Category Archives: Struts

Using Log4j to log Hibernate queries with values

Hi All,

Hibernate is one of most used ORM framework across the J2EE Applications, It provides many features which helps us to organize the SQL queries in a very easy manner just by playing with java entity bean properties. In this post I will explain the way we can display the named queries in log file including the run time value bindings,

In bigger applications debugging SQL queries is a very crucial thing came into picture, a query containing more SQL Joins is not that easy to debug in case if some misalignment in data found.  To ease that just follow the below steps to enable this sort of hibernate logging in logger(LOG4J).


In Log4j properties add the below two category entries.

log4j.category.org.hibernate.SQL= STDOUT // this is as equivalent hibernate.show_sql=true
log4j.category.org.hibernate.type= DEBUG// this basically prints the bound parameters among other things.

Output in Logger file

Hibernate: select emp0_.dept_id as dept2_1_, emp0_.emp_id as emp1_1_, emp0_.emp_id as emp1_0_0_, emp0_.dept_id as dept2_0_0_, emp0_.emp_join_date as emp3_0_0_, emp0_.emp_name as emp4_0_0_, emp0_.bank_name as bank5_0_0_, emp0_.salary as salary0_0_ from Employee emp0_ where emp0_.dept_id=?
2011-12-03 13:08:50,031 DEBUG [main] AbstractBatcher – preparing statement
2011-12-03 13:08:50,031 DEBUG [main] NullableType – binding ‘1’ to parameter: 1
2011-12-03 13:08:50,031 DEBUG [main] AbstractBatcher – about to open ResultSet (open ResultSets: 0, globally: 0)

Hope this helps 🙂


Thanks
R Vashi

JPA/Hibernate:- java.lang.IllegalStateException: No data type for node

Hi,

Few days back I got struck with one of the hiberante exception I was facing while running one named query.

Exception Details:

Exception in thread "main" java.lang.IllegalStateException: No data type for node: org.hibernate.hql.ast.tree.IdentNode
 \-[IDENT] IdentNode: 'dpt' {originalText=dpt}

As I haven’t work as that extensive on JPA, due to that I was not able to catch early the root cause of this exception 😦 , After carefully examining around all the entity classes, Then I came to know about the orgin of this issue.

Named Query which was used to fetch the department details.(The below query scenario represent imaginary situation)

select dpt.id.deptId from Dept dept

The root cause was the alias name being used for the Entity reference. Alias name ‘dept‘ should have been used in the SELECT Clause of the HQL. Where as it was referring to ‘dpt‘ and was causing this exception.

Right named query:

select dept.id.deptId from Dept dept

Hope this helps.


Thanks,
R Vashi

Useful JVM tunings

Categories of Java HotSpot VM Options

Standard options recognized by the Java HotSpot VM are described on the Java Application Launcher reference pages for Windows, Solaris and Linux. This document deals exclusively with non-standard options recognized by the Java HotSpot VM:

* Options that begin with -X are non-standard (not guaranteed to be supported on all VM implementations), and are subject to change without notice in subsequent releases of the JDK.
* Options that are specified with -XX are not stable and are not recommended for casual use. These options are subject to change without notice.

Some Useful -XX Options

Default values are listed for Java SE 6 for Solaris Sparc with -server. Some options may vary per architecture/OS/JVM version. Platforms with a differing default value are listed in the description.

* Boolean options are turned on with -XX:+<option> and turned off with -XX:-<option>.
* Numeric options are set with -XX:<option>=<number>. Numbers can include ‘m’ or ‘M’ for megabytes, ‘k’ or ‘K’ for kilobytes, and ‘g’ or ‘G’ for gigabytes (for example, 32k is the same as 32768).
* String options are set with -XX:<option>=<string>, are usually used to specify a file, a path, or a list of commands

Flags marked as manageable are dynamically writeable through the JDK management interface (com.sun.management.HotSpotDiagnosticMXBean API) and also through JConsole. In Monitoring and Managing Java SE 6 Platform Applications, The manageable flags can also be set through jinfo -flag.

The options below are loosely grouped into three categories.

* Behavioral options change the basic behavior of the VM.
* Performance tuning options are knobs which can be used to tune VM performance.
* Debugging options generally enable tracing, printing, or output of VM information.

1. Behavioral Options

Option and Default Value

Description
-XX:-AllowUserSignalHandlers    Do not complain if the application installs signal handlers. (Relevant to Solaris and Linux only.)

-XX:AltStackSize=16384    Alternate signal stack size (in Kbytes). (Relevant to Solaris only, removed from 5.0.)

-XX:-DisableExplicitGC    Disable calls to System.gc(), JVM still performs garbage collection when necessary.

-XX:+FailOverToOldVerifier    Fail over to old verifier when the new type checker fails. (Introduced in 6.)

-XX:+HandlePromotionFailure    The youngest generation collection does not require a guarantee of full promotion of all live objects. (Introduced in 1.4.2 update 11) [5.0 and earlier: false.]

-XX:+MaxFDLimit    Bump the number of file descriptors to max. (Relevant  to Solaris only.)

-XX:PreBlockSpin=10    Spin count variable for use with -XX:+UseSpinning. Controls the maximum spin iterations allowed before entering operating system thread synchronization code. (Introduced in 1.4.2.)

-XX:-RelaxAccessControlCheck    Relax the access control checks in the verifier. (Introduced in 6.)

-XX:+ScavengeBeforeFullGC    Do young generation GC prior to a full GC. (Introduced in 1.4.1.)

-XX:+UseAltSigs    Use alternate signals instead of SIGUSR1 and SIGUSR2 for VM internal signals. (Introduced in 1.3.1 update 9, 1.4.1. Relevant to Solaris only.)

-XX:+UseBoundThreads    Bind user level threads to kernel threads. (Relevant to Solaris only.)

-XX:-UseConcMarkSweepGC    Use concurrent mark-sweep collection for the old generation. (Introduced in 1.4.1)

-XX:+UseGCOverheadLimit    Use a policy that limits the proportion of the VM’s time that is spent in GC before an OutOfMemory error is thrown. (Introduced in 6.)

-XX:+UseLWPSynchronization    Use LWP-based instead of thread based synchronization. (Introduced in 1.4.0. Relevant to Solaris only.)

-XX:-UseParallelGC    Use parallel garbage collection for scavenges. (Introduced in 1.4.1)

-XX:-UseParallelOldGC    Use parallel garbage collection for the full collections. Enabling this option automatically sets -XX:+UseParallelGC. (Introduced in 5.0 update 6.)

-XX:-UseSerialGC    Use serial garbage collection. (Introduced in 5.0.)

-XX:-UseSpinning    Enable naive spinning on Java monitor before entering operating system thread synchronizaton code. (Relevant to 1.4.2 and 5.0 only.) [1.4.2, multi-processor Windows platforms: true]

-XX:+UseTLAB    Use thread-local object allocation (Introduced in 1.4.0, known as UseTLE prior to that.) [1.4.2 and earlier, x86 or with -client: false]

-XX:+UseSplitVerifier    Use the new type checker with StackMapTable attributes. (Introduced in 5.0.)[5.0: false]

-XX:+UseThreadPriorities    Use native thread priorities.

-XX:+UseVMInterruptibleIO    Thread interrupt before or with EINTR for I/O operations results in OS_INTRPT. (Introduced in 6. Relevant to Solaris only.)

2. Performance Options

Option and Default Value
Description
-XX:+AggressiveOpts    Turn on point performance compiler optimizations that are expected to be default in upcoming releases. (Introduced in 5.0 update 6.)

-XX:CompileThreshold=10000    Number of method invocations/branches before compiling [-client: 1,500]

-XX:LargePageSizeInBytes=4m    Sets the large page size used for the Java heap. (Introduced in 1.4.0 update 1.) [amd64: 2m.]

-XX:MaxHeapFreeRatio=70    Maximum percentage of heap free after GC to avoid shrinking.

-XX:MaxNewSize=size    Maximum size of new generation (in bytes). Since 1.4, MaxNewSize is computed as a function of NewRatio. [1.3.1 Sparc: 32m; 1.3.1 x86: 2.5m.]

-XX:MaxPermSize=64m    Size of the Permanent Generation.  [5.0 and newer: 64 bit VMs are scaled 30% larger; 1.4 amd64: 96m; 1.3.1 -client: 32m.]

-XX:MinHeapFreeRatio=40    Minimum percentage of heap free after GC to avoid expansion.

-XX:NewRatio=2    Ratio of new/old generation sizes. [Sparc -client: 8; x86 -server: 8; x86 -client: 12.]-client: 4 (1.3) 8 (1.3.1+), x86: 12]

-XX:NewSize=2.125m    Default size of new generation (in bytes) [5.0 and newer: 64 bit VMs are scaled 30% larger; x86: 1m; x86, 5.0 and older: 640k]

-XX:ReservedCodeCacheSize=32m    Reserved code cache size (in bytes) – maximum code cache size. [Solaris 64-bit, amd64, and -server x86: 48m; in 1.5.0_06 and earlier, Solaris 64-bit and and64: 1024m.]

-XX:SurvivorRatio=8    Ratio of eden/survivor space size [Solaris amd64: 6; Sparc in 1.3.1: 25; other Solaris platforms in 5.0 and earlier: 32]

-XX:TargetSurvivorRatio=50    Desired percentage of survivor space used after scavenge.

-XX:ThreadStackSize=512    Thread Stack Size (in Kbytes). (0 means use default stack size) [Sparc: 512; Solaris x86: 320 (was 256 prior in 5.0 and earlier); Sparc 64 bit: 1024; Linux amd64: 1024 (was 0 in 5.0 and earlier); all others 0.]

-XX:+UseBiasedLocking    Enable biased locking. For more details, see this tuning example. (Introduced in 5.0 update 6.) [5.0: false]

-XX:+UseFastAccessorMethods    Use optimized versions of Get<Primitive>Field.

-XX:-UseISM    Use Intimate Shared Memory. [Not accepted for non-Solaris platforms.] For details, see Intimate Shared Memory.

-XX:+UseLargePages    Use large page memory. (Introduced in 5.0 update 5.) For details, see Java Support for Large Memory Pages.

-XX:+UseMPSS    Use Multiple Page Size Support w/4mb pages for the heap. Do not use with ISM as this replaces the need for ISM. (Introduced in 1.4.0 update 1, Relevant to Solaris 9 and newer.) [1.4.1 and earlier: false]

-XX:+StringCache    Enables caching of commonly allocated strings.

-XX:AllocatePrefetchLines=1    Number of cache lines to load after the last object allocation using prefetch instructions generated in JIT compiled code. Default values are 1 if the last allocated object was an instance and 3 if it was an array.

-XX:AllocatePrefetchStyle=1    Generated code style for prefetch instructions.
0 – no prefetch instructions are generate*d*,
1 – execute prefetch instructions after each allocation,
2 – use TLAB allocation watermark pointer to gate when prefetch instructions are executed.

3. Debugging Options

Option and Default Value
Description
-XX:-CITime    Prints time spent in JIT Compiler. (Introduced in 1.4.0.)

-XX:ErrorFile=./hs_err_pid<pid>.log    If an error occurs, save the error data to this file. (Introduced in 6.)

-XX:-ExtendedDTraceProbes    Enable performance-impacting dtrace probes. (Introduced in 6. Relevant to Solaris only.)

-XX:HeapDumpPath=./java_pid<pid>.hprof    Path to directory or filename for heap dump. Manageable. (Introduced in 1.4.2 update 12, 5.0 update 7.)

-XX:-HeapDumpOnOutOfMemoryError    Dump heap to file when java.lang.OutOfMemoryError is thrown. Manageable. (Introduced in 1.4.2 update 12, 5.0 update 7.)

-XX:OnError=”<cmd args>;<cmd args>”    Run user-defined commands on fatal error. (Introduced in 1.4.2 update 9.)

-XX:OnOutOfMemoryError=”<cmd args>;
<cmd args>”     Run user-defined commands when an OutOfMemoryError is first thrown. (Introduced in 1.4.2 update 12, 6)

-XX:-PrintClassHistogram    Print a histogram of class instances on Ctrl-Break. Manageable. (Introduced in 1.4.2.) The jmap -histo command provides equivalent functionality.

-XX:-PrintConcurrentLocks    Print java.util.concurrent locks in Ctrl-Break thread dump. Manageable. (Introduced in 6.) The jstack -l command provides equivalent functionality.

-XX:-PrintCommandLineFlags    Print flags that appeared on the command line. (Introduced in 5.0.)

-XX:-PrintCompilation    Print message when a method is compiled.

-XX:-PrintGC    Print messages at garbage collection. Manageable.

-XX:-PrintGCDetails    Print more details at garbage collection. Manageable. (Introduced in 1.4.0.)

-XX:-PrintGCTimeStamps    Print timestamps at garbage collection. Manageable (Introduced in 1.4.0.)

-XX:-PrintTenuringDistribution    Print tenuring age information.

-XX:-TraceClassLoading    Trace loading of classes.

-XX:-TraceClassLoadingPreorder    Trace all classes loaded in order referenced (not loaded). (Introduced in 1.4.2.)

-XX:-TraceClassResolution    Trace constant pool resolutions. (Introduced in 1.4.2.)

-XX:-TraceClassUnloading    Trace unloading of classes.

-XX:-TraceLoaderConstraints    Trace recording of loader constraints. (Introduced in 6.)

-XX:+PerfSaveDataToFile    Saves jvmstat binary data on exit.

source http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html


Thanks
R Vashi

Download a file using Response headers

Hi All,

We sometime struggle implementing a functionality to download a file through browser download dialog window.

The below example will demonstrate the way we can download a file using response headers.

There are few steps you need to follow:

Step 1: First of all set the Content Type, for example if you want to set the file extension to Excel then.

response.setContentType(“application/vnd.ms-excel”);

Step 2: Now in this step we will set the response headers so that the browser can display the save and open prompt for the file.
Content-disposition is an extension to the MIME protocol that instructs a MIME user agent on how it should display an attached file.When Internet Explorer/Mozilla/any browser receives the header, it raises a File Download dialog box whose file name box is automatically populated with the file name that is specified in the header.

response.setHeader(“Content-Disposition”, “attachment;filename=” + MYFILE+”_TEST”+version_no+”.xls”)

Step 3: In this step we will add the data to the file which we are going to download.

response.getOutputStream().print(myData); // here my data is CSV formatted data

Step 4: Now access the servlet/jsp, the moment it loads you will see download window asking for save/open a file.

e.g http://localhost:8080/myapp/downlodReport

Hope this helps.


Thanks
R Vashis

Creating JNDI Data Source in Tomcat to Connect Oracle Data Source

Hi All,

In this article I will show how to create a JNDI data source in Tomcat.

When building a J2EE based application,  the daunting task we see first is the DB connectivity management. And then the Connection Pool implementation comes into the practise.  But there is always lots of issues observed by configuring data sources in web application servers.

The normal practise which every development team does is to provide the data source configuration(user/password, DB URL etc), add the JDBC drivers, define various settings for pool management.

Tomcat allows us to define this configuration context wise or application reference wise.

To define the Web Server Context wise. Simply go to [TOMCAT_HOME]/conf/server.xml, and add the the below configuration.

<Context docBase=”myapp” path=”/myapp” reloadable=”true” source=”org.eclipse.jst.j2ee.server:myapp”>
<Resource auth=”Container” connectionCacheName=”TestCache” connectionCacheProperties=”{MaxStatementsLimit=0, MinLimit=0, InitialLimit=0, ValidateConnection=true, ConnectionWaitTimeout=600, MaxLimit=10000}” connectionCachingEnabled=”true” driverclassname=”oracle.jdbc.driver.OracleDriver” factory=”oracle.jdbc.pool.OracleDataSourceFactory” name=”DataSourceName” scope=”Shareable” type=”oracle.jdbc.pool.OracleDataSource” url=”jdbc:oracle:thin:@HOST_IP:PORT:SID” password=”pa$$w0rd” user=”pooluser”/>
</Context>

To Define the configuration for application scope,
Simply create Context.xml and add the below configuration.

<Context>
<Resource name=”jdbc/DataSourceName” auth=”Container”
type=”oracle.jdbc.pool.OracleDataSource”
driverClassName=”oracle.jdbc.driver.OracleDriver”
url=”jdbc:oracle:thin:@HOST_IP:PORT:SID” password=”pa$$w0rd” user=”pooluser”
maxActive=”8″
/>
</Context>

path – this defines the name of the application
connectionCacheProperties- defines the variuos connection pool settings
driverclassname – defines the driver manager class name
name – DataSourceName [JNDI Name]
URL – DB host URL
user – connection pool user
password – password
type – defines the type of data source

Once the configuration is added,  add the Context.xml into META-INF folder of Applications .WAR file.
Now in Your JSP/Servlet/Data Access Layer add the below code to get the Connection from Data Source via JNDI lookup.

DataSource ds = (DataSource) ic.lookup(“java:comp/env/jdbc/DataSourceName”);
Connection c = ds.getConnection();

[NOTE] This only works with Tomcat, as every Web Application server have their own implementation for the same.


Thanks
R Vashi

ServletContext getRealPath cause problems on Weblogic

Hi All,

Sometime we face issues with the application where some of the Jsp/servlets try to access the resources using getRealPath of the ServletContext class.

The problem is that it works only when you explode the war file. Even there is a CR CR299135 for the weblogic 10+ versions to tackle this issue.

You have to configure the <show-archived-real-path-enabled> flag to let weblogic returns the actual path of the application.

This configuration can be applied 2 ways.

1. Domain Level

2  Application Level

1. For setting Domain Level: Open the config.xml and set the

<web-app-container>

<show-archived-real-path-enabled>true</show-archived-real-path-enabled>

</web-app-container>

2 Now to configure at Application Level, in weblogic.xml

<container-descriptor>

<show-archived-real-path-enabled>true</show-archived-real-path-enabled>

</container-descriptor>

Hope this helps.


Thanks
R Vashi

How to read SQL Collection type in java JDBC

Hi All,

In this article I will show how to use SQL Collection in java code to read values. As collections are very easy way to pass data to java layer. It helps in eliminating the use of cursors in the procedure.

SQL Type
declare SQL Collection type
Set length of 3

java code


cst = getConnection().prepareCall(“{MY_PROC(?,?,?,?)}”);
cst.setString(1,usrId);
cst.registerOutParameter(2,OracleTypes.ARRAY, “SCHEMA.TABLE_TYPE_NAME”); // Register the output parameter type
cst.registerOutParameter(3,Types.INTEGER);
cst.registerOutParameter(4,Types.VARCHAR);

//execute the Query
cst.executeQuery();

Array arryType = cst.getArray(4);  // use Get ARRAY To fetch the SQL Collection into array object
ResultSet rs = arryType.getResultSet(); // covert the arryType to ResultSet object

if(rs!=null){

while(rs.next()){
Struct strct = (Struct) rs.getObject(2);  // Cast the object in Struct Type
Object[] attributes = strct.getAttributes();
//now start reading one by one
// in my collection my array size is 3

System.out.println(String.valueOf(attributes[0]));
System.out.println(String.valueOf(attributes[1]));
System.out.println(String.valueOf(attributes[2]));
}

}

Hope this helps

Thanks
R Vashi