Java Standalone method to create a File from an InputStream

This method can be used to save any type of file (image, pdf...) for which you have the InputStream:

 public void createLocalCopy(String localFileName,InputStream iStream) throws IOException{
  OutputStream outStream = new FileOutputStream("C:\\Users\\MYFILE\\"+localFileName);
        try{
        System.out.println("making a local copy="+localFileName);
        byte[] buffer = new byte[1024];
        int len;
        while((len = iStream.read(buffer)) >= 0)
         outStream.write(buffer, 0, len);
        outStream.flush();
        outStream.close();
        iStream.close();
        }catch(Exception e)
        {
         outStream.flush();
         outStream.close();
         iStream.close();
        System.out.println("ERROR IN MAKING LOCAL COPY "+localFileName+", ERROR MSG = "+e.getMessage());
        }
        System.out.println("iStream====="+iStream);
 }

Java Class code to test whether springframework's SimpleJdbcCall is Thread Safe or not

import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.springframework.jdbc.core.simple.SimpleJdbcCall;
import org.springframework.jdbc.datasource.AbstractDriverBasedDataSource;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

import com.sushant.verma.common.dto.UserDto;

public class MyThread implements Runnable{
 private static Logger log=LogManager.getLogger(MyThread.class);
 /**
  * creating Instance Variables
  */
 private UserDto userDto;
 private static SimpleJdbcCall procReaduserDto;
 /**
  * name and password VALUE set at instance level to be used
  */
 private String name="code";
 private String pwd="zila";


 public static void setDataSource(DataSource dataSource) {
  log.debug("Inside setDataSource ");
  /**
   * procReaduserDto Object to be created by the main thread in start to be used by multiple threads
   * as in the case of Spring IOC
   */
  procReaduserDto =new SimpleJdbcCall(dataSource);  
 } 

 public static void main(String [] args) throws Throwable  
 {
  /**
   * calling setDataSource with new dataSource object
   * in the start before starting thread as in Spring IOC
   */
  DataSource dataSource = new DriverManagerDataSource();
  ((DriverManagerDataSource) dataSource).setDriverClassName( "com.mysql.jdbc.Driver");
  ((AbstractDriverBasedDataSource) dataSource).setUrl( "jdbc:mysql://localhost:3306/test");
  ((AbstractDriverBasedDataSource) dataSource).setUsername( "root");
  ((AbstractDriverBasedDataSource) dataSource).setPassword( "admin"); 
  setDataSource(dataSource);

  log.debug("========Creating & Starting Threads===========");
  MyThread obj1 = new MyThread();
  MyThread obj2 = new MyThread();
  new Thread(obj1).start();
  new Thread(obj2).start();
  // main thread is ending here,
  // Thread-0 and Thread-1 continue to run.
 }

 public void run()
 {
  try {
   /**
    * Iterating for 3 times
    */
   for (int i=0; i<3; i++) {
    log.info("************************loop "+i+" begins************************");
    if(Thread.currentThread().getName().equals("Thread-1")){
     /**
      * changing Instance Variable name/pwd value for thread-1 
      */
     setName("wrong_userName");
     setPwd("wrong_password");
    }

    /**
     * calling the readUser method for both the threads with different name/pwd values
     */
    setUserDto(readUser(name, pwd));
    /**
     * Thread-1 should return __isUserValid=false & __getUserExists=0
     * Thread-0 should return __isUserValid=true & __getUserExists=1
     */
    log.info("~~~~~~~~~loop "+i+" ends~~~~~~~~~");
   }
  } catch (Throwable t) { }
 }


 public UserDto readUser(String userEmail,String password) {
  /**
   * procReaduserDto object value should be same as created before the thread starts as to be the case with Spring IOC
   */
  log.debug(" @ readUser with procReaduserDto="+procReaduserDto);
  MyThread.procReaduserDto.withProcedureName("sp_authenticateUser");  

  Map args=new HashMap();  
  args.put("in_userName", userEmail);  
  args.put("in_password", password);  
  @SuppressWarnings("unused")
  Map out = procReaduserDto.execute(args);  

  UserDto userDto = new UserDto();  
  userDto.setUserExists((String) out.get("out_userexists"));  
  String userValid=(String) out.get("out_isuservalid");  
  if(userValid.equals("1"))  
   userDto.setUserValid(true);  
  else  
   userDto.setUserValid(false);  

  return userDto;  
 }

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public String getPwd() {
  return pwd;
 }

 public void setPwd(String pwd) {
  this.pwd = pwd;
 }

 public void setUserDto(UserDto userDto) {
  this.userDto = userDto;
 }

 public UserDto getUserDto() {
  return userDto;
 }


}

How to generate a random alphanumeric word with special characters of variable length

Usually we need to create a random word of some 8+ character to use as a password or an encryption key.

I have recently created this one, though very simple but very effective.

I have tried to replicate the same sequence and run in a loop of 1000000 iteration but with length of 8 characters there were no repetition. Hope the readers would like it.

package in.codeZila.www.utility;

public class RandomWordGenerator {

 public static final String getRandomWord(int length) {
  String chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890!@#$%^&*";
  String rw = "";
  for(int i = 0; i < length; i++) {
   int index = (int) Math.floor(Math.random() * 62);
   rw += chars.charAt(index);
  }

  return rw;
 }
 
 public static void main(String[] args) {
  for(int i=0;i<100;i++){
   String randomPwd=getRandomWord(8);
   System.out.println(randomPwd);
  }
 }
 
}

The Random words generated are :

Please feel free to ask any doubts or clarifications.

How to get the XML String for a DTO (Data transfer object) using XStream

To get the XML for a DTO XStream (com.thoughtworks.xstream.XStream) is used, Download the "xstream-1.4.2.jar" jar : Click Here and add into your lib folder.

The Method which returns the XML for the passed DTO:

public static String getDTOasXML(Object dto){
 XStream xstream = new XStream();
        return xstream.toXML(dto);
}

The UserDto which needs to be converted to XML :

public class UserDto{

 
 private Long userId;

 private String userName;

 private String userEmail;

 public Long getUserId() {
  return userId;
 }

 public void setUserId(Long userId) {
  this.userId = userId;
 }

 public String getUserName() {
  return userName;
 }

 public void setUserName(String userName) {
  this.userName = userName;
 }

 public String getUserEmail() {
  return userEmail;
 }

 public void setUserEmail(String userEmail) {
  this.userEmail = userEmail;
 } 
}

Note: Notice that the fields are private. XStream doesn't care about the visibility of the fields. No getters or setters are needed. Also, XStream does not limit you to having a default constructor.

The Test Class to implement the XStream.toXML() method :

package in.codeZila.test;

import in.codeZila.test.dto.UserDto;
import com.thoughtworks.xstream.XStream;


public class Test{
 
 /**
  * Using XStream method toXML():String to generate the XML for the passed DTO object
  * @param dto
  * @return dto XML as String
  */
 public static String getDTOasXML(Object dto){
  XStream xstream = new XStream();
  /**
   * Now, to make the XML outputted by XStream more concise, 
   * you can create aliases for your custom class names to XML 
   * element names. This is the only type of mapping required to 
   * use XStream and even this is optional.
   * 
   * Note: This is an optional step. Without it XStream would work fine, 
   * but the XML element names would contain the fully qualified name of 
   * each class (including package) which would bulk up the XML a bit.
   */
  xstream.alias("UserDto", UserDto.class);
  return xstream.toXML(dto);
 }
 
 public static void main(String[] args) {
  /**
   * Instantiate the UserDto and set its variables
   */
  UserDto userDto=new UserDto();
  userDto.setUserId(new Long(1));
  userDto.setUserName("CodeZila");
  userDto.setUserEmail("codezila@codezila.in");
  /**
   * Pass the userDto Object created above as getDTOasXML() argument
   */
  String dtoXml=Test.getDTOasXML(userDto);
  System.out.println(dtoXml);
 }
}

The Output XML :

Thats all, how simple XStream is!

Summary:

• Create element name to class name aliases for any custom classes using xstream.alias(String elementName, Class cls); 
• Convert an object to XML using xstream.toXML(Object obj); 
• Convert XML back to an object using xstream.fromXML(String xml);

Your valuable inputs and suggestions are welcomed!

Java Method to copy a folder directory contents from source location to destination location

public void copyDirectory(java.io.File sourceLocation, java.io.File targetLocation) {
 System.out.println("Starting Copying");
 try {
  if (sourceLocation.isDirectory()) {
   if (!targetLocation.exists()) {
    targetLocation.mkdir();
   }

   String[] children = sourceLocation.list();
   for (int i = 0; i < children.length; i++) {
    copyDirectory(new java.io.File(sourceLocation, children[i]),
      new java.io.File(targetLocation, children[i]));
   }
  } 
  else {
   java.io.InputStream in = new java.io.FileInputStream(sourceLocation);
   java.io.OutputStream out = new java.io.FileOutputStream(targetLocation);
   byte[] buf = new byte[1024];
   int len;
   while ((len = in.read(buf)) > 0) {
    out.write(buf, 0, len);
   }
   in.close();
   out.close(); 
  }
 } catch (java.io.IOException e) {
  e.printStackTrace();
  throw new RuntimeException(e);
 }
 System.out.println("Completed Copying");
}

To test this method just create a directory at any location say: (c:/sourceLocation/) with some files in it. And you want to copy all the contents of this directory to a new location say : (d:/targetLocation) which may or may not exist. Then this function will create the target location and copy all the contents from the given source location to the target location. 

 The sample test class to test this method:

public class TestCopyDrectory {

 public static void main(String[] args) {
  copyDirectory(new java.io.File("C:/sourceLocation/"), new java.io.File("D:/targetLocation"));
 }

 public static void copyDirectory(java.io.File sourceLocation, java.io.File targetLocation) {
  System.out.println("Starting Copying");
  try {
   if (sourceLocation.isDirectory()) {
    if (!targetLocation.exists()) {
     targetLocation.mkdir();
    }

    String[] children = sourceLocation.list();
    for (int i = 0; i < children.length; i++) {
     copyDirectory(new java.io.File(sourceLocation, children[i]),
       new java.io.File(targetLocation, children[i]));
    }
   } 
   else {
    java.io.InputStream in = new java.io.FileInputStream(sourceLocation);
    java.io.OutputStream out = new java.io.FileOutputStream(targetLocation);
    byte[] buf = new byte[1024];
    int len;
    while ((len = in.read(buf)) > 0) {
     out.write(buf, 0, len);
    }
    in.close();
    out.close(); 
   }
  } catch (java.io.IOException e) {
   e.printStackTrace();
   throw new RuntimeException(e);
  }
  System.out.println("Completed Copying");
 }

}

Steps to create a dataSource bean in applicationContext.xml in Spring Framework with its properties for jdbc connection string obtained from a properties file

In Spring Framework while creating a dataSource bean in applicationContext.xml, it is required to establish the jdbc connection with the connection properties like driverClassName, url, username, password being defined.

The same can be defined directly with all the property values there itself hard coded like :


But there is a better way, separate the jdbc connection dataSource bean in a seperate xml say dataSource.xml which you can import in the main applicationContext.xml

And it will be even further better if the properties  like driverClassName, url, username, password of jdbc connection string are fetched from a properties file which can be easily changed depending upon the environment without even touching the applicationContext.xml file thus the dependency is removed.

To separate the dataSource bean two files need to be created in src folder (in the same directory as applicationContext.xml):


1) dataSource.xml
2) jdbc.properties


Steps :

1) Inside src folder create a xml file dataSource.xml Paste the following in it :


Here i have used "org.springframework.jdbc.datasource.DriverManagerDataSource" as dataSource class which can be any other datasource class.


2) Inside src folder create a properties file jdbc.properties. Paste the following in it :


The Database connection string is created for mysql for database "TEST"

3) Import the created dataSource.xml in your applicationContext.xml:




That was all, you application is good to go. Got any doubts, feel free to ask/comment.