Hadoop Library is imported but cannot set the “get” method in FyleSystem

I'm trying to setting up a call to HDFS to get a file from it using FileSystem to do so:

I'm trying to setting up a call to HDFS to get a file from it using FileSystem to do so:

FileSystem fs = new FileSystem.get(new URI.create(uri), conf);

But I getting this two errors even so I called all the libraries

    Error:(46, 39) java: cannot find symbol
    symbol:   class get
    location: class org.apache.hadoop.fs.FileSystem
Error:(46, 47) java: cannot find symbol
symbol:   method create(java.lang.String)
location: class org.apache.commons.httpclient.URI

This is for hadoop 2.7.7 version. I already tried imported the hole library org.apache.hadoop.fs.;but still the method get and create is not there when I'm trying to use them in the line as follow: FileSystem fs = new FileSystem.get(URI.create(usi), conf)

import org.apache.commons.httpclient.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;

public class Test {
public static void main(String []args) {

String uri = "hdfs://localhost:9000/data.json";
Configuration conf = new Configuration();

//cannot find symbol get
//Cannot find symbol create
FileSystem fs = new FileSystem.get(new URI.create(uri), conf);

InputStream in = null;

try {
    in = fs.open(new Path(uri));
    IOUtils.copyBytes(in, System.out, 4096, false);
} catch (IOException e) {
    e.printStackTrace();
} finally {
    IOUtils.closeStream(in);
}

}
}

And here is my POM.xml file:

    <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.boeing.bedl</groupId>
<artifactId>IngestionData</artifactId>
<version>1.0-SNAPSHOT</version>

<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>2.7.7</version>
</dependency>

&lt;dependency&gt;
    &lt;groupId&gt;org.apache.hadoop&lt;/groupId&gt;
    &lt;artifactId&gt;hadoop-yarn-common&lt;/artifactId&gt;
    &lt;version&gt;2.7.7&lt;/version&gt;
&lt;/dependency&gt;

&lt;dependency&gt;
    &lt;groupId&gt;org.apache.hadoop&lt;/groupId&gt;
    &lt;artifactId&gt;hadoop-mapreduce-client-core&lt;/artifactId&gt;
    &lt;version&gt;2.7.7&lt;/version&gt;
&lt;/dependency&gt;

&lt;dependency&gt;
    &lt;groupId&gt;org.apache.hadoop&lt;/groupId&gt;
    &lt;artifactId&gt;hadoop-mapreduce-client-common&lt;/artifactId&gt;
    &lt;version&gt;2.7.7&lt;/version&gt;
&lt;/dependency&gt;

</dependencies>
</project>


Hadoop vs Spark | Hadoop MapReduce vs Spark

Hadoop vs Spark | Hadoop MapReduce vs Spark

🔥Intellipaat Big Data Hadoop Course: https://intellipaat.com/big-data-hadoop-training/ In this video on Hadoop vs Spark you will understand about the top Big...

In this video on Hadoop vs Spark you will understand about the top Big Data solutions used in the IT industry, and which one should you use for better performance. So in this Hadoop MapReduce vs Spark comparison some important parameters have been taken into consideration to tell you the difference between Hadoop and Spark also which one is preferred over the other in certain aspects in detail.

Why Hadoop is important

Big data hadoop is one of the best technological advances that is finding increased applications for big data and in a lot of industry domains. Data is being generated hugely in each and every industry domain and to process and distribute effectively hadoop is being deployed everywhere and in every industry.

How to import an existing Maven project into IntelliJ IDEA?

How to import an existing Maven project into IntelliJ IDEA?

This tutorial explains how to import an existing Maven project into IntelliJ IDEA and how to create a running configuration for a Maven goal. This is useful, for example, when using the Jetty Maven plugin that allows you to quickly deploy and run a Java web application using this popular server.

This tutorial explains how to import an existing Maven project into IntelliJ IDEA and how to create a running configuration for a Maven goal. This is useful, for example, when using the Jetty Maven plugin that allows you to quickly deploy and run a Java web application using this popular server.

Maven is a project management tool that goes beyond dependency management. See Learning Maven Concepts to learn more.

Download an Existing Maven Project

This tutorial uses a Maven archetype that generates a web application with a preconfigured Jetty Maven Plugin in it:

mvn -B archetype:generate -DarchetypeGroupId=com.vaadin -DarchetypeArtifactId=vaadin-archetype-application -DarchetypeVersion=LATEST -DgroupId=org.test -DartifactId=webapp -Dversion=1.0-SNAPSHOT

NOTE: If you prefer, you can generate a ZIP file with the project at https://vaadin.com/start/latest or https://start.vaadin.com. Make sure you select the Plain Java Servlet option before downloading the project.

The project should include a directory with a Maven project in it:

NOTE: You need Node.js installed on your computer to compile the example application.

Import the Project

There are several ways to import a Maven project in IntelliJ IDEA. The most common approach is to open the pom.xml file directly. You can do it in the welcome screen by clicking Open:

NOTE: Import Project gives you more options to tweak the import process. However, this is out of the scope of this tutorial.

Select the pom.xml file of the Maven project you want to import and click Open as Project.

NOTE: The welcome window is only shown when you close all projects in IntelliJ IDEA. If you don’t want to close your currently opened projects, you can select File > Open on the menu instead.

Running Maven Goals

IntelliJ IDEA has excellent integration with Maven. You can run common commands such as mvn install or mvn jetty:runwithout having to leave the IDE.

Open the Maven view by clicking the corresponding option on the left side of the IntelliJ IDEA window:

This view shows all the available Maven projects and their build phases and build goals. Let’s say you want to run mvn install. To do that, expand the project tree in the Maven view to show the corresponding lifecycle phase and then double-click install:

You’ll see how IntelliJ IDEA executes the install build phase (and all the previous phases in the Maven’s default lifecycle) that downloads dependencies and copies the generated artifacts into your local Maven repository, among other things.

You can use a similar approach to run any Maven goal. For example, you can double-click the jetty:run goal in the Plugins sub-tree to deploy and run the web application implemented in the project you imported. Similarly, if you are using Spring, you can double-click spring-boot:run to run the application.

Creating a Running Configuration

Since using the jetty:run goal could be a frequent task during the development of a Java web application, you may prefer to create a running configuration for it.

A running configuration is a shortcut to run a specific task from within the IDE. Let’s create a running configuration for the jetty:run Maven goal to make it simpler to run the web application.

Right-click the jetty:run option in the Maven view and select Create 'webapp [jetty:run]':

For simplicity, change the name of the configuration to Run on Jetty and click OK:

NOTE: If you are using a multi-module Maven project, make sure you select the correct module when creating the running configuration.

You should see the new option on the top right corner of IntelliJ IDEA:

Now you can deploy and run the web application by clicking the run (or the debug) icon in the toolbar:

NOTE: If you use the Vaadin project used in the tutorial, you can invoke the web application at http://localhost:8080.

That’s it. Now you can use IntelliJ IDEA to develop your Maven application!

JPA with Eclipse and MySQL: Using Java Configuration

JPA with Eclipse and MySQL: Using Java Configuration

In this tutorial, we learn more about the Java Persistence API and how to effectively configure it with EclipseLink and MySQL.

The** Java Persistence API** is a standard specification for ORM (Object Relational Mapping) implementations. Also, it shows how to define a PLAIN OLD JAVA OBJECT (POJO) as an entity and how to manage entities with relations.

Key JPA Entities

**1.) **<strong>EntityManagerFactory</strong>: This is a factory class of EntityManager. It creates and manages multiple EntityManager instances.

**2.) **<strong>EntityManger</strong>: This interface manages the persistence operations on entities.

**3.) **<strong>Entity</strong>: Entities are the persistence objects, stores as records in the database.

**4.) **<strong>EntityTransaction</strong>: It has a one-to-one relationship with EntityManager. For each EntityManager, operations are maintained by EntityTransaction class.

**5.) **<strong>Persistence</strong>: This class contains static methods used to obtain a EntityManagerFactory instance.

**6.) **<strong>Query</strong>: This interface is implemented by each JPA vendor to obtain relational objects that meet the criteria.

Now, let us start our JPA implementations with an example:

Required Maven dependencies:

<dependencies>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>eclipselink</artifactId>
<version>2.7.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.40</version>
</dependency>
</dependencies>

Here, to achieve persistence in the application, we need to introduce the persistence.xml, which has to be located in the META-INF directory in the project classpath.

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="JPATest"
transaction-type="RESOURCE_LOCAL">
<class><!-- Entity Class Name --></class>
</persistence-unit>
</persistence>

Here, the persistence unit name must be unique. Also, we can add multiple persistence-units for different units. The transaction type for this persistence unit is RESOURCE_LOCAL.

There are two types of transactions:

  • JTA: The transactions will be managed by the Application Server
  • RESOURCE_LOCAL: The transaction will be managed by the JPA Provider Implementation in use.

Also, specify the class name for entities in this configuration file. There is one more configuration used for the database connection. But for dynamic configuration of database connection, we add that configuration in Java code instead of this XML file.

EntityManager:

public class JpaEntityManager {
private EntityManagerFactory emFactoryObj;
private final String PERSISTENCE_UNIT_NAME = "JPATest";
private final Map<String, String> properties=new HashMap<String, String>();


// This Method Is Used To Retrieve The 'EntityManager' Object
public EntityManager getEntityManager() {

String url = String.format("%s/%s", DBConstants.DB_HOST, DBConstants.DB_NAME);

properties.put("javax.persistence.jdbc.driver",DBConstants.DB_DRIVER);
properties.put("javax.persistence.jdbc.url", url);
properties.put("javax.persistence.jdbc.user", DBConstants.DB_USER);
properties.put("javax.persistence.jdbc.password",DBConstants.DB_PASSWORD);
properties.put("useSSL", DBConstants.DB_USE_SSL);
properties.put("requireSSL", DBConstants.DB_REQUIRED_SSL);
properties.put("serverTimezone",DBConstants.DB_SERVER_TIMEZONE);

emFactoryObj = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME,properties);

return emFactoryObj.createEntityManager();
}
}

Here, you have to add your database related configuration like drive class name, hostname, database name, username, password, etc.

Database schema:

CREATE TABLE user (
  id INTEGER NOT NULL,
  name VARCHAR(255) NOT NULL,  
  age VARCHAR(100) NOT NULL,
  PRIMARY KEY(id)
);

Entity:

Here are some annotations used for JPA implementation.

1.) @Entity: to mark the java class as an entity.

2.) @Table: to specify the table to which this entity class maps.

3.) @Id: to identify a row uniquely (JPA Primary Key).

4.) @Column: to specify the mapped column for a persistent property or field.

**5. **<strong>JPARepository</strong>: used to perform database-related operations.

public class JpaRepository<T, ID> implements AutoCloseable {

private final Class<T> typeParameterClass;
protected EntityManager entityManager;

public JpaRepository(Class<T> typeParameterClass) {
JpaEntityManager dbEntityManager = new JpaEntityManager();
entityManager = dbEntityManager.getEntityManager();
this.typeParameterClass = typeParameterClass;
}
/**
 * Save an entity.
 * @param entity
 * @return the saved entity
 */
public <S extends T> S save(S entity) {
entityManager.getTransaction().begin();
entityManager.persist(entity);
entityManager.getTransaction().commit();
return entity;
}
/**
 * merge an entity.
 *
 * @param entity
 * @return the saved entity
 */
public <S extends T> S merge(S entity) {
entityManager.getTransaction().begin();
entityManager.merge(entity);
entityManager.getTransaction().commit();
return entity;
}
/**
 * Delete an entity
 * 
 * @param id
 */
public void delete(ID id) {
entityManager.remove(id);
}
/**
 * Returns a reference to the entity with the given identifier.
 * 
 * @param id
 * @return
 */
public T findById(ID id) {
T t = entityManager.find(typeParameterClass, id);
return t;
}
/**
 * get single result
 * 
 * @param q
 * @return
 */
public Optional<T> getSingleResult(CriteriaQuery<T> q) {

try {
return Optional.ofNullable(entityManager.createQuery(q).getSingleResult());
} catch (RuntimeException e) {
return Optional.empty();
}
}
/**
 * get single result
 * 
 * @param q
 * @return
 */
public Optional<List<T>> getResultList(CriteriaQuery<T> q) {
try {
return Optional.ofNullable(entityManager.createQuery(q).getResultList());
} catch (RuntimeException e) {
return Optional.empty();
}
}
/**
 * used to close entity manager obj
 */
public void close() {
entityManager.clear();
entityManager.close();
}
}

You can also use JPA Criteria API queries, which provide an alternative way for defining JPA queries and is mainly useful for building dynamic queries whose exact structure is only known at runtime.

Now, all configuration is done. So, let us start to test this application.

public class JPADemo {

public static void main(String[] args) {
User user=new User();
user.setId(1);
user.setAge(20);
user.setName("Abc");

try(JpaRepository userJpaRepository=new JpaRepository<BlenderMaster, Long>(BlenderMaster.class)){
userJpaRepository.save(user);
}catch (Exception e) {
e.printStackTrace();
}
}
}

Here, we added the JPA Repository resource in a try catch, so resource will be closed automatically after use. After running this application, one new user entry will be added in the MySQL database.

Thanks For Visiting, Keep Visiting. If you liked this post, share it with all of your programming buddies!

Further reading

Java Programming Masterclass for Software Developers

JSP, Servlets and JDBC for Beginners: Build a Database App

Java 8 New Features In Simple Way

Java In-Depth: Become a Complete Java Engineer!

Java for Absolute Beginners

Java Programming for Complete Beginners - Learn in 250 Steps

Learn Java Programming Crash Course

Apache Spark for Java Developers