我想將 XML 響應(yīng)拆分為多個(gè)頁(yè)面，因?yàn)槲矣刑嗟?XML 項(xiàng)要發(fā)回。我試過(guò)這個(gè)：XML 請(qǐng)求：<?xml version="1.0" encoding="UTF-8"?><reconcile> <start_date>2018-04-08T11:02:44</start_date> <end_date>2019-10-08T11:02:44</end_date> <page>1</page></reconcile>JAXB：@XmlRootElement(name = "reconcile")@XmlAccessorType(XmlAccessType.FIELD)public class Reconcile { @XmlElement(name = "start_date") @XmlJavaTypeAdapter(LocalDateTimeXmlAdapter.class) private LocalDateTime start_date; @XmlElement(name = "end_date") @XmlJavaTypeAdapter(LocalDateTimeXmlAdapter.class) private LocalDateTime end_date; @XmlElement(name = "page") private String page; ...../// getters and setters}SQL查詢：public List<PaymentTransactions> transactionsByDate(LocalDateTime start_date, LocalDateTime end_date, Merchants merchant, Terminals terminal) throws Exception { String hql = "select e from " + PaymentTransactions.class.getName() + " e where e.created_at >= ? and e.created_at <= ?"; Query query = entityManager.createQuery(hql).setParameter(0, start_date).setParameter(1, end_date); List<PaymentTransactions> paymentTransactions = (List<PaymentTransactions>) query.getResultList(); return paymentTransactions;}我想以某種方式<payment_response>....</payment_response>分成頁(yè)面以減少內(nèi)存開(kāi)銷。例如，當(dāng)我發(fā)送 1 時(shí)，我想返回前 10 個(gè)。我該如何實(shí)施？
1 回答
瀟湘沐
TA貢獻(xiàn)1816條經(jīng)驗(yàn) 獲得超6個(gè)贊
你怎么看這樣的事情？對(duì)不起，這是未經(jīng)測(cè)試的代碼，但這樣的事情應(yīng)該可以工作。
我創(chuàng)建了一個(gè)新的 PageInfo 類來(lái)存儲(chǔ)分頁(yè)信息。添加了一個(gè)查詢以獲取總行數(shù)并設(shè)置我的 page_info。然后限制查詢結(jié)果的數(shù)量。最后將值設(shè)置為 ReconcilePaymentResponse。
Class PageInfo {
int current_page;
int page_count;
int per_page;
int total_page;
//constructor
public PageInfo(int current_page, int page_count, int per_page) {
//assign them
}
//getters
//setters
}
SQL查詢：
public List<PaymentTransactions> transactionsByDate(LocalDateTime start_date, LocalDateTime end_date, Merchants merchant, Terminals terminal,
PageInfo pageInfo) throws Exception {
//figure out number of total rows
String count_hql = "select count(*) from " + PaymentTransactions.class.getName() + " e where e.created_at >= ? and e.created_at <= ?";
Query count_query = entityManager.createQuery(count_hql);
int count = countQuery.uniqueResult();
//figure out total pages
int total_page = (int)Math.ceil(count/(double)pageInfo.getPerPage());
pageInfo.setTotal_Page(total_page);
String hql = "select e from " + PaymentTransactions.class.getName() + " e where e.created_at >= ? and e.created_at <= ?";
Query query = entityManager.createQuery(hql)
//set starting point
.setFirstResult((pageInfo.getCurrentPage()-1) * pageInfo.getPerPage)
//set max rows to return
.setMaxResults(pageInfo.getPerPage)
.setParameter(0, start_date).setParameter(1, end_date);
List<PaymentTransactions> paymentTransactions = (List<PaymentTransactions>) query.getResultList();
return paymentTransactions;
}
返回 XML：
//initialize PageInfo with desired values
PageInfo page_info = new PageInfo(1,10,4);
List<PaymentTransactions> paymentTransactions = transactionsService
.transactionsByDate(reconcile.getStart_date(), reconcile.getEnd_date(), merchant, terminal, page_info); // pass in page_info
ReconcilePaymentResponses pr = new ReconcilePaymentResponses();
pr.setPage(page_info.getCurrentPage());
pr.setPages_count(page_info.getPageCount());
pr.setPer_page(page_info.getPerPage());
pr.setTotal_count(String.valueOf(paymentTransactions.size()));
for (int e = 0; e < paymentTransactions.size(); e++) {
PaymentTransactions pt = paymentTransactions.get(e);
ReconcilePaymentResponse obj = new ReconcilePaymentResponse();
obj.setTransaction_type(pt.getType());
pr.getPaymentResponse().add(obj);
}
return pr;
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