当我们想在Writer之前完成些操作，例如聚合操作的时候可以使用Delegate模式将聚合操作在Delegate Writer操作中完成

public class SnglDenialsRptStatWriterConfig {

    private static final String SNGL_DAILY_CTRL_DATA_INSERT_STATEMENT = DailyCtrlRptDataTempDao.class.getName() + ".insertSelective";

    @Bean("snglDenialsRptStatWriter")
    public ItemWriter<SnglDailyCtrlRptAggregate> snglDenialsRptStatWriter(SqlSessionFactory sqlSessionFactory) {
        MyBatisBatchItemWriter<DailyCtrlRptDataTempPO> myBatisBatchItemWriter = new MyBatisBatchItemWriter<>();
        myBatisBatchItemWriter.setSqlSessionFactory(sqlSessionFactory);
        myBatisBatchItemWriter.setAssertUpdates(false);
        myBatisBatchItemWriter.setStatementId(SNGL_DAILY_CTRL_DATA_INSERT_STATEMENT);
        SnglDenialsRptStatWriter snglDenialsRptStatWriter = new SnglDenialsRptStatWriter();
        // delegate to MyBatisBatchItemWriter
        snglDenialsRptStatWriter.setDelegate(myBatisBatchItemWriter);
        return snglDenialsRptStatWriter;
    }
}

public class SnglDenialsRptStatWriter implements ItemWriter<SnglDailyCtrlRptAggregate> {

    private ItemWriter<DailyCtrlRptDataTempPO> delegate;

    public void setDelegate(ItemWriter<DailyCtrlRptDataTempPO> delegate) {
        this.delegate = delegate;
    }

    @Autowired
    private SnglDailyCtrlRptConverter snglDailyCtrlRptConverter;

    @Override
    public void write(List<? extends SnglDailyCtrlRptAggregate> list) throws Exception {
        if (!list.isEmpty()) {
            // map use for merge denials records by partition
            Map<String, SnglDailyCtrlRptTempDO> denialsRecordsMergeMap = Maps.newHashMap();
            list.stream().filter(Objects::nonNull).forEach(each -> {
                log.info("====> process each record {}", each);
                List<SnglDailyCtrlRptTempDO> denialsRecords = each.getDenialsRecords();
                //merge denials records by partition
                each.mergeByPartition(denialsRecordsMergeMap, denialsRecords);
            });
            List<SnglDailyCtrlRptTempDO> listDO = Lists.newArrayList(denialsRecordsMergeMap.values());
            // get output list PO for MyBatisBatchItemWriter
            List<DailyCtrlRptDataTempPO> outPutList = snglDailyCtrlRptConverter.map(listDO,
                    DailyCtrlRptDataTempPO.class);
            // delegate to MyBatisBatchItemWriter
            delegate.write(outPutList);
        }
    }
}

适配器代理模式样例

private static class GatewayFilterAdapter implements GatewayFilter {

        private final GlobalFilter delegate;

        GatewayFilterAdapter(GlobalFilter delegate) {
            this.delegate = delegate;
        }

        @Override
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
            return this.delegate.filter(exchange, chain);
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("GatewayFilterAdapter{");
            sb.append("delegate=").append(delegate);
            sb.append('}');
            return sb.toString();
        }

    }

springbatch学习项目