我在Hibernate和oneToManyMap方面遇到了一些问题。
下面是我的函数：

Location location = new Location();
        location.setDateTime(new Date());
        location.setLatitude(lat);
        location.setLongitude(lon);

        location = this.locationDao.save(location);

        merchant = new Merchant();
        merchant.setAddress(address);
        merchant.setCity(city);
        merchant.setCountry(country);
        merchant.setLocation(location);
        merchant.setName(name);
        merchant.setOrganization(organization);
        merchant.setPublicId(publicId);
        merchant.setZipCode(zipCode);
        merchant.setApplication(this.applicationDAO.findByPublicId(applicationPublicId));

        merchant = this.merchantDao.save(merchant);

        return merchant;

下面是我的两个实体：

• • 地点**

import java.io.Serializable;
import java.util.Date;
import java.util.List;
import javax.persistence.*;
import javax.validation.constraints.NotNull;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;

@Entity
@Table(name = "location")
@XmlRootElement
public class Location implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id", nullable = false)
    private Long id;

    @Basic(optional = false)
    @NotNull
    @Column(name = "latitude", nullable = false)
    private double latitude;

    @Basic(optional = false)
    @NotNull
    @Column(name = "longitude", nullable = false)
    private double longitude;

    @Basic(optional = false)
    @NotNull
    @Column(name = "date_time", nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    private Date dateTime;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "location")
    private List<Merchant> retailerList;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "location")
    private List<MobileUser> userList;

    public Location() {
    }

    public Location(Long id) {
        this.id = id;
    }

    public Location(Long id, double latitude, double longitude, Date dateTime) {
        this.id = id;
        this.latitude = latitude;
        this.longitude = longitude;
        this.dateTime = dateTime;
    }

    public Long getId() {
        return id;
    }
    //getters and setters

    @XmlTransient
    public List<Merchant> getRetailerList() {
        return retailerList;
    }

    public void setRetailerList(List<Merchant> retailerList) {
        this.retailerList = retailerList;
    }

    @XmlTransient
    public List<MobileUser> getUserList() {
        return userList;
    }

    public void setUserList(List<MobileUser> userList) {
        this.userList = userList;
    }

    @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 Location)) {
            return false;
        }
        Location other = (Location) 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 "com.fgsecure.geoloc.entities.Location[ id=" + id + " ]";
    }

• • 商人**

import java.io.Serializable;
import javax.persistence.*;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;
import org.codehaus.jackson.annotate.JsonAutoDetect;
import org.codehaus.jackson.annotate.JsonIgnore;

@JsonAutoDetect
@Entity
@Table(name = "retailer")
@XmlRootElement

public class Merchant implements Serializable {

    private static final long serialVersionUID = 1L;
    @JsonIgnore
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id", nullable = false)
    private Long id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "public_id", nullable = false, length = 50)
    private String publicId;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "name", nullable = false, length = 50)
    private String name;
    @Size(max = 50)
    @Column(name = "organization", length = 50)
    private String organization;
    @Size(max = 128)
    @Column(name = "address", length = 128)
    private String address;
    @Size(max = 10)
    @Column(name = "zip_code", length = 10)
    private String zipCode;
    @Size(max = 50)
    @Column(name = "city", length = 50)
    private String city;
    @Size(max = 50)
    @Column(name = "country", length = 50)
    private String country;
    @JoinColumn(name = "location_id", referencedColumnName = "id", nullable = false)
    @ManyToOne(optional = false)
    private Location location;
    @JoinColumn(name = "application_id", referencedColumnName = "id", nullable = false)
    @ManyToOne(optional = false)
    private Application application;

    public Merchant() {
    }

    public Merchant(Long id) {
        this.id = id;
    }

    public Merchant(Long id, String publicId, String name) {
        this.id = id;
        this.publicId = publicId;
        this.name = name;
    }

   //getters and setters

    @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 Merchant)) {
            return false;
        }
        Merchant other = (Merchant) 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 "com.fgsecure.geoloc.entities.Retailer[ id=" + id + " ]";
    }
}

每次调用函数时，我得到：

org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save():

对于此行：

location = this.locationDao.save(location);

我不明白为什么。因为在这种情况下，没有必要手动分配的ID的位置，因为它是自动生成的。我一定是做错了什么，但经过3天的寻找，我没有找到。
我使用的是PostGreSQL，ID是自动生成的ID，序列如下：

nextval('location_id_seq'::regclass)`

• • 编辑求解：**

好的谢谢你的回答.
如果将来可以帮助其他人，只需修改id的参数：

@Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id",unique=true, nullable = false)