JSP 中Hibernate实现映射枚举类型

jsp 中hibernate实现映射枚举类型

问题：

java bo类gender是枚举类型，想在数据库中存成字符串格式，如何编写hbm.xml？

public enum gender{  
 unknown("unknown"),  
 male("male"),  
 female("female"); 
   
 private string key; 
 private gender(final string key) { 
  this.key = key; 
 } 
 public getgender(string key) { 
  for (gender gender : gender.values()) { 
   if (key.euqals(gender.getkey())) 
    return gender;       
  } 
  throw new nosuchelementexception(key); 
 } 
} 

使用usertype：

public class genderusertype implements usertype {  
 
  private static int[] typelist = { types.varchar};  
 
 /* 
  * return the sql type codes for the columns mapped by this type. 
  * the codes are defined on <tt>java.sql.types</tt>. */ 
 /**设置和gender类的sex属性对应的字段的sql类型 */  
 public int[] sqltypes() { 
   return typelist; 
 } 
 
 /*the class returned by <tt>nullsafeget()</tt>.*/ 
 /** 设置genderusertype所映射的java类：gender类 */ 
 public class returnedclass() { 
   return gender.class;  
 }  
 
 /** 指明gender类是不可变类 */  
 public boolean ismutable() { 
   return false; 
 } 
 
 /* 
 * return a deep copy of the persistent state, stopping at entities and at 
 * collections. it is not necessary to copy immutable objects, or null 
 * values, in which case it is safe to simply return the argument. 
 */ 
 /** 返回gender对象的快照，由于gender类是不可变类， 因此直接将参数代表的gender对象返回 */  
 public object deepcopy(object value) {  
  return (gender)value;  
 }  
 
 /** 比较一个gender对象是否和它的快照相同 */ 
 public boolean equals(object x, object y) { 
  //由于内存中只可能有两个静态常量gender实例，  
  //因此可以直接按内存地址比较  
  return (x == y);  
 }  
 public int hashcode(object x){  
   return x.hashcode();  
 }  
 
 /* 
 * retrieve an instance of the mapped class from a jdbc resultset. implementors 
 * should handle possibility of null values. 
 */ 
 /** 从jdbc resultset中读取key，然后返回相应的gender实例 */ 
 public object nullsafeget(resultset rs, string[] names, object owner) 
               throws hibernateexception, sqlexception{  
   //从resultset中读取key 
   string sex = (string) hibernate.string.nullsafeget(rs, names[0]);  
   if (sex == null) { return null; }  
   //按照性别查找匹配的gender实例  
   try {  
    return gender.getgender(sex);  
   }catch (java.util.nosuchelementexception e) {  
    throw new hibernateexception("bad gender value: " + sex, e);  
   }  
 } 
 
 /* 
 * write an instance of the mapped class to a prepared statement. implementors 
 * should handle possibility of null values. 
 * a multi-column type should be written to parameters starting from <tt>index</tt>. 
 */ 
 /** 把gender对象的key属性添加到jdbc preparedstatement中 */ 
 public void nullsafeset(preparedstatement st, object value, int index)  
                throws hibernateexception, sqlexception{  
  string sex = null;  
  if (value != null)  
    sex = ((gender)value).getkey();  
  hibernate.string.nullsafeset(st, sex, index);  
 }  
 
 /* 
 * reconstruct an object from the cacheable representation. at the very least this 
 * method should perform a deep copy if the type is mutable. (optional operation) 
 */ 
 public object assemble(serializable cached, object owner){ 
   return cached; 
 }  
  
 /* 
   * transform the object into its cacheable representation. at the very least this 
   * method should perform a deep copy if the type is mutable. that may not be enough 
   * for some implementations, however; for example, associations must be cached as 
   * identifier values. (optional operation) 
  */ 
  public serializable disassemble(object value) { 
     return (serializable)value;  
  }  
 
 /* 
 * during merge, replace the existing (target) value in the entity we are merging to 
 * with a new (original) value from the detached entity we are merging. for immutable 
 * objects, or null values, it is safe to simply return the first parameter. for 
 * mutable objects, it is safe to return a copy of the first parameter. for objects 
 * with component values, it might make sense to recursively replace component values. 
 */ 
 public object replace(object original, object target, object owner){ 
    return original;  
 }  
} 

然后再hbm.xml中定义映射关系：

<hibernate-mapping package="" default-lazy="true" default-cascade="save-update,merge,persist"> 
  <typedef name="gender" class="com.alpha.hibernate.genderusertype"> 
    <property name="gender" type="gender"> 
        <column name="gender" not-null="true"> 
        </column> 
    </property> 

延伸：

为每个枚举类型定义一个usertype是比较麻烦的，可以定义一个抽象类。

例如扩展下例即可适用于所有保存为index的枚举类型

public abstract class ordinalenumusertype<e extends enum<e>> implements usertype {  
 
  protected class<e> clazz; 
   
  protected ordinalenumusertype(class<e> clazz) { 
    this.clazz = clazz; 
  }  
  
  private static final int[] sql_types = {types.numeric};  
  public int[] sqltypes() {  
    return sql_types;  
  }  
  
  public class<?> returnedclass() {  
    return clazz;  
  }  
  
  public e nullsafeget(resultset resultset, string[] names, object owner)  
               throws hibernateexception, sqlexception {     
 
    //hibernate.string.nullsafeget(rs, names[0]) 
    int index = resultset.getint(names[0]); 
    e result = null;  
    if (!resultset.wasnull()) {  
      result = clazz.getenumconstants()[index];  
    }  
    return result;  
  }  
  
  public void nullsafeset(preparedstatement preparedstatement, 
     object value,int index) throws hibernateexception, sqlexception {  
    if (null == value) {  
      preparedstatement.setnull(index, types.numeric);  
    } else {  
      //hibernate.string.nullsafeset(st, sex, index); 
      preparedstatement.setint(index, ((e)value).ordinal());  
    }  
  }  
  
  public object deepcopy(object value) throws hibernateexception{  
    return value;  
  }  
  
  public boolean ismutable() {  
    return false;  
  }  
  
  public object assemble(serializable cached, object owner)  
throws hibernateexception { 
     return cached; 
  }  
 
  public serializable disassemble(object value) throws hibernateexception {  
    return (serializable)value;  
  }  
  
  public object replace(object original, object target, object owner) 
throws hibernateexception {  
    return original;  
  }  
  public int hashcode(object x) throws hibernateexception {  
    return x.hashcode();  
  }  
  public boolean equals(object x, object y) throws hibernateexception {  
    if (x == y)  
      return true;  
    if (null == x || null == y)  
      return false;  
    return x.equals(y);  
  }  
} 

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！