Spring Batch ItemWriter组件

目录

引言

概述

输出平面文件

输出Json文件

输出数据库

输出多终端

转视频版

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引言

接着上篇：Spring Batch ItemProcessor组件-自定义处理器，了解Spring Batch ItemProcessor处理组件后，接下来一起学习一下Spring Batch ItemWriter组件。

概述

有输入那肯定有输出，前面讲了输入ItemReader，接下来就看本篇的输出器：ItemWriter， Spring Batch提供的数据输出组件与数据输入组件是成对，也就是说有啥样子的输入组件，就有啥样子的输出组件。

输出平面文件

当将读入的数据输出到纯文本文件时，可以通过FlatFileItemWriter 输出器实现。

需求：将user.txt中数据读取出来，输出到outUser.txt文件中

1>定义user.txt文件

1#dafei#18
2#xiaofei#16
3#laofei#20
4#zhongfei#19
5#feifei#15

2>定义实体对象

@Getter
@Setter
@ToString
public class User {
    private Long id;
    private String name;
    private int age;
}

3>实现代码

package com.langfeiyes.batch._31_itemwriter_flat;


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.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.FlatFileItemWriter;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.batch.item.file.builder.FlatFileItemWriterBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.PathResource;

import java.util.List;

@SpringBootApplication
@EnableBatchProcessing
public class FlatWriteJob {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public FlatFileItemReader<User> userItemReader(){
        return new FlatFileItemReaderBuilder<User>()
                .name("userItemReader")
                .resource(new ClassPathResource("users.txt"))
                .delimited().delimiter("#")
                .names("id", "name", "age")
                .targetType(User.class)
                .build();
    }

    @Bean
    public FlatFileItemWriter<User> itemWriter(){
        return new FlatFileItemWriterBuilder<User>()
                .name("userItemWriter")
                .resource(new PathResource("c:/outUser.txt"))  //输出的文件
                .formatted()  //数据格式指定
                .format("id: %s,姓名：%s,年龄：%s")  //输出数据格式
                .names("id", "name", "age")  //需要输出属性
                .build();
    }

    @Bean
    public Step step(){
        return stepBuilderFactory.get("step1")
                .<User, User>chunk(1)
                .reader(userItemReader())
                .writer(itemWriter())
                .build();

    }

    @Bean
    public Job job(){
        return jobBuilderFactory.get("flat-writer-job")
                .start(step())
                .build();
    }
    public static void main(String[] args) {
        SpringApplication.run(FlatWriteJob.class, args);
    }
}

解析：

上面代码核心是itemWriter() 方法，设置到itemWrite读取器配置与输出

id: 1,姓名：dafei,年龄：18
id: 2,姓名：xiaofei,年龄：16
id: 3,姓名：laofei,年龄：20
id: 4,姓名：zhongfei,年龄：19
id: 5,姓名：feifei,年龄：15

一些拓展

@Bean
public FlatFileItemWriter<User> itemWriter(){
    return new FlatFileItemWriterBuilder<User>()
        .name("userItemWriter")
        .resource(new PathResource("c:/outUser.txt"))  //输出的文件
        .formatted()  //数据格式指定
        .format("id: %s,姓名：%s,年龄：%s")  //输出数据格式
        .names("id", "name", "age")  //需要输出属性
        .shouldDeleteIfEmpty(true)   //如果读入数据为空，输出时创建文件直接删除
        .shouldDeleteIfExists(true) //如果输出文件已经存在，则删除
        .append(true)  //如果输出文件已经存在， 不删除，直接追加到现有文件中
        .build();
}

输出Json文件

当将读入的数据输出到Json文件时，可以通过JsonFileItemWriter输出器实现。

需求：将user.txt中数据读取出来，输出到outUser.json文件中

沿用上面的user.txt， user对象将数据输出到outUser.json

package com.langfeiyes.batch._32_itemwriter_json;

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.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.FlatFileItemWriter;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.batch.item.file.builder.FlatFileItemWriterBuilder;
import org.springframework.batch.item.json.JacksonJsonObjectMarshaller;
import org.springframework.batch.item.json.JsonFileItemWriter;
import org.springframework.batch.item.json.builder.JsonFileItemWriterBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.PathResource;

@SpringBootApplication
@EnableBatchProcessing
public class JsonWriteJob {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public FlatFileItemReader<User> userItemReader(){
        return new FlatFileItemReaderBuilder<User>()
                .name("userItemReader")
                .resource(new ClassPathResource("users.txt"))
                .delimited().delimiter("#")
                .names("id", "name", "age")
                .targetType(User.class)
                .build();
    }


    @Bean
    public JacksonJsonObjectMarshaller<User> objectMarshaller(){
        JacksonJsonObjectMarshaller marshaller = new JacksonJsonObjectMarshaller();
        return marshaller;
    }

    @Bean
    public JsonFileItemWriter<User> itemWriter(){
        return new JsonFileItemWriterBuilder<User>()
                .name("jsonUserItemWriter")
                .resource(new PathResource("c:/outUser.json"))
                .jsonObjectMarshaller(objectMarshaller())
                .build();
    }


    @Bean
    public Step step(){
        return stepBuilderFactory.get("step1")
                .<User, User>chunk(1)
                .reader(userItemReader())
                .writer(itemWriter())
                .build();

    }

    @Bean
    public Job job(){
        return jobBuilderFactory.get("json-writer-job")
                .start(step())
                .build();
    }
    public static void main(String[] args) {
        SpringApplication.run(JsonWriteJob.class, args);
    }
}

结果：

[
 {"id":1,"name":"dafei","age":18},
 {"id":2,"name":"xiaofei","age":16},
 {"id":3,"name":"laofei","age":20},
 {"id":4,"name":"zhongfei","age":19},
 {"id":5,"name":"feifei","age":15}
]

解析：

1>itemWriter() 实例方法构建JsonFileItemWriter 实例，需要明确指定Json格式装配器

2>Spring Batch默认提供装配器有2个：JacksonJsonObjectMarshaller GsonJsonObjectMarshaller 分别对应Jackson 跟 Gson 2种json格式解析逻辑，本案例用的是Jackson

输出数据库

当将读入的数据需要输出到数据库时，可以通过JdbcBatchItemWriter输出器实现。

需求：将user.txt中数据读取出来，输出到数据库user表中

沿用上面的user.txt， user对象将数据输出到user表中

1>定义操作数据库预编译类

//写入数据库需要操作insert sql， 使用预编译就需要明确指定参数值
public class UserPreStatementSetter implements ItemPreparedStatementSetter<User> {
    @Override
    public void setValues(User item, PreparedStatement ps) throws SQLException {
        ps.setLong(1, item.getId());
        ps.setString(2, item.getName());
        ps.setInt(3, item.getAge());
    }
}

2>完整代码

package com.langfeiyes.batch._33_itemwriter_db;

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.item.database.JdbcBatchItemWriter;
import org.springframework.batch.item.database.builder.JdbcBatchItemWriterBuilder;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.batch.item.json.JacksonJsonObjectMarshaller;
import org.springframework.batch.item.json.JsonFileItemWriter;
import org.springframework.batch.item.json.builder.JsonFileItemWriterBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.PathResource;

import javax.sql.DataSource;

@SpringBootApplication
@EnableBatchProcessing
public class JdbcWriteJob {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Autowired
    private DataSource dataSource;

    @Bean
    public FlatFileItemReader<User> userItemReader(){
        return new FlatFileItemReaderBuilder<User>()
                .name("userItemReader")
                .resource(new ClassPathResource("users.txt"))
                .delimited().delimiter("#")
                .names("id", "name", "age")
                .targetType(User.class)
                .build();
    }
    @Bean
    public UserPreStatementSetter preStatementSetter(){
        return new UserPreStatementSetter();
    }
    @Bean
    public JdbcBatchItemWriter<User>  itemWriter(){
        return new JdbcBatchItemWriterBuilder<User>()
                .dataSource(dataSource)
                .sql("insert into user(id, name, age) values(?,?,?)")
                .itemPreparedStatementSetter(preStatementSetter())
                .build();
    }
    @Bean
    public Step step(){
        return stepBuilderFactory.get("step1")
                .<User, User>chunk(1)
                .reader(userItemReader())
                .writer(itemWriter())
                .build();
    }

    @Bean
    public Job job(){
        return jobBuilderFactory.get("jdbc-writer-job")
                .start(step())
                .build();
    }
    public static void main(String[] args) {
        SpringApplication.run(JdbcWriteJob.class, args);
    }
}

解析：

核心代码在itemWriter() 实例方法中， 需要1>准备构建JdbcBatchItemWriter实例 2>提前准备数据， 3>准备sql语句 4>准备参数绑定器

输出多终端

上面几种输出方法都是一对一，真实开发可能没那么简单了，可能存在一对多，多个终端输出，此时怎么办？答案是使用Spring Batch 提供的CompositeItemWriter 组合输出器。

需求：将user.txt中数据读取出来，输出到outUser.txt/outUser.json/数据库user表中

沿用上面的user.txt， user对象将数据输出到outUser.txt/outUser.json/user表中

package com.langfeiyes.batch._34_itemwriter_composite;

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.item.database.JdbcBatchItemWriter;
import org.springframework.batch.item.database.builder.JdbcBatchItemWriterBuilder;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.FlatFileItemWriter;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.batch.item.file.builder.FlatFileItemWriterBuilder;
import org.springframework.batch.item.json.JacksonJsonObjectMarshaller;
import org.springframework.batch.item.json.JsonFileItemWriter;
import org.springframework.batch.item.json.builder.JsonFileItemWriterBuilder;
import org.springframework.batch.item.support.CompositeItemWriter;
import org.springframework.batch.item.support.builder.CompositeItemWriterBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.PathResource;

import javax.sql.DataSource;
import java.util.Arrays;

@SpringBootApplication
@EnableBatchProcessing
public class CompositeWriteJob {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Autowired
    public DataSource dataSource;

    @Bean
    public FlatFileItemReader<User> userItemReader(){
        return new FlatFileItemReaderBuilder<User>()
                .name("userItemReader")
                .resource(new ClassPathResource("users.txt"))
                .delimited().delimiter("#")
                .names("id", "name", "age")
                .targetType(User.class)
                .build();
    }

    @Bean
    public FlatFileItemWriter<User> flatFileItemWriter(){
        return new FlatFileItemWriterBuilder<User>()
                .name("userItemWriter")
                .resource(new PathResource("c:/outUser.txt"))
                .formatted()  //数据格式指定
                .format("id: %s,姓名：%s,年龄：%s")  //输出数据格式
                .names("id", "name", "age")  //需要输出属性
                .build();
    }

    @Bean
    public JacksonJsonObjectMarshaller<User> objectMarshaller(){
        JacksonJsonObjectMarshaller marshaller = new JacksonJsonObjectMarshaller();
        return marshaller;
    }

    @Bean
    public JsonFileItemWriter<User> jsonFileItemWriter(){
        return new JsonFileItemWriterBuilder<User>()
                .name("jsonUserItemWriter")
                .resource(new PathResource("c:/outUser.json"))
                .jsonObjectMarshaller(objectMarshaller())
                .build();
    }

    @Bean
    public UserPreStatementSetter preStatementSetter(){
        return new UserPreStatementSetter();
    }


    @Bean
    public JdbcBatchItemWriter<User> jdbcBatchItemWriter(){
        return new JdbcBatchItemWriterBuilder<User>()
                .dataSource(dataSource)
                .sql("insert into user(id, name, age) values(?,?,?)")
                .itemPreparedStatementSetter(preStatementSetter())
                .build();
    }

    @Bean
    public CompositeItemWriter<User> compositeItemWriter(){
        return new CompositeItemWriterBuilder<User>()
                .delegates(Arrays.asList(flatFileItemWriter(), jsonFileItemWriter(), jdbcBatchItemWriter()))
                .build();
    }


    @Bean
    public Step step(){
        return stepBuilderFactory.get("step1")
                .<User, User>chunk(1)
                .reader(userItemReader())
                .writer(compositeItemWriter())
                .build();

    }

    @Bean
    public Job job(){
        return jobBuilderFactory.get("composite-writer-job")
                .start(step())
                .build();
    }
    public static void main(String[] args) {
        SpringApplication.run(CompositeWriteJob.class, args);
    }
}

解析：

代码没有啥技术难度，都是将前面的几种方式通过CompositeItemWriter 类整合在一起

@Bean
public CompositeItemWriter<User> compositeItemWriter(){
    return new CompositeItemWriterBuilder<User>()
        .delegates(Arrays.asList(flatFileItemWriter(), jsonFileItemWriter(), jdbcBatchItemWriter()))
        .build();
}

解析：非常简单操作，实现ItemProcessor，定制自己校验标准即可。

到这，本篇就结束了，欲知后事如何，请听下回分解~

转视频版

看文字不过瘾可以切换视频版：Spring Batch高效批处理框架实战