Spring boot ActiveMQ example

ActiveMQ Setup

Download the latest version of ActiveMQ from below link

https://activemq.apache.org/components/classic/download/

Extract the zip file, go to bin folder and start activemq server using activemq.bat

In my case it is
apache-activemq-5.15.11/bin/win32/activemq.bat

Verify ActiveMQ server is UP and running

http://localhost:8161/

Note - You can change the default port 8161 by updating below file
apache-activemq-5.15.11/conf/jetty.xml

Go to admin page

http://localhost:8161/admin/

Login with default credentials

Username - admin
Password - admin

Note - You can change default credentials by updating below file
apache-activemq-5.15.11/conf/jetty-realm.properties

Here is how our data will flow

Read/Write large excel (xlsx) file

In this article you will see how to write a huge excel file.

Using SXSSFWorkbook you can write large excel file. It is a Streaming version of XSSFWorkbook implementing the "BigGridDemo" strategy. This allows to write very large files without running out of memory as only a configurable portion of the rows are kept in memory at any one time.

Note - I have tested it to write 10,48,576 rows which created 40 MB excel file. If you want to write more rows than this then you may opt to write CSV file.

You need to add below dependencies in your pom.xml

How to install maven and create a new blank maven project

Step 1 - Go to maven site and download maven binary zip archive as shown below

https://maven.apache.org/download.cgi

Step 2 - Once you download the file extract it to a particular location and set below Windows environment variables

 

M2_HOME - C:\TestMaven\apache-maven-3.5.0
MAVEN_HOME - C:\TestMaven\apache-maven-3.5.0

PATH - C:\TestMaven\apache-maven-3.5.0\bin

Make sure that JDK is installed and "JAVA_HOME" variable is added in your Windows environment variable

Now test maven using below command

mvn -version

 

Note - You can change the default maven localRepository as per your requirement, just go to apache-maven-3.5.0/conf/settings.xml and change the path

<localRepository>C:/TestMaven/repo</localRepository>

Java - JAXB marshalling and unmarshalling of ArrayList

Marshalling and unmarshalling of ArrayList using JAXB is rather simple however you cannot directly marshall ArrayList. You will need a holder class (wrapper class). It will hold the arraylist that you want to marshall or unmarshall.

Please see the self explanatory java code below -

Output -

--Marshalling--
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<List>
    <Value>one</Value>
    <Value>two</Value>
    <Value>three</Value>
</List>

--Unmarshalling--

[one, two, three]

Java program to create doc/docx file

Apache POI can be used to create a doc/docx file. To know more click here.

You can download latest version of jar files(i.e. poi-bin-3.10-FINAL-20140208.zip) form below link.
http://poi.apache.org/download.html

Add below mentioned Jar files in your classpath -

• poi-3.10-FINAL-20140208.jar
• poi-ooxml-3.10-FINAL-20140208.jar
• poi-ooxml-schemas-3.10-FINAL-20140208.jar
• poi-scratchpad-3.10-FINAL-20140208.jar
• xmlbeans-2.3.0.jar
• dom4j-1.6.1.jar

Please see the self explanatory java code below

Java program to read doc/docx file

Apache POI can be used to read doc/docx file. To know more click here.

You can download latest version of jar files(i.e. poi-bin-3.10-FINAL-20140208.zip) form below link.
http://poi.apache.org/download.html

Add below mentioned Jar files in your classpath -

• poi-3.10-FINAL-20140208.jar
• poi-ooxml-3.10-FINAL-20140208.jar
• poi-ooxml-schemas-3.10-FINAL-20140208.jar
• poi-scratchpad-3.10-FINAL-20140208.jar
• xmlbeans-2.3.0.jar
• dom4j-1.6.1.jar

Please see the self explanatory java code below

Java : Encode/Decode Base64

We will be using Apache Commons codec to Encode and Decode Base64 data.

Apache Commons Codec (TM) software provides implementations of common encoders and decoders such as Base64, Hex, Phonetic and URLs. To know more, click here.

To run below example you will need to add commons-codec.jar in your classpath. Download commons-codec-1.4.jar.

Please see the self explantory java code below.

Implementation of Restful Webservice with image

In Java EE 6, JAX-RS provides the functionality for Representational State Transfer (RESTful) web services. REST is well suited for basic, ad hoc integration scenarios. RESTful web services, often better integrated with HTTP than SOAP-based services are, do not require XML messages or WSDL service–API definitions. Before proceeding please read this article, Developing RESTful Web Services with JAX-RS.

Also please have look at the tutorial about "JAXB marshalling and unmarshalling", as it would be helpful to understand Restful Webservice.

For running this example, below mentioned particulars are used.

• Tomcat 7.0.11
• JDK 1.5
• MyEclipse 8.6.1

1. Create a new Web Service Project, File -> New -> Web Service Project

Java program to download file from url

Below is the java program to download a file from url.

Java - Read excel file with blank cells

If you use normal cellIterator to iterate through excel cells it will skip blank cells. If you need to read blank cells as well you can use below method -

Lucene - Updating index for an existing file

Updating index files could mean below two possibilities -

• Adding a new file to existing index
• Updating an existing file

Adding a new file to an existing index

Adding a new file is very simple. Please see my previous article. click here.

Updating an existing file

When you do IndexWriter.add() for a document that is already in the index it won't overwrite the previous document instead it will add multiple copies of the same document in the index.

There is no direct update procedure in Lucene. To update an index incrementally you must first delete the documents that were updated, and then re-add them to the index. In this example we will see how to delete a file and then you can re-add the same file with the help of my previous article. click here.

How to delete a documents from the index?

IndexWriter allows you to delete by Term or by Query. The deletes are buffered and then periodically flushed to the index, and made visible once commit() or close() is called.

IndexReader can also delete documents, by Term or document number, but you must close any open IndexWriter before using IndexReader to make changes (and, vice/versa). IndexReader also buffers the deletions and does not write changes to the index until close() is called, but if you use that same IndexReader for searching, the buffered deletions will immediately take effect. Unlike IndexWriter's delete methods, IndexReader's methods return the number of documents that were deleted.

Generally it's best to use IndexWriter for deletions, unless 1) you must delete by document number, 2) you need your searches to immediately reflect the deletions or 3) you must know how many documents were deleted for a given deleteDocuments invocation.

If you must delete by document number but would otherwise like to use IndexWriter, one common approach is to make a primary key field, that holds a unique ID string for each document. Then you can delete a single document by creating the Term containing the ID, and passing that to IndexWriter's deleteDocuments(Term) method.

Once a document is deleted it will not appear in TermDocs nor TermPositions enumerations, nor any search results. Attempts to load the document will result in an exception. The presence of this document may still be reflected in the docFreq statistics, and thus alter search scores, though this will be corrected eventually as segments containing deletions are merged.

To know more, click here.

Java : Read / Write Excel file (.xls or .xlsx) using Apache POI

We will see how we can read or write excel file (.xls or .xlsx) using Apache POI. To know more about Apache POI, click here.

You can download latest version of JAR files from http://poi.apache.org/download.html.

In our case we are using Apache POI 3.8. To run below example you will need to download poi-bin-3.8-20120326.zip file from http://poi.apache.org/download.html. You will get below JAR files, add those in your claspath.

• dom4j-1.6.1.jar
• xmlbeans-2.3.0.jar
• poi-3.8-20120326.jar
• poi-ooxml-3.8-20120326.jar
• poi-ooxml-schemas-3.8-20120326.jar

Please see the self explanatory Java code.

Lucene - Updating index files

Apache Lucene(TM) is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.
Apache Lucene is an open source project available for free download. To know more about Lucene , click here.

In this example we will see how to append to an existing lucene index. We will see how we can update the existing index files with new data.

IndexWriter iwriter = new IndexWriter(directory, analyzer, false, MaxFieldLength.UNLIMITED);

Note the boolean variable - true to create the index or overwrite the existing one; false to append to the existing index. To know more about IndexWriter, see API.

About the example: We will create few text files. Then use our java program to create index and search. Then we will add a new file, update the index and search again.

First we will create few text files in a location lets say "C:\TestLucene\files"

How to use Apache Axis2 for consuming a web service?

About the example:


In this example we will see how to use rather consume a web service using Apache Axis2. We have a Hello World web service which is already published, it accepts a String name and prints Hello name in return. To know more about how to publish a web service, click here.

Below are the steps which shows how to consume a web service using Apache Axis2

1. Download latest version of axis2 files from http://axis.apache.org/axis2/java/core/. (i.e. axis2-1.6.2-bin.zip).


2. Extract the folder (i.e. axis2-1.6.2) in your desire location. Lets assume as C:\axis2-1.6.2.

3. Add enviroment variable AXIS2_HOME and set the value "C:\axis2-1.6.2". Also make sure that JAVA_HOME is set in enviroment variables.

4. Now you can use wsdl2java.bat file from folder "C:\axis2-1.6.2\bin" to download web service stubs. Use command prompt and go to folder C:\axis2-1.6.2\bin and run below command.

   wsdl2java.bat -uri http://localhost:8080/SimpleWebservice/hellows?wsdl

   Note : Provide your wsdl URL in above command, you can also use XSD file instead of wsdl URL. Here we have already published a hello world web services. To know how to publish a simple hello world web service, click here.

   Please see the screen shot below.

Lucene 3.0 example - Indexing and searching database tables

Apache Lucene(TM) is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.
Apache Lucene is an open source project available for free download. To know more about Lucene , click here.

About the example:

Here is the simple java program which will create index files from the data which is fetched from database. And it will perform search from the created index files and display the results. We are using Lucene 3.0 and My SQL. The basics behind is very simple, we will fetch data from database using JDBC (you can use Hibernate or so accordingly) and create index files.

You can store database column(s) in the index files depending upon your requirement. If you want to perform search in one or two column only then no need to add all columns in index files. You can store that particular column and primary key, and perform search on that column and retrieve primary key and use it accordingly.

Creating index is simple and straight forward just add the filed and filed values in Document. Searching can be done in many ways as per requirement, if you want to perform search on one filed then you can use QueryParser, for searching multiple field you can use MultiFieldQueryParser. In query you can use wild card (e.g. DATA*), logical operators (e.g DATA1 OR DATA2) etc.

To run below example please add lucene-core-3.0.2.jar (For Lucene) and mysql-connector-java-5.1.5.jar (For JDBC - My SQL) in your application's classpath.
To download lucene-core-3.0.2.jar, click here.
How to install My SQL, click here.

Java : Create xls or xlsx files using Apache's POI

Apache's POI-HSSF and POI-XSSF is a Java API to access Microsoft Excel Format Files.

HSSF is used to create Excel '97(-2007) file format and XSSF is used to create Excel 2007 OOXML (.xlsx) file format.

HSSF and XSSF provides ways to read spreadsheets create, modify, read and write XLS spreadsheets. They provide:

• low level structures for those with special needs
• an eventmodel api for efficient read-only access
• a full usermodel api for creating, reading and modifying XLS files

To know more, click here

To run below programs you will need to add POI jar file i.e. poi-bin-3.8-20120326.zip. To download latest version of jar files, click here

For running below programs i have used apache poi-3.8. First we will create .xls file then we will see how to create .xlsx file

JSP : Simple File Uploading Codes.

We will see how to upload a file using JSP, you can upload a file to your desire location with desire name. Please see the simple self explanatory codes below.

Please add below mentioned jar files in your applications classpath.

• commons-fileupload-1.2.jar (http://commons.apache.org/fileupload)
• commons-io-1.4.jar (http://commons.apache.org/io)

1st HTML interface (can be used in JSP as well)

FileUploadingInterface.HTML


<HTML>
<HEAD>
<TITLE>File Uploading Interface</TITLE>
</HEAD>
<BODY>
<center>
<h3>Simple File Uploading Example</h3>
<form action="ProcessUploadedFile.jsp" method="post" enctype="multipart/form-data">
Name <input type="text" name="userName"> (optional) </br></br>
File <input type="file" name="file1"> </br></br> <!-- Here You Can Add more numbers of Files For Uploading -->
<input type="submit" value="Submit">
</form>
</center>
</BODY>
</HTML>



2nd JSP code


ProcessUploadedFile.jsp


<%@ page import="java.io.*" %>
<%@ page import="java.util.*"%>
<%@ page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%>
<%@ page import="org.apache.commons.fileupload.disk.DiskFileItemFactory"%>
<%@ page import="org.apache.commons.fileupload.*"%>
<%
boolean isMultipart = ServletFileUpload.isMultipartContent(request);

if (!isMultipart)
{
}
else
{
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
List items = null;
try
{
items = upload.parseRequest(request);
}
catch (FileUploadException e)
{
e.printStackTrace();
}

Iterator itr = items.iterator();

while (itr.hasNext())
{
FileItem item = (FileItem) itr.next();

//Get Other Form Fileds Values in this Block
if (item.isFormField())
{
String itemName = item.getFieldName();
String itemValue = item.getString();
String name = "";
if (itemName.equals("userName"))
name = item.getString();

out.println("User Name "+name);
}
//Get File type Values Here, it could be one or multiple File
else
{
try
{
String itemName = item.getName();

//userFieldName is what u provided in html file
String userFieldName = item.getFieldName();

if(itemName != null)
{
if(itemName.equals(""))
{
//If Nothing Uploaded
out.println("No File Uploaded");
}
else
{
//Provide Destination Folder, Where Uploaded File to be saved
boolean folderMade = (new File("d:/UploadedFileFolder")).mkdirs();

// This is required to filter out file name from complete file path.
int idx = itemName.lastIndexOf("\\");

String filename = "";

if(idx > -1)
{
//in case of IE, it sends complete path. Hence only file name must be filtered out.
idx=idx+1;
filename = itemName.substring(idx);
}
else
{
//in case of other borwsers, its just filename
filename = itemName;
}

File savedFile = new File("d:/UploadedFileFolder/"+filename);
item.write(savedFile);

//Get path of the saved file
String path = savedFile.getPath();

out.println("File Uploaded Sucessfully "+path);

}
}
}//try
catch(Exception e)
{
e.printStackTrace();
}
}//else
}//while
}//else
%>