Spring Batch `FlatFileItemReader` – 读取 CSV 示例

原文： https://howtodoinjava.com/spring-batch/flatfileitemreader-read-csv-example/

学习使用FlatFileItemReader类从文件系统或资源文件夹中读取 CSV 文件。

项目结构

在这个项目中，我们将学习：

1. 从input/inputData.csv读取 CSV 文件。
2. 将数据写入控制台。

项目结构

使用FlatFileItemReader读取 CSV

您需要使用FlatFileItemReader从 CSV 文件中读取行。

BatchConfig.java

@Bean
public FlatFileItemReader<Employee> reader() 
{
    //Create reader instance
    FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
    //Set input file location
    reader.setResource(new FileSystemResource("input/inputData.csv"));
    //Set number of lines to skips. Use it if file has header rows.
    reader.setLinesToSkip(1);     
    //Configure how each line will be parsed and mapped to different values
    reader.setLineMapper(new DefaultLineMapper() {
        {
            //3 columns in each row
            setLineTokenizer(new DelimitedLineTokenizer() {
                {
                    setNames(new String[] { "id", "firstName", "lastName" });
                }
            });
            //Set values in Employee class
            setFieldSetMapper(new BeanWrapperFieldSetMapper<Employee>() {
                {
                    setTargetType(Employee.class);
                }
            });
        }
    });
    return reader;
}

inputData.csv

id,firstName,lastName
1,Lokesh,Gupta
2,Amit,Mishra
3,Pankaj,Kumar
4,David,Miller

将读取的行写入控制台

创建实现ItemWriter接口的ConsoleItemWriter类。

ConsoleItemWriter.java

import java.util.List;
import org.springframework.batch.item.ItemWriter;
public class ConsoleItemWriter<T> implements ItemWriter<T> { 
    @Override 
    public void write(List<? extends T> items) throws Exception { 
        for (T item : items) { 
            System.out.println(item); 
        } 
    } 
}

使用ConsoleItemWriter作为编写器。

BatchConfig.java

@Bean
public ConsoleItemWriter<Employee> writer() 
{
    return new ConsoleItemWriter<Employee>();
}

Maven 依赖

查看项目依赖项。

pom.xml

<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.howtodoinjava</groupId>
    <artifactId>App</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>App</name>
    <url>http://maven.apache.org</url>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-batch</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
    <repositories>
        <repository>
            <id>repository.spring.release</id>
            <name>Spring GA Repository</name>
            <url>http://repo.spring.io/release</url>
        </repository>
    </repositories>
</project>

示例

在运行该应用程序之前，请查看BatchConfig.java的完整代码。

BatchConfig.java

package com.howtodoinjava.demo.config;
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.support.RunIdIncrementer;
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.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.FileSystemResource;
import com.howtodoinjava.demo.model.Employee;
@Configuration
@EnableBatchProcessing
public class BatchConfig 
{
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Bean
    public Job readCSVFilesJob() {
        return jobBuilderFactory
                .get("readCSVFilesJob")
                .incrementer(new RunIdIncrementer())
                .start(step1())
                .build();
    }
    @Bean
    public Step step1() {
        return stepBuilderFactory.get("step1").<Employee, Employee>chunk(5)
                .reader(reader())
                .writer(writer())
                .build();
    }
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Bean
    public FlatFileItemReader<Employee> reader() 
    {
        //Create reader instance
        FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
        //Set input file location
        reader.setResource(new FileSystemResource("input/inputData.csv"));
        //Set number of lines to skips. Use it if file has header rows.
        reader.setLinesToSkip(1);     
        //Configure how each line will be parsed and mapped to different values
        reader.setLineMapper(new DefaultLineMapper() {
            {
                //3 columns in each row
                setLineTokenizer(new DelimitedLineTokenizer() {
                    {
                        setNames(new String[] { "id", "firstName", "lastName" });
                    }
                });
                //Set values in Employee class
                setFieldSetMapper(new BeanWrapperFieldSetMapper<Employee>() {
                    {
                        setTargetType(Employee.class);
                    }
                });
            }
        });
        return reader;
    }
    @Bean
    public ConsoleItemWriter<Employee> writer() 
    {
        return new ConsoleItemWriter<Employee>();
    }
}

Employee.java

public class Employee {
    String id;
    String firstName;
    String lastName;
    //public setter and getter methods
}

App.java

package com.howtodoinjava.demo;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobParameters;
import org.springframework.batch.core.JobParametersBuilder;
import org.springframework.batch.core.launch.JobLauncher;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
@SpringBootApplication
@EnableScheduling
public class App
{
    @Autowired
    JobLauncher jobLauncher;
    @Autowired
    Job job;
    public static void main(String[] args)
    {
        SpringApplication.run(App.class, args);
    }
    @Scheduled(cron = "0 */1 * * * ?")
    public void perform() throws Exception
    {
        JobParameters params = new JobParametersBuilder()
                .addString("JobID", String.valueOf(System.currentTimeMillis()))
                .toJobParameters();
        jobLauncher.run(job, params);
    }
}

application.properties

#Disable batch job's auto start 
spring.batch.job.enabled=false
spring.main.banner-mode=off

运行应用程序

将应用程序作为 Spring 运行应用程序运行，并观察控制台。 批处理作业将在每分钟开始时开始。 它将读取输入文件，并在控制台中打印读取的值。

Console

2018-07-10 13:28:35 INFO  - Starting App on FFC15B4E9C5AA with PID 12060 (C:\Users\user\app\App\target\classes started by zkpkhua in C:\Users\user\app\App)
2018-07-10 13:28:35 INFO  - No active profile set, falling back to default profiles: default
2018-07-10 13:28:35 INFO  - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@75329a49: startup date [Tue Jul 10 13:28:35 IST 2018]; root of context hierarchy
2018-07-10 13:28:37 INFO  - HikariPool-1 - Starting...
2018-07-10 13:28:38 INFO  - HikariPool-1 - Start completed.
2018-07-10 13:28:38 INFO  - No database type set, using meta data indicating: H2
2018-07-10 13:28:38 INFO  - No TaskExecutor has been set, defaulting to synchronous executor.
2018-07-10 13:28:39 INFO  - Executing SQL script from class path resource [org/springframework/batch/core/schema-h2.sql]
2018-07-10 13:28:39 INFO  - Executed SQL script from class path resource [org/springframework/batch/core/schema-h2.sql] in 74 ms.
2018-07-10 13:28:39 INFO  - Registering beans for JMX exposure on startup
2018-07-10 13:28:39 INFO  - Bean with name 'dataSource' has been autodetected for JMX exposure
2018-07-10 13:28:39 INFO  - Located MBean 'dataSource': registering with JMX server as MBean [com.zaxxer.hikari:name=dataSource,type=HikariDataSource]
2018-07-10 13:28:39 INFO  - No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-07-10 13:28:39 INFO  - Started App in 4.485 seconds (JVM running for 5.33)
2018-07-10 13:29:00 INFO  - Job: [SimpleJob: [name=readCSVFilesJob]] launched with the following parameters: [{JobID=1531209540004}]
2018-07-10 13:29:00 INFO  - Executing step: [step1]
Employee [id=1, firstName=Lokesh, lastName=Gupta]
Employee [id=2, firstName=Amit, lastName=Mishra]
Employee [id=3, firstName=Pankaj, lastName=Kumar]
Employee [id=4, firstName=David, lastName=Miller]
2018-07-10 13:29:00 INFO  - Job: [SimpleJob: [name=readCSVFilesJob]] completed with the following parameters: [{JobID=1531209540004}] and the following status: [COMPLETED]

将我的问题放在评论部分。

学习愉快！