Question

我在数据库中有一个包含这些列的表：

   id serial NOT NULL, 
   name character varying(255) NOT NULL, 
   url character varying(255)

实体：

    @Entity
    @Table(name = "Topmenu")
    @XmlRootElement
    @NamedQueries({
        @NamedQuery(name = "Topmenu.findAll", query = "SELECT t FROM Topmenu t"),
        @NamedQuery(name = "Topmenu.findById", query = "SELECT t FROM Topmenu t WHERE t.id = :id")})
    public class Topmenu implements Serializable {

        private static final long serialVersionUID = 1L;
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Basic(optional = false)
        @Column(name = "id")
        private Integer id;
        @Basic(optional = false)
        @Column(name = "name")
        private String name;
        @Column(name = "url")
        private String url;

        public Topmenu() {
        }

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

        public Topmenu(Integer id, String name) {
            this.id = id;
            this.name = name;
        }

        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getUrl() {
            return url;
        }

        public void setUrl(String url) {
            this.url = url;
        }

        @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 Topmenu)) {
                return false;
            }
            Topmenu other = (Topmenu) object;
            return !((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id)));
        }

        @Override
        public String toString() {
            return "erates.entity.Topmenu[ id=" + id + " ]";
        }
}

Netbeans为我生成了JPA实体。我在数据库中有5条记录。当我em.createNamedQuery("Topmenu.findAll").getResultList();时，我得到一个包含5个条目的List<Topmenu>，但是当我执行以下操作时，不会返回任何内容：

for(Topmenu t : em.createNamedQuery("Topmenu.findAll").getResultList()){
    logger.warn(t.getName());
}

命名查询：

@NamedQuery(name = "Topmenu.findAll", query = "Topmenu t FROM Topmenu t")

输出：

2015-06-01 11:23:27,024 WARN erates.beans.TopmenuBean (TopmenuBean.java:33) -
2015-06-01 11:23:27,034 WARN erates.beans.TopmenuBean (TopmenuBean.java:33) -
2015-06-01 11:23:27,045 WARN erates.beans.TopmenuBean (TopmenuBean.java:33) -
2015-06-01 11:23:27,055 WARN erates.beans.TopmenuBean (TopmenuBean.java:33) -
2015-06-01 11:23:27,066 WARN erates.beans.TopmenuBean (TopmenuBean.java:33) -

Answer 1

根据我的经验，当你没有使用TypedQueries并且需要它们时会出现一些问题。

使用

尝试使用代码

for(Topmenu t : em.createNamedQuery("Topmenu.findAll", Topmenu.class).getResultList()){
    logger.warn(t.getName());
}

使用additional参数，createNamedQuery将返回TypedQuery而不是Query。

让我知道它是否有帮助：）

Answer 2

这与实体或EntityManager无关，而是与EclipseLink编织的事实有关。我忘记了一个细节，即获得Entities的EJB是一个远程EJB。因此序列化对象时会出现错误，导致TopmenuBean获取对象，但无法对其进行反序列化。

问题现在解决了

NamedQuery resultList返回对象，但所有值都为null

2 个答案: