java - for 循环内的 .contains()

Question

我使用 for 循环在验证时迭代持久表单对象，然后与非持久表单对象进行比较。我在循环中使用 .contains，但是第一个循环返回 true，而每个其他循环返回 false，即使 pr 对象不包含 prPersist 对象。有人可以告诉我我做错了什么，或者是否有更好的方法来处理这个问题？谢谢

hibernate 实体

PurchaseRequest 对象

    @OneToMany(mappedBy = "purchaseRequest", cascade=CascadeType.ALL, orphanRemoval=true)

public List<LineItem> getLineItems() {
    if(lineItems == null ){
        lineItems = new ArrayList<LineItem>();
    }
    return lineItems;
}

public void setLineItems(List<LineItem> lineItems) {
    this.lineItems = lineItems;
}

LineItem 对象

@ManyToOne
@JoinColumn(name = "pr_id", nullable = false)
private PurchaseRequest purchaseRequest;

public PurchaseRequest getPurchaseRequest() {
    return purchaseRequest;
}

public void setPurchaseRequest(PurchaseRequest purchaseRequest) {
    this.purchaseRequest = purchaseRequest;
}

页面类

    private List<LineItem> lineItems;

    private PurchaseRequest pr;

    @Persist
    private PurchaseRequest prPersist;

    System.out.println("prPersist size " + prPersist != null ? prPersist.getLineItems().size() : "");
    System.out.println("pr size outer loop " + pr.getLineItems().size());
    if(prPersist != null) {
        for(LineItem _lineItem : prPersist.getLineItems()) {
            System.out.println("pr lineItem object value " + _lineItem.getQuantity());
            System.out.println("pr lineItem size inner loop " + pr.getLineItems().size());
            System.out.println("pr lineItem contains prPersist lineItem " + pr.getLineItems().contains(_lineItem));
            if(!pr.getLineItems().contains(_lineItem)) {
                _lineItem.setPurchaseRequest(pr);
                pr.getLineItems().add(_lineItem);
                System.out.println("new line item added");
            }
        }
        prPersist = null;
    }

打印结果

prPersist size 2
pr size outer loop 0
pr lineItem object value 4
pr lineItem size inner loop 0
pr lineItem contains prPersist lineItem false
new line item added
pr lineItem object value 5
pr lineItem size inner loop 1
pr lineItem contains prPersist lineItem true

设置prPersist

void onValidate() {
    prPersist = null;

    if (form.getHasErrors()) {
        prPersist = pr;            
    }
}

Answer 1

鉴于 prPersist 和 'pr' 是不同的实例，我猜测每个包含的 LineItem 可能是不同的实例？

如果是这样，我猜您在 LineItem 上实现 equals 方法时遇到了问题。