Spring batch introduction

Spring Batch is a lightweight, comprehensive batch framework designed to enable the development of robust batch applications vital for the daily operations of enterprise systems. Spring Batch builds upon the characteristics of the Spring Framework that people have come to expect (productivity, POJO-based development approach, and general ease of use), while making it easy for developers to access and leverage more advance enterprise services when necessary. Spring Batch is not a scheduling framework. There are many good enterprise schedulers (such as Quartz, Tivoli, Control-M, etc.) available in both the commercial and open source spaces. It is intended to work in conjunction with a scheduler, not replace a scheduler. 

Spring Batch is also a minimalistic framework to run batch processing applications. It provides reusable functions that are essential in processing large volumes of records, including logging/tracing, transaction management, job processing statistics, job restart, skip, and resource management. It also provides more advanced technical services and features that will enable extremely high-volume and high-performance batch jobs through optimization and partitioning techniques. Simple as well as complex, high-volume batch jobs can leverage the framework in a highly scalable manner to process significant volumes of information.

Spring Batch provides reusable functions that are essential in processing large volumes of records, including logging/tracing, transaction management, job processing statistics, job restart, skip, and resource management. It also provides more advanced technical services and features that enable extremely high-volume and high performance batch jobs through optimization and partitioning techniques. Spring Batch can be used in both simple use cases (such as reading a file into a database or running a stored procedure) as well as complex, high volume use cases (such as moving high volumes of data between databases, transforming it, and so on). High-volume batch jobs can leverage the framework in a highly scalable manner to process significant volumes of information.

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Beginning Amazon DynamoDB

What Is Amazon DynamoDB?

Amazon DynamoDB is a fully managed NoSQL database service that provides fast and predictable performance with seamless scalability. 

NoSQL is a term used to describe nonrelational database systems that are highly available, scalable, and optimized for high performance. Instead of the relational model, NoSQL databases (like DynamoDB) use alternate models for data management, such as key-value pairs or document storage. For more information, see http://aws.amazon.com/nosql.

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MyBatis introduction

 MyBatis is a Java persistence framework that couples objects with stored procedures or SQL statements using an XML descriptor or annotations.

MyBatis is free software that is distributed under the Apache License 2.0.

MyBatis is a fork of iBATIS 3.0 and is maintained by a team that includes the original creators of iBATIS. 

MyBatis is a first class persistence framework with support for custom SQL, stored procedures and advanced mappings. MyBatis eliminates almost all of the JDBC code and manual setting of parameters and retrieval of results. MyBatis can use simple XML or Annotations for configuration and map primitives, Map interfaces and Java POJOs (Plain Old Java Objects) to database records

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Apache Wicket 9 news

 With emerging of ReactJS and  Angular and Microservices, Apache Wicket framework seems darkly because many people think that only ReactJS, Angular, VueJS can work with Microservices. But apache wicket is also a FrontEnd framework and can communicate with Microservices over internet by JSON format data exchange and It is still safely, more stronger. Following is the news from https://wicket.apache.org site:

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Spring Boot + React Redux and MySQL CRUD example

This article will build React Redux Http Client & Spring Boot Server example that uses Spring Data JPA to interact with MySQL database and React as a front-end technology to make request and receive response.
Technologies
– Java 1.8
– Maven 3.3.9
– Spring Tool Suite 3.9.0.RELEASE
– Spring Boot 2.0.1.RELEASE
– Webpack 4.4.1
– React 16.3.0
– Redux 3.7.2
– React Redux 5.0.7
– axios 0.18.0
– MySQL 5.7.16

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React.js and Spring Data REST - Basic Features

Spring Data REST provides backend functionality
React has sophisticated features to build an easy-to-grok UI.

• Spring Data REST provides a fast way to build hypermedia-powered repositories.
• React is Facebook’s solution to efficient, fast, and easy-to-use views in the land of JavaScript.

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Java Concurrency

1. Java Concurrency from docs.oracle.com
Computer users take it for granted that their systems can do more than one thing at a time. They assume that they can continue to work in a word processor, while other applications download files, manage the print queue, and stream audio. Even a single application is often expected to do more than one thing at a time. For example, that streaming audio application must simultaneously read the digital audio off the network, decompress it, manage playback, and update its display. Even the word processor should always be ready to respond to keyboard and mouse events, no matter how busy it is reformatting text or updating the display. Software that can do such things is known as concurrent software.
The Java platform is designed from the ground up to support concurrent programming, with basic concurrency support in the Java programming language and the Java class libraries. Since version 5.0, the Java platform has also included high-level concurrency APIs. This lesson introduces the platform's basic concurrency support and summarizes some of the high-level APIs in the java.util.concurrent packages.

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Spring Boot REST + Angular 2 + JPA + Hibernate + MySQL CRUD Example

We will create a REST web service application using Spring Boot and a client application using Angular 2. REST web service will expose methods for create, read, update and delete operation. The Angular application will use Angular Http API for CRUD operation. If our client application is running on different domain from web service domain, then the Spring Boot web service controller will configure client domain URL using @CrossOrigin annotation to handle Cross-Origin-Resource-Sharing (CORS). In our Spring Boot application, we will configure database using application.properties file. To interact with database we will use JPA EntityManager.

There are back-end application using spring-boot rest api and front-end application using Angular 2.

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JPA Criteria API

Using the Criteria API to Create Queries

The Criteria API is used to define queries for entities and their persistent state by creating query-defining objects. Criteria queries are written using Java programming language APIs, are typesafe, and are portable. Such queries work regardless of the underlying data store.

The following topics are addressed here:

• Overview of the Criteria and Metamodel APIs
• Using the Metamodel API to Model Entity Classes
• Using the Criteria API and Metamodel API to Create Basic Typesafe Queries

0.1 Overview of the Criteria and Metamodel APIs

Similar to JPQL, the Criteria API is based on the abstract schema of persistent entities, their relationships, and embedded objects. The Criteria API operates on this abstract schema to allow developers to find, modify, and delete persistent entities by invoking Java Persistence API entity operations. The Metamodel API works in concert with the Criteria API to model persistent entity classes for Criteria queries.

The Criteria API and JPQL are closely related and are designed to allow similar operations in their queries. Developers familiar with JPQL syntax will find equivalent object-level operations in the Criteria API.

The following simple Criteria query returns all instances of the Pet entity in the data source:

EntityManager em = ...;
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Pet> cq = cb.createQuery(Pet.class);
Root<Pet> pet = cq.from(Pet.class);
cq.select(pet);
TypedQuery<Pet> q = em.createQuery(cq);
List<Pet> allPets = q.getResultList();

The equivalent JPQL query is

SELECT p
FROM Pet p

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JPA Select Statements and NamedQuery

Select Statements

A select query has six clauses: SELECT, FROM, WHERE, GROUP BY, HAVING, and ORDER BY. The SELECT and FROM clauses are required, but the WHERE, GROUP BY, HAVING, and ORDER BY clauses are optional. Here is the high-level BNF syntax of a query language select query:

     Note: some of the terms referred to in this chapter.

• Abstract schema: The persistent schema abstraction (persistent entities, their state, and their relationships) over which queries operate. The query language translates queries over this persistent schema abstraction into queries that are executed over the database schema to which entities are mapped.
• Abstract schema type: The type to which the persistent property of an entity evaluates in the abstract schema. That is, each persistent field or property in an entity has a corresponding state field of the same type in the abstract schema. The abstract schema type of an entity is derived from the entity class and the metadata information provided by Java language annotations.
• Backus-Naur Form (BNF): A notation that describes the syntax of high-level languages. The syntax diagrams in this chapter are in BNF notation.
• Navigation: The traversal of relationships in a query language expression. The navigation operator is a period.
• Path expression: An expression that navigates to an entity's state or relationship field.
• State field: A persistent field of an entity.
• Relationship field: A persistent field of an entity whose type is the abstract schema type of the related entity.

QL_statement ::= select_clause from_clause 
  [where_clause][groupby_clause][having_clause][orderby_clause]

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