.util.HashMap                                                |    19,224 |      922,752 |    16,401,088
java.util.HashMap$Entry                                          |    22,253 |      712,096 |    16,255,280
java.lang.Object[]                                               |    10,789 |      593,000 |     1,412,184
java.lang.Object                                                 |    20,583 |      329,328 |       329,328
com.mysql.jdbc.RowDataStatic                                     |     9,417 |      301,344 |     1,054,704
java.net.SocksSocketImpl                                         |     2,572 |      288,064 |       836,096
java.util.ArrayList                                              |     9,729 |      233,496 |       830,136
com.mysql.jdbc.Field[]                                           |     9,427 |      226,168 |     2,711,224
byte[][]                                                         |     9,417 |      226,008 |       452,648
com.mysql.jdbc.ByteArrayRow                                      |     9,417 |      226,008 |       678,656
com.mysql.jdbc.ConnectionPropertiesImpl$BooleanConnectionProperty|     2,750 |      176,000 |       179,520
java.util.Hashtable$Entry                                        |     4,837 |      154,784 |       295,040
java.util.HashSet                                                |     9,460 |      151,360 |     1,372,632
Total: 22 of 2,427 entries; 2,405 more                           |   407,563 |   23,597,568 |              
------------------------------------------------------------------------------------------------------------

对于插入和更新查询,我们这样做,下面我们确保关闭语句。

 Statement stmt1 = null;
stmt1 = dbconn.createStatement();
String insertQuery3 =........
count = stmt9.executeUpdate(insertQuery3);
try{
   if ( stmt1!= null ){  stmt1.close();
}
   else{
   System.out.println("No stm1 exist");

}
}catch(SQLException ex){   System.out.println("SQLException has been caught for stmt1");
ex.printStackTrace(System.out);
}

For select we do this  

Statement stmt2 = null;
stmt2 = dbconn.createStatement(); 
String selectQuery2= .........
ResultSet rs2 = stmt2.executeQuery(selectQuery2);

if(rs2.next())
{

}
try{
   if ( rs2!= null ){  rs2.close();
   }   else{
   System.out.println("No rs2 exist");

}

   if ( stmt2!= null ){  stmt2.close();
   }   else{
   System.out.println("No stm2 exist");

}
}catch(SQLException ex){   System.out.println("SQLException has been caught for stmt2");
ex.printStackTrace(System.out);
}
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