@QueryHints(value=@QueryHint(name=HINT_FETCH_SIZE,value=""+Integer.MIN_VALUE))
@Query(value="selecttfromTodot")
StreamstreamAll();此外还需要在Stream处理数据的方法之上添加
@Transactional(readOnly = true)
保证事务是只读的。同时需要注入javax.persistence.EntityManager，通过detach从内存中移除已经使用后的对象。
@RequestMapping(value="/todos.csv",method=RequestMethod.GET)
@Transactional(readOnly=true)
publicvoidexportTodosCSV(HttpServletResponseresponse){
response.addHeader("Content-Type","application/csv");
response.addHeader("Content-Disposition","attachment;filename=todos.csv");
response.setCharacterEncoding("UTF-8");
try(StreamtodoStream=todoRepository.streamAll()){
PrintWriterout=response.getWriter();
todoStream.forEach(rethrowConsumer(todo->{
Stringline=todoToCSV(todo);
out.write(line);
out.write("");
entityManager.detach(todo);
}));
out.flush();
} catch(IOExceptione){
log.info("Exceptionoccurred"+e.getMessage(),e);
thrownewRuntimeException("Exceptionoccurredwhileexportingresults",e);
}
}