如何使用hibernate生成Custom Id，同时它必须是表的主键

这是我的pojo课程

@Entity public class Department { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) @Column(name="Department_Id") private Integer deptId; @Column(name="Department_Name",unique=true,nullable=false) private String deptName; @Column(name="Department_Description") @NotNull private String deptDesc; //geters and setters 

我想要的是department_id必须是此Department表的主键，此键的条目必须为DEP0001，DEP0002，DEP0003

Answer 1

谢谢大家的回复……最后我在我的Department类中做了一些更改并使用了一个类来生成id ……..这是我的代码

 @Entity public class Department { @Id @GenericGenerator(name = "sequence_dep_id", strategy = "com.xyz.ids.DepartmentIdGenerator") @GeneratedValue(generator = "sequence_dep_id") @Column(name="Department_Id") private String deptId; @Column(name="Department_Name",unique=true,nullable=false) private String deptName; @Column(name="Department_Description") @NotNull private String deptDesc; //getters and setters 

DepartmentIdGenerator.java

 package com.xyz.ids; import java.io.Serializable; import java.sql.*; import org.hibernate.HibernateException; import org.hibernate.engine.spi.SessionImplementor; import org.hibernate.id.IdentifierGenerator; public class DepartmentIdGenerator implements IdentifierGenerator{ @Override public Serializable generate(SessionImplementor session, Object object) throws HibernateException { String prefix = "DEP"; Connection connection = session.connection(); try { Statement statement=connection.createStatement(); ResultSet rs=statement.executeQuery("select count(Department_Id) as Id from demo.Department"); if(rs.next()) { int id=rs.getInt(1)+101; String generatedId = prefix + new Integer(id).toString(); System.out.println("Generated Id: " + generatedId); return generatedId; } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } } 

Answer 2

在Hibernate中实现自定义id生成器的最佳方法。

 @Entity @Table(name = "employee_customid") public class Employee implements Serializable { @Id @GenericGenerator(name = "string_based_custom_sequence", strategy = "com.ie.customid.EmployeeIdGenerator") @GeneratedValue(generator = "string_based_custom_sequence") @Column(name = "custom_emp_id") private String id; @Column(name = "emp_name") private String name; @Column(name = "emp_age") private Integer age; @Column(name = "emp_salary") private Double salary; // getter setter and toString 

下面的代码是用于在hibernate中生成自定义id的实现，任何数据库代码都是相同的（只需极少的更改）

 package com.ie.customid; import org.hibernate.HibernateException; import org.hibernate.engine.spi.SessionImplementor; import org.hibernate.id.IdentifierGenerator; import java.io.Serializable; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class EmployeeIdGenerator implements IdentifierGenerator { //You can give any name to sequence be sure that you know how to use it. private final String DEFAULT_SEQUENCE_NAME = "hibernate_sequence"; //private final String DEFAULT_SEQUENCE_NAME = "hib_sequence"; /* * This method will generate custom id based on String followed by id * eg emp0001, emp0002, emp0003 and so on.. * */ public Serializable generate(SessionImplementor session, Object object) throws HibernateException { Serializable result = null; Connection connection = null; Statement statement = null; ResultSet resultSet = null; String prefix = "emp"; try { connection = session.connection(); statement = connection.createStatement(); try { /* * uncomment below line if you are using mysql and the sequence DOES NOT EXIST. * As we all know MySql does not support sequence, instead there is AUTO INCREMENT * if you are using other databases change SQL according to that * eg Oracle: "SELECT "+sequenceName+".NEXTVAL FROM DUAL" * PostgreSQL: "SELECT NEXTVAL('+sequenceName+"') * */ //statement.executeUpdate("UPDATE " + DEFAULT_SEQUENCE_NAME + " SET next_val=LAST_INSERT_ID(next_val+1)"); resultSet = statement.executeQuery("SELECT next_val FROM " + DEFAULT_SEQUENCE_NAME); } catch (Exception e) { System.out.println("In catch, cause : Table is not available."); // if sequence is not found then creating the sequence // Below code is for MySql database you change according to your database statement.execute("CREATE table " + DEFAULT_SEQUENCE_NAME + " (next_val INT NOT NULL)"); statement.executeUpdate("INSERT INTO " + DEFAULT_SEQUENCE_NAME + " VALUES(0)"); //==> LAST_INSERT_ID(next_val+1) -> this is inbuilt function of MySql so by using this we can achieve our custom sequence like auto increment statement.executeUpdate("UPDATE " + DEFAULT_SEQUENCE_NAME + " SET next_val=LAST_INSERT_ID(next_val+1)"); resultSet = statement.executeQuery("SELECT next_val FROM " + DEFAULT_SEQUENCE_NAME); //e.printStackTrace(); } if (resultSet.next()) { int nextValue = resultSet.getInt(1); String suffix = String.format("%04d", nextValue); result = prefix.concat(suffix); System.out.println("Custom generated sequence is : " + result); } } catch (SQLException e) { e.printStackTrace(); } return result; } } 

如果您想使用XML配置，请使用下面的代码

     update org.hibernate.dialect.MySQLDialect jdbc:mysql://localhost:3306/Testing root root true true com.mysql.jdbc.Driver      

下面是Employee映射文件