为什么JPA repeat persist方法不抛出异常？

Question

Product product = new Product();
product.setName( "foo" );
product.setPrice(BigDecimal.valueOf( 4.5 ) );
pm.create( product ); // pm delegates calls to an entity manager object using persist method and tx is immediately commited after the call

List<Product> products = pm.findAllProducts();
products.stream().forEach( System.out::println ); // New product is listed too.

pm.create( product ); // Causes no exception! But, as per API, it should.

products = pm.findAllProducts(); // Fetch successful
products.stream().forEach( System.out::println ); // No difference from first print.

null

1. 为简洁起见，排除了getter和setter（用于所有字段）以及toString（）。
2. 我尽了最大的努力按照指导原则格式化代码，但它没有发生，请耐心等待。

@Entity@Table（name=“Products”）@XmlRootElement@NamedQueries（{@NamedQuery（name=“Product.FindAll”,query=“从产品p中选择p”），@namedquery（name=“Product.FindById”,query=“从产品p中选择p,其中p.id=：id”）,@namedquery（name=“Product.FindByName”,query=“从产品p中选择p,其中p.name like：name”）,@namedquery（name=“Product.FindByPrice”,query=“从产品p中选择p,其中p.price=：price”）,@namedquery（name=“Product.FindByBestBefore”,query=“从产品p中选择p,其中p.bestBefore=：

公共类产品实现Serializable{

private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@NotNull
@SequenceGenerator( name="pidGen", sequenceName="PID_SEQ", allocationSize=1 )
@GeneratedValue( strategy=SEQUENCE, generator="pidGen" )
private Integer id;
@Basic(optional = false)
@NotNull
@Size(min = 3, max = 40, message="{prod.name}")
private String name;
// @Max(value=?)  @Min(value=?)//if you know range of your decimal fields consider using these annotations to enforce field validation
@Basic(optional = false)
@NotNull
@Max( value=1000, message="{prod.price.max}")
@Min( value=1, message="{prod.price.min}")
private BigDecimal price;
@Column(name = "BEST_BEFORE")
@Temporal(TemporalType.DATE)
//private Date bestBefore;
private LocalDate bestBefore;
@Version
private Integer version;

public Product() {
}

public Product(Integer id) {
    this.id = id;
}

public Product(Integer id, String name, BigDecimal price) {
    this.id = id;
    this.name = name;
    this.price = price;
}



@Override
public int hashCode() {
    int hash = 0;
    hash += (id != null ? id.hashCode() : 0);
    return hash;
}

@Override
public boolean equals(Object object) {
    // TODO: Warning - this method won't work in the case the id fields are not set
    if (!(object instanceof Product)) {
        return false;
    }
    Product other = (Product) object;
    if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
        return false;
    }
    return true;
}


 }

Answer 1

根据JPA规范：

>

如果X是一个新实体，则它成为托管实体。实体X将在事务提交时或之前或作为刷新操作的结果被输入数据库。

如果X是一个预先存在的托管实体，它将被persist操作忽略（...）