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Spring Batch ItemWriter元件

目錄

引言

概述

輸出平面檔案

輸出Json檔案

輸出資料庫

輸出多終端

轉視訊版

引言

接着上篇：Spring Batch ItemProcessor元件-自定義處理器，了解Spring Batch ItemProcessor處理元件後，接下來一起學習一下Spring Batch ItemWriter元件。

概述

有輸入那肯定有輸出，前面講了輸入ItemReader，接下來就看本篇的輸出器：ItemWriter， Spring Batch提供的資料輸出元件與資料輸入元件是成對，也就是說有啥樣子的輸入元件，就有啥樣子的輸出元件。

輸出平面檔案

當将讀入的資料輸出到純文字檔案時，可以通過FlatFileItemWriter 輸出器實作。

需求：将user.txt中資料讀取出來，輸出到outUser.txt檔案中

1>定義user.txt檔案

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

2>定義實體對象

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

3>實作代碼

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"))  //輸出的檔案
                .formatted()  //資料格式指定
                .format("id: %s,姓名：%s,年齡：%s")  //輸出資料格式
                .names("id", "name", "age")  //需要輸出屬性
                .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：

上面代碼核心是itemWriter() 方法，設定到itemWrite讀取器配置與輸出

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

一些拓展

@Bean
public FlatFileItemWriter<User> itemWriter(){
    return new FlatFileItemWriterBuilder<User>()
        .name("userItemWriter")
        .resource(new PathResource("c:/outUser.txt"))  //輸出的檔案
        .formatted()  //資料格式指定
        .format("id: %s,姓名：%s,年齡：%s")  //輸出資料格式
        .names("id", "name", "age")  //需要輸出屬性
        .shouldDeleteIfEmpty(true)   //如果讀入資料為空，輸出時建立檔案直接删除
        .shouldDeleteIfExists(true) //如果輸出檔案已經存在，則删除
        .append(true)  //如果輸出檔案已經存在， 不删除，直接追加到現有檔案中
        .build();
}

輸出Json檔案

當将讀入的資料輸出到Json檔案時，可以通過JsonFileItemWriter輸出器實作。

需求：将user.txt中資料讀取出來，輸出到outUser.json檔案中

沿用上面的user.txt， user對象将資料輸出到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);
    }
}

結果：

[
 {"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() 執行個體方法建構JsonFileItemWriter 執行個體，需要明确指定Json格式裝配器

2>Spring Batch預設提供裝配器有2個：JacksonJsonObjectMarshaller GsonJsonObjectMarshaller 分别對應Jackson 跟 Gson 2種json格式解析邏輯，本案例用的是Jackson

輸出資料庫

當将讀入的資料需要輸出到資料庫時，可以通過JdbcBatchItemWriter輸出器實作。

需求：将user.txt中資料讀取出來，輸出到資料庫user表中

沿用上面的user.txt， user對象将資料輸出到user表中

1>定義操作資料庫預編譯類

//寫入資料庫需要操作insert sql， 使用預編譯就需要明确指定參數值
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>完整代碼

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：

核心代碼在itemWriter() 執行個體方法中， 需要1>準備建構JdbcBatchItemWriter執行個體 2>提前準備資料， 3>準備sql語句 4>準備參數綁定器

輸出多終端

上面幾種輸出方法都是一對一，真實開發可能沒那麼簡單了，可能存在一對多，多個終端輸出，此時怎麼辦？答案是使用Spring Batch 提供的CompositeItemWriter 組合輸出器。

需求：将user.txt中資料讀取出來，輸出到outUser.txt/outUser.json/資料庫user表中

沿用上面的user.txt， user對象将資料輸出到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()  //資料格式指定
                .format("id: %s,姓名：%s,年齡：%s")  //輸出資料格式
                .names("id", "name", "age")  //需要輸出屬性
                .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：

代碼沒有啥技術難度，都是将前面的幾種方式通過CompositeItemWriter 類整合在一起

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

解析：非常簡單操作，實作ItemProcessor，定制自己校驗标準即可。

到這，本篇就結束了，欲知後事如何，請聽下回分解~

轉視訊版

看文字不過瘾可以切換視訊版：Spring Batch高效批處理架構實戰

Spring Batch 極簡入門 spring batch java itemwriter
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