Bits And Pix

Docs

• Java Desktop Media
• JAI at java.net (”new” home) (old location: Java Advanced Imaging API Home Page)
• Java Doc ImageIO

Sample code links:

class EmpSortByName implements Comparator{

    public int compare(Employee o1, Employee o2) {
        return o1.getName().compareTo(o2.getName());
    }
}

....
List employees = ...;
Collections.sort(employees , new EmpSortByName());

java.lang.Comparable: int compareTo(Object o1)
This method compares this object with o1 object. Returned int value has the following meanings.

1. positive – this object is greater than o1
2. zero – this object equals to o1
3. negative – this object is less than o1

java.lang.Comparator: int compare(Object o1, Objecto2)
This method compares o1 and o2 objects. Returned int value has the following meanings.

1. positive – o1 is greater than o2
2. zero – o1 equals to o2
3. negative – o1 is less than o1

Source: Java Sorting: Comparator vs Comparable Tutorial

By default, apache commons BeanUtils does not support string value to their targeted Enum. You can write a converter for each enum, but this quickly become unmanageable.

Here is a quick fix to automatically convert the string value to the targeted enum.

BeanUtilsBean beanUtilsBean = new BeanUtilsBean(new ConvertUtilsBean(){
            @Override
            public Object convert(String value, Class clazz) {
                  if (clazz.isEnum()){
                       return Enum.valueOf(clazz, value);
                  }else{
                       return super.convert(value, clazz);
                  }
           }
        });

Now, you can call beanUtilsBean.populate(bean,map) even for enum values.

Here is the minimum code to support DataSourceTransactionManager thread bound session  (similar to OpenSessionInViewInterceptor).

For each thread:

public void beginThreadSession(SessionFactory sessionFactory){

  Session session = SessionFactoryUtils.getSession(sessionFactory, true);
  TransactionSynchronizationManager.bindResource(sessionFactory,
                                               new SessionHolder(session));

}

public void endThreadSession(SessionFactory sessionFactory){

  SessionHolder sessionHolder =
    (SessionHolder) TransactionSynchronizationManager.unbindResource(sessionFactory);
  SessionFactoryUtils.closeSession(sessionHolder.getSession());

}

DataSourceTransactionManager will pickup the thread bound session with SessionFactoryUtils. The trick is calling the “un/bindResource” methods. This set one session for all your requests and transactions for a given thread (and use the @transactional if you have configured it as follow).

<aop:config proxy-target-class="true"/>

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
    <property name="configurationClass" value="org.hibernate.cfg.AnnotationConfiguration"/>
    <property name="configLocation" value="config/hibernate.cfg.xml"/>
    <property name="dataSource" ref="dataSource"/>
</bean>

<tx:annotation-driven transaction-manager="txManager"/>

<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource"/>
</bean>

Obviously, this is the strict minimum code (good of unit testing for example). For Web App, use the OpenSessionInViewInterceptor.

<bean id="openSessionInView"
class="org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor">
    <property name="sessionFactory" ref="sessionFactory"/>
    <!-- optional
    <property name="flushModeName" value="FLUSH_NEVER" />
    -->
</bean>

Hibernate inheritance and relationship could lead to the following exception:

Caused by: org.hibernate.WrongClassException: Object with id: 3 was not of the
specified subclass...
...
        at org.hibernate.loader.Loader.instanceAlreadyLoaded(Loader.java:1267)
        at org.hibernate.loader.Loader.getRow(Loader.java:1219)
        at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:603)
        at org.hibernate.loader.Loader.doQuery(Loader.java:724)
...

Putting @ForceDiscriminator near the @DiscriminatorValue(..) of your respective classes might solve the problem.
See Hibernate Annotation Doc

This usually happen when the client connection pool maintained connection longer than the database connection. Fix: set the maxIdleTime property:

 <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
  <property name="driverClass" value="${db.driverClass}" />
  <property name="jdbcUrl" value="${db.jdbcUrl}" />
  <property name="user" value="${db.user}" />
  <property name="password" value="${db.password}" />
  <!-- 1/2 hr. MySQL server default connection timeout is 43200 (12hrs) -->
  <property name="maxIdleTime" value="1800" />
 </bean>

Information Source: Broken pipe

Requirements:

• OpenOffice installed and OpenOffice started (e.g., OpenOffice in the system tray on Windows)
• Java

Quick steps to test:

1. Download the latest JODConverter 3.x from google code.
2. Unzip the jar file
3. Do a quick test:
   java -jar lib/jodconverter-${version}.jar test.odt test.pdf
4. you should see something like

   C:\apps\jodconverter-3.0-beta-1>java -jar lib/jodconverter-3.0-beta-1.jar test.odt test.pdf
   
   Apr 9, 2009 12:56:42 PM net.sf.jodconverter.office.OfficeProcess start
   INFO: starting process with acceptString 'socket,host=127.0.0.1,port=8100' and
   profileDir 'C:\Users\JEREMY~1\AppData\Local\Temp\.jodconverter_socket_host-127.0.0.1_port-8100'
   Apr 9, 2009 12:56:42 PM net.sf.jodconverter.office.OfficeProcess start
   INFO: started process; pid -1
   Apr 9, 2009 12:56:47 PM net.sf.jodconverter.office.OfficeConnection connect
   INFO: connected: 'socket,host=127.0.0.1,port=8100'
   Apr 9, 2009 12:56:52 PM net.sf.jodconverter.office.OfficeConnection$1 disposing
   INFO: disconnected: 'socket,host=127.0.0.1,port=8100'
   Apr 9, 2009 12:56:53 PM net.sf.jodconverter.office.ManagedOfficeProcess doEnsureProcessExited
   INFO: process exited with code 0

Note: As you can see it works because it assumes that OpenOffice listen to the port 8100, which happen to be the case (how lucky!).

In a Java (Server) App:

1. Copy the following .jar files in your webapp lib directory
   lib/jodconverter-3.0-beta-1.jar
   lib/juh-3.0.0.jar
   lib/jurt-3.0.0.jar
   lib/ridl-3.0.0.jar
   lib/unoil-3.0.0.jar
2. Use the following code snippet:

   OfficeManager officeManager = new ManagedProcessOfficeManager();
   officeManager.start();
   
   OfficeDocumentConverter converter = new OfficeDocumentConverter(officeManager);
   converter.convert(sourceFile,targetFile);
   
   officeManager.stop();

• Java Tutorials RegEx
• Using Regular Expressions in Java

Reading/Writing Word and PDF document could be quite tricky.

For Word (.doc), the best option seems to be using OpenOffice to convert the file to a text format (RTF or OpenOffice XML format), modify the text document, and use OpenOffice to convert back to .doc. JODConverter 3.x seems to be a great option for doing that in a Web Application.

For PDF, iText seems to be the solution.

There seems to be also a very complete and mature commercial product for Java which is Aspose. It supports direct access to Office documents such as .doc file allowing to preserve any meta data such as revision and such. Its a little pricey but manageable for a SaaS application, although, I am not sure how their definition of “location” applies to a SaaS application.

Here are some pointers:

Word:

• First an EXCELLENT document about Microsoft binary file format: Why are the Microsoft Office file formats so complicated? (And some workarounds)
• JODConverter 3.x (still beta): Java API using OpenOffice converter. Pros: Very complete; Cons: Require Native. JODConverter 2.x (not maintained anymore)
• OpenOffice.org UNO: API to OpenOffice (Java, C++, …) (Example 1)
• HWPF (from POI): Java API to read/write OLE document. Pros: Pure java; Cons: Not maintained and incomplete (the HWPF part)
• Eclipse BIRT: (see Adam’s comment)
• Microsoft Office (97-2003) Binary format. (Do not waste your time with this, Why are the Microsoft Office file formats so complicated? (And some workarounds )

RTF:

• Generate RTF Word Documents Using a Java Application (using iText): iText can only write RTF (not read)
• RTF2FO (commercial $150/CPU, $750/site): RTF to XML converter.
• RTF-TO-XML (similar price than RTF2FO)
• Majix: Not maintained anymore (last release was in 2004)

PDF:

• IText (download): Java Lib to read/create PDF document.
• FOP: reads a formatting object (FO) tree and renders the resulting pages to a specified output (The primary output target is PDF)

When setting the expires date in Servlet, better to set the cache-control as well.

final int CACHE_DURATION_IN_SECOND = 60 * 60 * 24 * 2; // 2 days
final long   CACHE_DURATION_IN_MS = CACHE_DURATION_IN_SECOND  * 1000;
long now = System.currentTimeMillis();
//res being the HttpServletResponse of the request
res.addHeader("Cache-Control", "max-age=" + CACHE_DURATION_IN_SECOND);
res.addHeader("Cache-Control", "must-revalidate");//optional
res.setDateHeader("Last-Modified", now);
res.setDateHeader("Expires", now + CACHE_DURATION_IN_MS);

For no cache

res.setHeader("Pragma", "No-cache");
res.setHeader("Cache-Control", "no-cache,no-store,max-age=0");
res.setDateHeader("Expires", 1);