Develop Reference

Missing slf4j in tess4j

I want to test tess4j to do OCR. I used the following tutorial for a first example: http://tess4j.sourceforge.net/codesample.html
I included the required libraries, but I am getting the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at net.sourceforge.tess4j.Tesseract.<clinit>(Unknown Source)
at tess4jexample.TesseractExample.main(TesseractExample.java:10)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 2 more
Does anyone knows a solution for this?

Tess4J has several dependencies. You'll need to include them in the classpath.

There has where still some dependencies missing, which have not been mentioned on the mavenrepository:
logback-core-1.1.6.jar
slf4j-api-1.7.21.jar
I think now it is working :-) Thank you nguyenq for this hint, to check the dependencies.

Exception in thread "main" dropbox application

I'm trying to make a simple application with Java, using Eclipse that could upload a file from my computer to Dropbox but whenever I compile, I get this error:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/http/conn/params/ConnPerRoute
at javaaplication1.JavaApplication11.main(JavaApplication11.java:32)
Caused by: java.lang.ClassNotFoundException: org.apache.http.conn.params.ConnPerRoute
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 1 more
Can you help me figure this out?
Thank you in advance.

You miss the httpclient.jar in your classpath. Download it and add it to your classpath.

eclipse errors while running custom code

While adding custom jar files in the project and executing some java code I am getting this error any idea how to solve this .There is no error in code ,it was running smoothly before this happen.
Exception in thread "main" java.lang.NoClassDefFoundError: org/aspectj/lang/Signature
at com.util.DfExSession.connectToDocbase(DfExSession.java:18)## Heading ##
at com.console.TestConsole.main(TestConsole.java:17)
Caused by: java.lang.ClassNotFoundException: org.aspectj.lang.Signature
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 2 more

Look's like the aspectjrt.jar is missing in your classptah. Download & add it to your classpath.

How to check pdf is protected using itext in java

I am using itext library to know whether the pdf file is protected or not.
i am also add boncycastle library to my class path but it still showing error:
Caused by: java.lang.ClassNotFoundException: org.bouncycastle.asn1.DEREncodable
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 7 more

Put this library in your classpath bcprov-jdk15on-1.47.jar
UPDATE
Mind your bouncy castle dependencies version according to the IText version you are using. To double check it with maven repositories. eg. here or here

How to upload files to google drive using java-Google Docs Api?

Already I used older version of the API to upload files to Google docs but now the API version is revised, so I couldn't upload.
Previously I used these lines for authorization:
DocsService service = new DocsService("MyDocumentsListIntegration-v1");
service.setUserCredentials(USERNAME, PASSWORD);
But now it is giving this error:
Exception in thread "main" java.lang.NoClassDefFoundError: javax/mail/MessagingException
at sample.main(sample.java:15)
Caused by: java.lang.ClassNotFoundException: javax.mail.MessagingException
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 1 more
Can anyone help me?

It seems like you are missing one of the external dependencies, mail.jar, which is part of Sun's JavaMail API.
Check this page for instructions on how to get it as well as all other external dependencies: https://developers.google.com/gdata/articles/java_client_lib