Development Challenge

README.md

@@ -0,0 +1,95 @@
+CSVConverter 0.1.0
+==============
+
+Description
+--------------
+
+Web based application accepting via a form comma separated file
+with the following columns: date, category, employee name, employee address, expense description, pre-tax amount, tax name, and tax amount.
+
+
+After upload, application processes the file, stores data in in-memory relational database
+and displays a table of the total expenses amount per-month represented by the uploaded file.
+
+
+The following assumptions are taken:
+
+
+i.   Columns will always be in that order.
+
+ii.  There will always be data in each column.
+
+iii. There will always be a header line.
+
+
+*Notes:*
+
+*The application allows parallel processing of the files.*
+
+*The data stored in the in-memory database is discarded after the application terminates.*
+
+*The records in the uploaded files are not uniquely identified and are not de-duplicated in the database. This may cause accumulation of the monthly expenses returned by the application when multiple uploads of the same or overlapping data are performed.*
+
+*The previously uploaded copies of the files are cleaned up when application starts.*
+
+
+Build and run instructions
+---------------------------
+
+To **build** the application you will need
+
+JDK 1.8 or later.
+
+Maven 3.0+.
+
+
+To build the application execute:
+
+**mvn clean install**
+
+To create a stand alone application package run:
+
+**mvn package**
+
+(the build JAR file will be located in the target directory.)
+
+
+Both commands must be executed from the root application directory where *pom.xml* file resides.
+
+
+To **run** the application you must have
+
+Java 1.8 or later.
+
+The application requires write access to the local directory.
+
+
+To run with Maven execute:
+
+**mvn spring-boot:run**
+
+from the root application directory.
+
+
+Alternatively to run the pre-packaged JAR file execute:
+
+**java -jar <path>/csvconverter-0.1.0.jar**
+
+
+No preliminary steps are necessary to run the application.
+
+Once launched it can be access with you web browser (tested with Firefox and Safari) under the following URI:
+
+**http://localhost:8080**
+
+
+The application can be terminated from the command line by sending SIGTERM signal with CTRL+C.
+
+
+Implementation notes
+----------------------
+
+I have completed the application within couple of nights and enjoyed every step of its development. I was particularly happy to put hands on Spring Batch projects - something I was planning to do for a while bug have not had a good reason to do it. I believe with Spring Batch and Spring Boot we can quickly build well structured applications separating different concerns and leveraging best OO practices.
+
+My TODOs for the next version would include improved error handling, better Unit Test coverage and separation of data between different
+web session contexts.

pom.xml

@@ -0,0 +1,61 @@
+<?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.wave</groupId>
+    <artifactId>csvconverter</artifactId>
+    <version>0.1.0</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>1.4.3.RELEASE</version>
+    </parent>
+
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-thymeleaf</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-devtools</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-configuration-processor</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-batch</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.hsqldb</groupId>
+            <artifactId>hsqldb</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

src/main/java/com/wave/csvconverter/Application.java

@@ -0,0 +1,33 @@
+package com.wave.csvconverter;
+
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.scheduling.annotation.EnableAsync;
+
+import com.wave.csvconverter.configuration.upload.UploadStorageProperties;
+import com.wave.csvconverter.service.upload.UploadService;
+
+@SpringBootApplication
+@EnableConfigurationProperties(UploadStorageProperties.class)
+@EnableAsync
+public class Application {
+
+	public static void main(String[] args) {
+		SpringApplication.run(Application.class, args);
+	}
+
+	/*
+	 * The bean initialization cleans up all leftover artifacts
+	 * from the previous runs
+	 */
+	@Bean
+	CommandLineRunner init(UploadService uploadService) {
+		return (args) -> {
+            uploadService.deleteAll();
+            uploadService.init();
+		};
+	}
+}

src/main/java/com/wave/csvconverter/configuration/persistence/CSVFileReader.java

@@ -0,0 +1,70 @@
+package com.wave.csvconverter.configuration.persistence;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.batch.core.configuration.annotation.StepScope;
+import org.springframework.batch.item.file.FlatFileItemReader;
+import org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper;
+import org.springframework.batch.item.file.mapping.DefaultLineMapper;
+import org.springframework.batch.item.file.transform.DelimitedLineTokenizer;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.core.io.FileSystemResource;
+import org.springframework.stereotype.Component;
+
+import com.wave.csvconverter.domain.EmployeeExpense;
+
+/*
+ * Custom batch file reader. The read accepts the CSV file name
+ * for reading from the JobParameters.
+ * Each job/reader instance can read its own file to ensure parallel
+ * processing of multiple conversion batches. 
+ */
+@Component
+@StepScope
+public class CSVFileReader extends FlatFileItemReader<EmployeeExpense> {
+
+	private String fileName;
+
+	private static final Logger log = LoggerFactory.getLogger(CSVFileReader.class);
+
+	/*
+	 * The CVS file name is passed to the c'tor
+	 */
+	@Autowired
+	public CSVFileReader(@Value("#{jobParameters['convert.file.name']}") final String fileName) {
+		setFileName(fileName);
+		initiazliazeReader();
+	}
+
+	/*
+	 * The reader is initialized with custom line mapper used to fetch records from
+	 * the CVS file according to the required format
+	 */
+	private void initiazliazeReader() {
+		log.info("Initialize CSV Reader for the file '" + fileName + "'");
+
+		setResource(new FileSystemResource(fileName));
+		setLinesToSkip(1); // first line is title definition
+		setLineMapper(new DefaultLineMapper<EmployeeExpense>() {
+			{
+				setLineTokenizer(new DelimitedLineTokenizer() {
+					{
+						setNames(new String[] { "date", "category", "employee_name", "employee_address",
+								"expense_description", "pretax_amount", "tax_name", "tax_amount" });
+					}
+				});
+				setFieldSetMapper(new BeanWrapperFieldSetMapper<EmployeeExpense>() {
+					{
+						setTargetType(EmployeeExpense.class);
+					}
+				});
+			}
+		});
+	}
+
+	public void setFileName(String fileName) {
+		this.fileName = fileName;
+	}
+
+}

src/main/java/com/wave/csvconverter/configuration/persistence/ConversionBatchConfiguration.java

@@ -0,0 +1,91 @@
+package com.wave.csvconverter.configuration.persistence;
+
+import javax.sql.DataSource;
+
+import org.springframework.batch.core.Job;
+import org.springframework.batch.core.Step;
+import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
+import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
+import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
+import org.springframework.batch.core.launch.JobLauncher;
+import org.springframework.batch.core.launch.support.RunIdIncrementer;
+import org.springframework.batch.core.launch.support.SimpleJobLauncher;
+import org.springframework.batch.core.repository.JobRepository;
+import org.springframework.batch.item.database.BeanPropertyItemSqlParameterSourceProvider;
+import org.springframework.batch.item.database.JdbcBatchItemWriter;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.task.SimpleAsyncTaskExecutor;
+
+import com.wave.csvconverter.domain.EmployeeExpense;
+import com.wave.csvconverter.utils.persistence.JobCompletionNotificationListener;
+
+/*
+ * The class defines batch work-flow for CSV files conversion into RDMS
+ */
+@Configuration
+@EnableBatchProcessing
+public class ConversionBatchConfiguration {
+
+	@Autowired
+	public JobBuilderFactory jobBuilderFactory;
+
+	@Autowired
+	public StepBuilderFactory stepBuilderFactory;
+
+	@Autowired
+	public DataSource dataSource;
+
+	@Autowired
+	public JobRepository jobRepository;
+
+	@Autowired
+	public CSVFileReader fileReader;
+
+	/*
+	 * Override the basic synchronous Job launcher to enable
+	 * asynchronous processing of the Job which would prevent
+	 * web requests timeouts and improve UX
+	 */
+	@Bean
+	public JobLauncher asyncJobLauncher() {
+		SimpleJobLauncher simpleJobLauncher = new SimpleJobLauncher();
+		simpleJobLauncher.setJobRepository(jobRepository);
+		simpleJobLauncher.setTaskExecutor(new SimpleAsyncTaskExecutor());
+		return simpleJobLauncher;
+	}
+
+	/*
+	 * Simple writer definition. The data is written into a default in memory
+	 * relation database. The table is initialized each time the application starts
+	 */
+	@Bean
+	public JdbcBatchItemWriter<EmployeeExpense> writer() {
+		JdbcBatchItemWriter<EmployeeExpense> writer = new JdbcBatchItemWriter<EmployeeExpense>();
+		writer.setItemSqlParameterSourceProvider(new BeanPropertyItemSqlParameterSourceProvider<EmployeeExpense>());
+		writer.setSql(
+				"INSERT INTO employee_expenses (expense_date, category,employee_name,employee_address,expense_description,pretax_amount,tax_name,tax_amount) VALUES (:date, :category, :employee_name, :employee_address, :expense_description, :pretax_amount, :tax_name, :tax_amount)");
+		writer.setDataSource(dataSource);
+		return writer;
+	}
+
+	/*
+	 * Register custom Job completion notification listener which would tell us when
+	 * a conversion Job is done
+	 */
+	@Bean
+	public Job job(JobCompletionNotificationListener listener) {
+		return jobBuilderFactory.get("importEmployeeExpenseJob").incrementer(new RunIdIncrementer()).listener(listener)
+				.flow(step1()).end().build();
+	}
+
+	/*
+	 * Conversion step definition
+	 */
+	@Bean
+	public Step step1() {
+		return stepBuilderFactory.get("step1").<EmployeeExpense, EmployeeExpense>chunk(1).reader(fileReader)
+				.writer(writer()).build();
+	}
+}

src/main/java/com/wave/csvconverter/configuration/upload/UploadStorageProperties.java

@@ -0,0 +1,21 @@
+package com.wave.csvconverter.configuration.upload;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+@ConfigurationProperties("storage")
+public class UploadStorageProperties {
+
+    /**
+     * Root folder location for temporary storage of the uploaded files
+     */
+    private String location = "upload-dir";
+
+    public String getLocation() {
+        return location;
+    }
+
+    public void setLocation(String location) {
+        this.location = location;
+    }
+
+}