Spring Batch：读取数据库并写入多记录平面文件

Question

Hi I am doing POC/base for design on reading database and writing into flat files. I am struggling on couple of issues here but first I will tell you the output format of flat file

Please let me know how do design the input writer where I need to read the transactions from different tables, process records , figure out the summary fields and then how should I design the Item Writer which has such a complex design. Please advice. I am successfully able to read from single table and write to file but the above task looks complex.

Answer 1

Extend the FlatFileItemWriter to only open a file once and append to it instead of overwriting it. Then pass that same filewriter into multiple readers in the order you would like them to appear. (Make sure that each object read by the readers are extensible by something that the writer understands! Maybe interface BatchWriteable would be a good name.)

Some back-of-the-envelope pseudocode:

Before everything starts:

• Open file.
• Write file headers.
• Start Batch step

implement as many times as necessary

• Read Batch section
• Process Batch section
• A Write Batch section

when done:

• Write file footer
• Close file