Jason Thomas

Jason Thomas

1562054439

Web Service Tutorial: Streaming Data with Spring Boot RESTful

In this article, we are going to look at an example to download files using StreamingResponseBody. In this approach, data is processed and written in chunks to the OutputStream.

Streaming data is a radical new approach to sending data to web browsers which provides for dramatically faster page load times. Quite often, we need to allow users to download files in web applications. When the data is too large, it becomes quite a challenge to provide a good user experience.

Spring offers support for asynchronous request processing via StreamingResponseBody. In this approach, an application can write data directly to the response OutputStream without holding up the Servlet container thread. There are a few other methods in Spring to handle asynchronous request processing.

Setting Up Spring Boot Project

Create a sample Spring Boot application. Here is my sample project structure. I have created the project manually, but you could also create using Spring Intializer.

Project structure

Let us add some basic dependencies to Maven POM.

<?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.techshard.streamingresponse</groupId>
    <artifactId>springboot-download</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath />
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
        </dependency>
    </dependencies>
</project>

We will now create a controller and add an API endpoint for download. Here is my complete controller.

package com.techshard.download.controller;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
@RestController
@RequestMapping ("/api")
public class DownloadController {
    private final Logger logger = LoggerFactory.getLogger(DownloadController.class);
    @GetMapping (value = "/download", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<StreamingResponseBody> download(final HttpServletResponse response) {
        response.setContentType("application/zip");
        response.setHeader(
                "Content-Disposition",
                "attachment;filename=sample.zip");
        StreamingResponseBody stream = out -> {
            final String home = System.getProperty("user.home");
            final File directory = new File(home + File.separator + "Documents" + File.separator + "sample");
            final ZipOutputStream zipOut = new ZipOutputStream(response.getOutputStream());
            if(directory.exists() && directory.isDirectory()) {
                try {
                    for (final File file : directory.listFiles()) {
                        final InputStream inputStream=new FileInputStream(file);
                        final ZipEntry zipEntry=new ZipEntry(file.getName());
                        zipOut.putNextEntry(zipEntry);
                        byte[] bytes=new byte[1024];
                        int length;
                        while ((length=inputStream.read(bytes)) >= 0) {
                            zipOut.write(bytes, 0, length);
                        }
                        inputStream.close();
                    }
                    zipOut.close();
                } catch (final IOException e) {
                    logger.error("Exception while reading and streaming data {} ", e);
                }
            }
        };
        logger.info("steaming response {} ", stream);
        return new ResponseEntity(stream, HttpStatus.OK);
    }
}

In this API endpoint, we are reading multiple files from a directory and creating a zip file. We are executing this process within StreamingResponseBody*. It writes data directly to an OutputStream before passing that written information back to the client using aResponseEntity. *This means that the download process will start immediately on the client, while the server is processing and writing data in chunks.

Start the server and test this endpoint using http://localhost:8080/api/download.

When using StreamingResponseBody, it is highly recommended to configure TaskExecutor used in Spring MVC for executing asynchronous requests. TaskExecutor is an interface that abstracts the execution of a Runnable.

Let us configure the TaskExecutor. Here is the AsyncConfiguration class which configures timeout using WebMvcCofigurer and also registers an interceptor that is called when there’s a timeout in case you need some special handling.

package com.techshard.download;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.aop.interceptor.SimpleAsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.AsyncTaskExecutor;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.CallableProcessingInterceptor;
import org.springframework.web.context.request.async.TimeoutCallableProcessingInterceptor;
import org.springframework.web.servlet.config.annotation.AsyncSupportConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import java.util.concurrent.Callable;
@Configuration
@EnableAsync
@EnableScheduling
public class AsyncConfiguration implements AsyncConfigurer {
    private final Logger log = LoggerFactory.getLogger(AsyncConfiguration.class);
    @Override
    @Bean (name = "taskExecutor")
    public AsyncTaskExecutor getAsyncExecutor() {
        log.debug("Creating Async Task Executor");
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(25);
        return executor;
    }
    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new SimpleAsyncUncaughtExceptionHandler();
    }
    /** Configure async support for Spring MVC. */
    @Bean
    public WebMvcConfigurer webMvcConfigurerConfigurer(AsyncTaskExecutor taskExecutor, CallableProcessingInterceptor callableProcessingInterceptor) {
        return new WebMvcConfigurer() {
            @Override
            public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
                configurer.setDefaultTimeout(360000).setTaskExecutor(taskExecutor);
                configurer.registerCallableInterceptors(callableProcessingInterceptor);
                WebMvcConfigurer.super.configureAsyncSupport(configurer);
            }
        };
    }
    @Bean
    public CallableProcessingInterceptor callableProcessingInterceptor() {
        return new TimeoutCallableProcessingInterceptor() {
            @Override
            public <T> Object handleTimeout(NativeWebRequest request, Callable<T> task) throws Exception {
                log.error("timeout!");
                return super.handleTimeout(request, task);
            }
        };
    }
}

Conclusion

Using StreamingResponseBody, we can now stream data easily for highly-concurrent applications. I hope you enjoyed this article. Let me know if you have any comments or suggestion in the comments section below.

The example for this article can be found on GitHub repository.

#web-service #web-development #spring-boot #java #rest

What is GEEK

Buddha Community

Web Service Tutorial: Streaming Data with Spring Boot RESTful
Jason Thomas

Jason Thomas

1562054439

Web Service Tutorial: Streaming Data with Spring Boot RESTful

In this article, we are going to look at an example to download files using StreamingResponseBody. In this approach, data is processed and written in chunks to the OutputStream.

Streaming data is a radical new approach to sending data to web browsers which provides for dramatically faster page load times. Quite often, we need to allow users to download files in web applications. When the data is too large, it becomes quite a challenge to provide a good user experience.

Spring offers support for asynchronous request processing via StreamingResponseBody. In this approach, an application can write data directly to the response OutputStream without holding up the Servlet container thread. There are a few other methods in Spring to handle asynchronous request processing.

Setting Up Spring Boot Project

Create a sample Spring Boot application. Here is my sample project structure. I have created the project manually, but you could also create using Spring Intializer.

Project structure

Let us add some basic dependencies to Maven POM.

<?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.techshard.streamingresponse</groupId>
    <artifactId>springboot-download</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath />
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
        </dependency>
    </dependencies>
</project>

We will now create a controller and add an API endpoint for download. Here is my complete controller.

package com.techshard.download.controller;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
@RestController
@RequestMapping ("/api")
public class DownloadController {
    private final Logger logger = LoggerFactory.getLogger(DownloadController.class);
    @GetMapping (value = "/download", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<StreamingResponseBody> download(final HttpServletResponse response) {
        response.setContentType("application/zip");
        response.setHeader(
                "Content-Disposition",
                "attachment;filename=sample.zip");
        StreamingResponseBody stream = out -> {
            final String home = System.getProperty("user.home");
            final File directory = new File(home + File.separator + "Documents" + File.separator + "sample");
            final ZipOutputStream zipOut = new ZipOutputStream(response.getOutputStream());
            if(directory.exists() && directory.isDirectory()) {
                try {
                    for (final File file : directory.listFiles()) {
                        final InputStream inputStream=new FileInputStream(file);
                        final ZipEntry zipEntry=new ZipEntry(file.getName());
                        zipOut.putNextEntry(zipEntry);
                        byte[] bytes=new byte[1024];
                        int length;
                        while ((length=inputStream.read(bytes)) >= 0) {
                            zipOut.write(bytes, 0, length);
                        }
                        inputStream.close();
                    }
                    zipOut.close();
                } catch (final IOException e) {
                    logger.error("Exception while reading and streaming data {} ", e);
                }
            }
        };
        logger.info("steaming response {} ", stream);
        return new ResponseEntity(stream, HttpStatus.OK);
    }
}

In this API endpoint, we are reading multiple files from a directory and creating a zip file. We are executing this process within StreamingResponseBody*. It writes data directly to an OutputStream before passing that written information back to the client using aResponseEntity. *This means that the download process will start immediately on the client, while the server is processing and writing data in chunks.

Start the server and test this endpoint using http://localhost:8080/api/download.

When using StreamingResponseBody, it is highly recommended to configure TaskExecutor used in Spring MVC for executing asynchronous requests. TaskExecutor is an interface that abstracts the execution of a Runnable.

Let us configure the TaskExecutor. Here is the AsyncConfiguration class which configures timeout using WebMvcCofigurer and also registers an interceptor that is called when there’s a timeout in case you need some special handling.

package com.techshard.download;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.aop.interceptor.SimpleAsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.AsyncTaskExecutor;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.CallableProcessingInterceptor;
import org.springframework.web.context.request.async.TimeoutCallableProcessingInterceptor;
import org.springframework.web.servlet.config.annotation.AsyncSupportConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import java.util.concurrent.Callable;
@Configuration
@EnableAsync
@EnableScheduling
public class AsyncConfiguration implements AsyncConfigurer {
    private final Logger log = LoggerFactory.getLogger(AsyncConfiguration.class);
    @Override
    @Bean (name = "taskExecutor")
    public AsyncTaskExecutor getAsyncExecutor() {
        log.debug("Creating Async Task Executor");
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(25);
        return executor;
    }
    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new SimpleAsyncUncaughtExceptionHandler();
    }
    /** Configure async support for Spring MVC. */
    @Bean
    public WebMvcConfigurer webMvcConfigurerConfigurer(AsyncTaskExecutor taskExecutor, CallableProcessingInterceptor callableProcessingInterceptor) {
        return new WebMvcConfigurer() {
            @Override
            public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
                configurer.setDefaultTimeout(360000).setTaskExecutor(taskExecutor);
                configurer.registerCallableInterceptors(callableProcessingInterceptor);
                WebMvcConfigurer.super.configureAsyncSupport(configurer);
            }
        };
    }
    @Bean
    public CallableProcessingInterceptor callableProcessingInterceptor() {
        return new TimeoutCallableProcessingInterceptor() {
            @Override
            public <T> Object handleTimeout(NativeWebRequest request, Callable<T> task) throws Exception {
                log.error("timeout!");
                return super.handleTimeout(request, task);
            }
        };
    }
}

Conclusion

Using StreamingResponseBody, we can now stream data easily for highly-concurrent applications. I hope you enjoyed this article. Let me know if you have any comments or suggestion in the comments section below.

The example for this article can be found on GitHub repository.

#web-service #web-development #spring-boot #java #rest

Were  Joyce

Were Joyce

1623380652

Spring Boot With Spring Data JPA: SB CRUD [Video]

Learn how to use Spring Boot with Spring Data JPA with this Spring Boot CRUD example using both RESTful APIs and JPA. Let’s get started!

In the video below, we take a closer look at the Spring Boot With Spring Data JPA | Spring Boot CRUD Example with RESTful APIs and JPA. Let’s get started!

#tutorial #spring boot #video #jpa #restful api #spring boot tutorial #restful web service

Roberta  Ward

Roberta Ward

1595344320

Wondering how to upgrade your skills in the pandemic? Here's a simple way you can do it.

Corona Virus Pandemic has brought the world to a standstill.

Countries are on a major lockdown. Schools, colleges, theatres, gym, clubs, and all other public places are shut down, the country’s economy is suffering, human health is on stake, people are losing their jobs and nobody knows how worse it can get.

Since most of the places are on lockdown, and you are working from home or have enough time to nourish your skills, then you should use this time wisely! We always complain that we want some ‘time’ to learn and upgrade our knowledge but don’t get it due to our ‘busy schedules’. So, now is the time to make a ‘list of skills’ and learn and upgrade your skills at home!

And for the technology-loving people like us, Knoldus Techhub has already helped us a lot in doing it in a short span of time!

If you are still not aware of it, don’t worry as Georgia Byng has well said,

“No time is better than the present”

– Georgia Byng, a British children’s writer, illustrator, actress and film producer.

No matter if you are a developer (be it front-end or back-end) or a data scientisttester, or a DevOps person, or, a learner who has a keen interest in technology, Knoldus Techhub has brought it all for you under one common roof.

From technologies like Scala, spark, elastic-search to angular, go, machine learning, it has a total of 20 technologies with some recently added ones i.e. DAML, test automation, snowflake, and ionic.

How to upgrade your skills?

Every technology in Tech-hub has n number of templates. Once you click on any specific technology you’ll be able to see all the templates of that technology. Since these templates are downloadable, you need to provide your email to get the template downloadable link in your mail.

These templates helps you learn the practical implementation of a topic with so much of ease. Using these templates you can learn and kick-start your development in no time.

Apart from your learning, there are some out of the box templates, that can help provide the solution to your business problem that has all the basic dependencies/ implementations already plugged in. Tech hub names these templates as xlr8rs (pronounced as accelerators).

xlr8rs make your development real fast by just adding your core business logic to the template.

If you are looking for a template that’s not available, you can also request a template may be for learning or requesting for a solution to your business problem and tech-hub will connect with you to provide you the solution. Isn’t this helpful 🙂

Confused with which technology to start with?

To keep you updated, the Knoldus tech hub provides you with the information on the most trending technology and the most downloaded templates at present. This you’ll be informed and learn the one that’s most trending.

Since we believe:

“There’s always a scope of improvement“

If you still feel like it isn’t helping you in learning and development, you can provide your feedback in the feedback section in the bottom right corner of the website.

#ai #akka #akka-http #akka-streams #amazon ec2 #angular 6 #angular 9 #angular material #apache flink #apache kafka #apache spark #api testing #artificial intelligence #aws #aws services #big data and fast data #blockchain #css #daml #devops #elasticsearch #flink #functional programming #future #grpc #html #hybrid application development #ionic framework #java #java11 #kubernetes #lagom #microservices #ml # ai and data engineering #mlflow #mlops #mobile development #mongodb #non-blocking #nosql #play #play 2.4.x #play framework #python #react #reactive application #reactive architecture #reactive programming #rust #scala #scalatest #slick #software #spark #spring boot #sql #streaming #tech blogs #testing #user interface (ui) #web #web application #web designing #angular #coronavirus #daml #development #devops #elasticsearch #golang #ionic #java #kafka #knoldus #lagom #learn #machine learning #ml #pandemic #play framework #scala #skills #snowflake #spark streaming #techhub #technology #test automation #time management #upgrade

Were  Joyce

Were Joyce

1624248441

Spring Annotations for REST Services

Here over this article, we are discussing different REST specific annotations in Spring.

@Controller

We can annotate classic controllers with the _@Controller_ annotation. This is simply a specialization of the _@Component_ class, which allows us to auto-detect implementation classes through classpath scanning.

We typically use @Controller_ it in combination with an _@RequestMapping_ annotation for request handling methods_.

@RestController

_@RestController_ is a specialized version of the controller. It includes the _@Controller_ and _@ResponseBody_ annotations, and as a result, simplifies the controller implementation.

#spring #java #spring-boot #spring annotations for rest services #rest services #spring annotations

Were  Joyce

Were Joyce

1620736200

Introduction to Spring Boot and JDBCTemplate: Refactoring to SpringData JPA

Introduction to Spring Boot and JDBCTemplate: Refactoring to SpringData JPA.

Refactoring is the process of modifying a software system without changing its desirable behavior. It was necessary to have an application integrated with the relational database using the Spring JDBC Template in the first parts. The Spring JDBC Template is a powerful tool that facilitates productivity. However, there is a way to simplify the code even further with Spring Data JPA. The purpose of this post is to refactor the project to use Spring Data JPA.

Spring Data JPA, part of the larger Spring Data family, makes it easy to implement JPA-based repositories easily. This module deals with enhanced support for JPA-based data access layers. It makes it easier to build Spring-powered applications that use data access technologies.

A safe code refactoring requires the use of tests to ensure that the compartment is not changed. The use of tests, fortunately, is adopted as a minimum standard, including several methodologies such as TDD that preach the creation of tests at the beginning of the development process.

#java #tutorial #spring #spring data #java tutorial #spring tutorial #spring data jpa