如何增加主鍵而不檢查MySQL中的AUTOINCREMENT

Question

如何增加主鍵而不檢查MySQL中的AUTOINCREMENT？

我的實施例：

Tax.java 
/* 
* To change this template, choose Tools | Templates 
* and open the template in the editor. 
*/ 
package newpackage; 

import java.io.Serializable; 
import java.math.BigDecimal; 
import java.util.List; 
import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.naming.Context; 
import javax.naming.InitialContext; 
import javax.persistence.*; 
import javax.transaction.UserTransaction; 
import javax.validation.constraints.NotNull; 
import javax.xml.bind.annotation.XmlRootElement; 
import javax.xml.bind.annotation.XmlTransient; 

/** 
* 
* @author gile 
*/ 
@Entity 
@Table(name = "tax", catalog = "invoicedb", schema = "") 
@XmlRootElement 
@NamedQueries({ 
    @NamedQuery(name = "Tax.findAll", query = "SELECT t FROM Tax t"), 
    @NamedQuery(name = "Tax.findByIdtax", query = "SELECT t FROM Tax t WHERE t.idtax = :idtax"), 
    @NamedQuery(name = "Tax.findByValue", query = "SELECT t FROM Tax t WHERE t.value = :value"), 
    **@NamedQuery(name = "Tax.findMaxID", query = "SELECT MAX (t.idtax) from Tax t")})** // I write this query to find max value of primary key. how to find max ? 
public class Tax implements Serializable { 
    private static final long serialVersionUID = 1L; 
    @Id 
    @Basic(optional = false) 
    @NotNull 
    @Column(name = "idtax") 
    private Integer idtax; 
    @Basic(optional = false) 
    @NotNull 
    @Column(name = "value") 
    private BigDecimal value; 
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "taxid") 
    private List<Invoicedetails> invoicedetailsList; 

    public Tax() { 
    } 

    public Tax(Integer idtax) { 
     this.idtax = idtax; 
    } 

    public Tax(Integer idtax, BigDecimal value) { 
     this.idtax = idtax; 
     this.value = value; 
    } 

    public Integer getIdtax() { 
     return idtax; 
    } 

    public void setIdtax(Integer idtax) { 
     this.idtax = idtax; 
    } 

    public BigDecimal getValue() { 
     return value; 
    } 

    public void setValue(BigDecimal value) { 
     this.value = value; 
    } 

    @XmlTransient 
    public List<Invoicedetails> getInvoicedetailsList() { 
     return invoicedetailsList; 
    } 

    public void setInvoicedetailsList(List<Invoicedetails> invoicedetailsList) { 
     this.invoicedetailsList = invoicedetailsList; 
    } 

    @Override 
    public int hashCode() { 
     int hash = 0; 
     hash += (idtax != null ? idtax.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 Tax)) { 
      return false; 
     } 
     Tax other = (Tax) object; 
     if ((this.idtax == null && other.idtax != null) || (this.idtax != null && !this.idtax.equals(other.idtax))) { 
      return false; 
     } 
     return true; 
    } 
    @Override 
    public String toString() { 
    return String.format("%.2f %%",value); 
    } 

    @Transient 
    private String taxvalueString; 

    public String getTaxvalueString() { 
     return String.format(" %.2f %%",value); 
    } 

    public void setTaxvalueString(String taxvalueString) { 
     this.taxvalueString = taxvalueString; 
    } 
} 

Answer 1

可以在稅分類與PrePersit註解添加的方法，用於創建PK（idtax）

像

@PrePersist 
private void generateID() { 
    // Read existing Tax record, finde new id and set pk here. 
}