springbatch-ItemReader使用

从数据库中读取数据

@Configuration
public class ItemReaderDbDemo {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private DataSource dataSource;

    @Bean
    public Job itemReaderDbJob(){
        return jobBuilderFactory
                .get("itemReaderDbJob")
                .start(itemReaderDbStep())
                .build();
    }

    @Bean
    public Step itemReaderDbStep(){
        return stepBuilderFactory
                .get("itemReaderDbStep")
                .<User,User>chunk(2)
                .reader(dbJdbcReader())
                .writer(new ItemWriter<User>() {
                    @Override
                    public void write(List<? extends User> list) throws Exception {
                        System.out.println(list);
                    }
                })
                .build();
    }
    @Bean
    @StepScope
    public JdbcPagingItemReader<User> dbJdbcReader(){
        JdbcPagingItemReader<User> reader = new JdbcPagingItemReader<>();
        reader.setDataSource(dataSource);//设置数据源
        reader.setFetchSize(2);//一次去多少记录
        //把读取到的记录转换成user对象
        reader.setRowMapper(new RowMapper<User>() {
            @Override
            public User mapRow(ResultSet rs, int rowNum) throws SQLException {
                User user = new User();
                user.setId(rs.getInt(1));
                user.setName(rs.getString(2));
                user.setPass(rs.getString(3));
                return user;
            }
        });
        //指定sql语句
        MySqlPagingQueryProvider provider = new MySqlPagingQueryProvider();
        provider.setSelectClause("id,name,pass");//查哪些字段
        provider.setFromClause("from t_user");//从哪个表查
        //排序
        Map<String, Order> sort = new HashMap<>(1);
        sort.put("id",Order.DESCENDING);//排序字段，升序还是降序
        provider.setSortKeys(sort);

        reader.setQueryProvider(provider);
        return reader;
    }
}

从文件中读取数据

@Configuration
public class FileItemReaderDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public Job fileItemReaderDemoJob(){
        return jobBuilderFactory
                .get("fileItemReaderDemoJob")
                .start(fileItemReaderDemoStep())
                .build();
    }
    @Bean
    public Step fileItemReaderDemoStep(){
        return stepBuilderFactory
                .get("fileItemReaderDemoStep")
                .<User,User>chunk(2)
                .reader(flatFileItemReader())
                .writer(System.out::println)
                .build();
    }

    @Bean
    @StepScope
    public FlatFileItemReader<User> flatFileItemReader(){
        FlatFileItemReader<User> reader = new FlatFileItemReader<>();
        reader.setResource(new ClassPathResource("users.txt"));//文件地址
        reader.setLinesToSkip(1);//跳过第一行
        //解析数据
        DelimitedLineTokenizer tokenizer = new DelimitedLineTokenizer();
        tokenizer.setNames(new String[]{"id","name","pass"});//指明表头字段
        //把解析的一行数据映射为对象
        DefaultLineMapper<User> mapper = new DefaultLineMapper<>();
        mapper.setLineTokenizer(tokenizer);
        mapper.setFieldSetMapper(new FieldSetMapper<User>() {
            @Override
            public User mapFieldSet(FieldSet fieldSet) throws BindException {
                User user = new User();
                user.setId(fieldSet.readInt("id"));
                user.setName(fieldSet.readString("name"));
                user.setPass(fieldSet.readString("pass"));
                return user;
            }
        });
        mapper.afterPropertiesSet();
        reader.setLineMapper(mapper);
        return reader;
    }
}

从xml中读取数据

@Configuration
public class XmlItemReaderDemo {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public Job xmlItemReaderDemoJob(){
        return jobBuilderFactory
                .get("xmlItemReaderDemoJob")
                .start(xmlItemReaderDemoStep())
                .build();
    }

    @Bean
    public Step xmlItemReaderDemoStep(){
        return stepBuilderFactory
                .get("xmlItemReaderDemoStep")
                .<User,User>chunk(2)
                .reader(xmlFileReader())
                .writer(System.out::println)
                .build();
    }

    @Bean
    @StepScope
    public StaxEventItemReader<User> xmlFileReader(){
        StaxEventItemReader<User> reader = new StaxEventItemReader<>();
        reader.setResource(new ClassPathResource("users.xml"));//从哪个文件读
        //设置需要处理的根标签
        reader.setFragmentRootElementName("user");
        //把xml转成对象
        XStreamMarshaller marshaller = new XStreamMarshaller();
        //设置类型转换
        Map<String,Class> map = new HashMap<>();
        map.put("user",User.class);//标签名，类型
        marshaller.setAliases(map);

        reader.setUnmarshaller(marshaller);
        return reader;
    }
}

需要引入依赖：

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-oxm</artifactId>
    <version>5.3.10</version>
</dependency>

<dependency>
    <groupId>com.thoughtworks.xstream</groupId>
    <artifactId>xstream</artifactId>
    <version>1.4.7</version>
</dependency>

读取多个文件的数据

@Configuration
public class MultiFileItemReaderDemo {
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Value("classpath:/user*.txt")
    private Resource[] fileResources;

    @Bean
    public Job multiFileItemReaderDemoJob(){
        return jobBuilderFactory
                .get("multiFileItemReaderDemoJob")
                .start(multiFileItemReaderDemoStep())
                .build();

    }
    @Bean
    public Step multiFileItemReaderDemoStep(){
        return stepBuilderFactory
                .get("multiFileItemReaderDemoStep")
                .<User,User>chunk(2)
                .reader(multiFileReader())
                .writer(System.out::println)
                .build();
    }

    @Bean
    @StepScope
    public MultiResourceItemReader<User> multiFileReader(){
        MultiResourceItemReader<User> reader = new MultiResourceItemReader<>();
        reader.setDelegate(flatFileItemReader());
        reader.setResources(fileResources);//设置文件源
        return reader;
    }
    //从一个文件中读取
    @Bean
    @StepScope
    public FlatFileItemReader<User> flatFileItemReader(){
        FlatFileItemReader<User> reader = new FlatFileItemReader<>();
        //解析数据
        DelimitedLineTokenizer tokenizer = new DelimitedLineTokenizer();
        tokenizer.setNames(new String[]{"id","name","pass"});//指明表头字段
        //把解析的一行数据映射为对象
        DefaultLineMapper<User> mapper = new DefaultLineMapper<>();
        mapper.setLineTokenizer(tokenizer);
        mapper.setFieldSetMapper(new FieldSetMapper<User>() {
            @Override
            public User mapFieldSet(FieldSet fieldSet) throws BindException {
                User user = new User();
                user.setId(fieldSet.readInt("id"));
                user.setName(fieldSet.readString("name"));
                user.setPass(fieldSet.readString("pass"));
                return user;
            }
        });
        mapper.afterPropertiesSet();
        reader.setLineMapper(mapper);
        return reader;
    }
}