Creating a Batch Service

 To start from scratch, move on to Starting with Spring Initializr.

To skip the basics, do the following:

• Download and unzip the source repository for this guide, or clone it using Git: git clone https://github.com/spring-guides/gs-batch-processing.git
• cd into gs-batch-processing/initial
• Jump ahead to Create a Business Class.

When you finish, you can check your results against the code in gs-batch-processing/complete.

Business Data

Typically, your customer or a business analyst supplies a spreadsheet. For this simple example, you can find some made-up data in src/main/resources/sample-data.csv:

Jill,Doe
Joe,Doe
Justin,Doe
Jane,Doe
John,Doe

This spreadsheet contains a first name and a last name on each row, separated by a comma. This is a fairly common pattern that Spring can handle without customization.

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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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Spring Security Overview

Spring Security is a powerful and highly customizable authentication and access-control framework. It is the de-facto standard for securing Spring-based applications.

Spring Security is a framework that focuses on providing both authentication and authorization to Java applications. Like all Spring projects, the real power of Spring Security is found in how easily it can be extended to meet custom requirements

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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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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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Connecting your Angular 2 App to your Java EE Backend

1-Introduction

You’ve been developing in Java EE all this time, but you’re tired of using JSF, or perhaps even Struts, and want to move to something more modern for your front end? Angular 2 is a perfect fit, and with the recent release of Angular 2 GA, now is the ideal time to make the move! Besides being easier to develop and maintain, an Angular 2 application allows you to take advantage of the huge improvements in browser technology over the last few years, and all the goodness that the modern web brings.

Broad Strokes

We will be working with two separate applications, a Java EE back-end app, and an Angular 2 front-end app, avoiding a mixing of concerns in a single project. Source for both projects is provided, so in this article we display and highlight source only for key concepts – you can download the projects to look at more detail, or run them locally.

Key technologies:

• JPA: Our sample Java EE application uses JPA to access data from a database.
• REST: We expose the table data via REST web services using Jersey – the reference implementation for the JAX-RS spec.
• RxJS: Our Angular 2 app uses RxJS to communicate with the web services.
  

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Error - Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)

Error:

Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.repository.repositories.UserRepository com.service.UserService.repository; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:305)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:301)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:196)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:835)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:446)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:328)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4853)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5314)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.repository.repositories.UserRepository com.service.UserService.repository; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:571)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
... 22 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:236)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1143)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getSingletonFactoryBeanForTypeCheck(AbstractAutowireCapableBeanFactory.java:865)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryBean(AbstractAutowireCapableBeanFactory.java:796)
at org.springframework.beans.factory.support.AbstractBeanFactory.isTypeMatch(AbstractBeanFactory.java:543)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:447)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:423)
at org.springframework.beans.factory.BeanFactoryUtils.beanNamesForTypeIncludingAncestors(BeanFactoryUtils.java:220)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1177)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1116)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:543)
... 24 more

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Comparsion: Struts 2 vs Spring 3 MVC

Apache Struts 2 and Spring MVC are two of the most popular Java web frameworks today. I’ve used both APIs extensively and wanted to share a quick comparison.

In Struts, the object that handles a request and routes it for processing is called an Action. In Spring MVC, that object is referred to as a Controller. Actions and Controllers are pretty much the same thing – they take input, process it, and return some sort of response.

The one major design difference is that by default, Struts 2 Actions are newly instantiated every time a request is made, whereas in Spring MVC the default behavior is to act as a Singleton. Spring MVC Controllers are created once and held in memory/shared across all requests. Note, you can change this behavior (scope) to request or session but we’ll talk about that later. This is a major difference to keep in mind when designing applications that need to be thread-safe, database oriented, or other share-able transactions.

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Consuming a RESTful Web Service with Spring for Android

This Getting Started guide walks you through the process of building an application that uses Spring for Android's RestTemplate to consume a Spring MVC-based RESTful web service.

Compile và chạy ứng dụng rest server

You will build an Android client that consumes a Spring-based RESTful web service. Specifically, the client will consume the service created in Building a RESTful Web Servce.

Chạy spring boot rest: java -jar gs-rest-service-0.1.0.jar

The Android client will be accessed through an Android emulator, and will consume the service accepting requests at:

http://192.168.1.3:8080/greeting

The service will respond with a JSON representation of a greeting:

{"id":1,"content":"Hello, World!"}

The Android client will render the ID and content into a view.

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Spring for Android Showcase

Introduction

This showcase includes an Android client and a Spring MVC server. Together these illustrate the interaction of the client and server when using Spring for Android. This Android project requires set up of the Android SDK. See the main README at the root of this repository for more information about configuring your environment.

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