Question

更新我似乎如果我添加时间戳它会导致问题，但我不知道为什么。我尝试了一些建议，但遗憾的是它无法正常工作

@Basic(optional = true)
@NotNull
@Column(name="created", columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
@Temporal(TemporalType.TIMESTAMP)
private Date created;

更新＃2

这是最糟糕的结果：问题已得到解决，但我不知道为什么！我将实体类更改为：

@Basic(optional = false)
@Column(name="created", insertable = false, updatable = false)
@Temporal(TemporalType.TIMESTAMP)
private Date created;

它仍然无效。我重启了玻璃鱼，它仍然无法正常工作。我去参加了一个会议，重新开始了， IT WORKED 我很生气，因为我什么也没学到，并且花了几个小时就应该花30秒。

我在Netbeans上以调试模式编辑项目，所以我希望我的所有更改都可以在文件保存时重新部署。如果不是这种情况，也许你可以解释一下。

我还尝试设置 org.hibernate.ejb.HibernatePersistence ，但我现在放弃了......）

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TL; DR

我已经挣扎了几个小时并阅读了我在SOF上找到的所有帖子。

为了让这个工作变得有效，我最终摧毁了我的桌子，虽然我已经定义了一个自动增量的主要ID我得到了

对象：entities.Json [id = null]不是已知的实体类型。

错误，如果我设置了值，我得到了

在回调事件上执行自动Bean验证时违反了

Bean验证约束：'prePersist'。有关详细信息，请参阅嵌入式ConstraintViolations。

错误。

MySQL表

CREATE TABLE `evaluationdb`.`json` ( `id` INT NOT NULL AUTO_INCREMENT , 
`ref_id` INT NOT NULL , 
`json` VARCHAR(4096) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL , 
`created` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ,
PRIMARY KEY (`id`)) 
ENGINE = InnoDB CHARACTER SET utf8 COLLATE utf8_general_ci;

Entitiy

package entities;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;

@Entity
@Table(name = "json")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Json.findAll", query = "SELECT j FROM Json j")
    , @NamedQuery(name = "Json.findById", query = "SELECT j FROM Json j WHERE j.id = :id")
    , @NamedQuery(name = "Json.findByRefid", query = "SELECT j FROM Json j WHERE j.refid = :refid")
    , @NamedQuery(name = "Json.findByJson", query = "SELECT j FROM Json j WHERE j.json = :json")})
public class Json 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)
    @NotNull
    @Column(name = "refid")
    private int refid;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 4096)
    @Column(name = "json")
    private String json;

    public Json() {
    }

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

    public Json(Integer id, int refid, String json) {
        this.id = id;
        this.refid = refid;
        this.json = json;
    }

    public Integer getId() {
        return id;
    }

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

    public int getRefid() {
        return refid;
    }

    public void setRefid(int refid) {
        this.refid = refid;
    }

    public String getJson() {
        return json;
    }

    public void setJson(String json) {
        this.json = json;
    }

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

    @Override
    public String toString() {
        return "entities.Json[ id=" + id + " ]";
    }

}

persistance.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="com.mycompany_responseableES_war_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">
        <!--<jta-data-source>java:app/responseablees_working</jta-data-source>-->
        <class>entities.Openanswer</class>
        <class>com.company.responseablees.entities.ResponseHasOpenanswer</class>
        <class>entities.Json</class>
        <exclude-unlisted-classes>false</exclude-unlisted-classes>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/evaluationdb"/>
            <property name="javax.persistence.jdbc.user" value="responseablees"/>
            <property name="javax.persistence.jdbc.password" value="responseablees"/>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <!--         <property name="eclipselink.logging.level" value="FINE"/>
            <property name="eclipselink.ddl-generation" value="create-tables"/>-->
        </properties>
    </persistence-unit>
</persistence>

代码

EntityManagerFactory emfactory = Persistence.createEntityManagerFactory("com.mycompany_responseableES_war_1.0-SNAPSHOTPU");
EntityManager em = emfactory.createEntityManager( );
em.getTransaction().begin();
Json json = new Json();

json.setId(1);
json.setRefid(1);
json.setJson("test");

em.persist(json);
em.getTransaction().commit();

是否有人发现我列出的代码存在问题？

Answer 1

有机会＆＃39; id＆＃39;字段为NULL，因为它是一个整数。如果使用int而不是Integer，则问题将得到解决。只有当列可以为空时，才应使用Integer。标准做法是使用原语，除非您处理泛型

阅读java中的autoboxing and unboxing以获得更多理解。

JPA保持不断“对象：entities.Json [id = null]不是已知的实体类型。”

1 个答案: