如何使用列名作为键将某些表列映射到Map [英] How to map some table columns to a Map with the column names as key
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问题描述
我有这张桌子:
CREATE TABLE user_type (
id TINYINT NOT NULL AUTO_INCREMENT,
name VARCHAR(20) UNIQUE NOT NULL,
...
--Some more columns
can_create BOOLEAN NOT NULL,
can_edit BOOLEAN NOT NULL,
can_delete BOOLEAN NOT NULL,
...
--Has 23 more columns that define different permissions
PRIMARY KEY (id)
);
并希望将其映射到这样的内容:
And would like to map it to something like this:
@Entity
@Table(name = "user_type")
public class UserType{
@Id
private Byte id;
private String name;
// Some more fields
//Then this map should contain the remaining 26 permission columns
//with the column names (can_create, can_edit, etc.) as keys.
@???
private Map<String, Boolean> permissions;
}
是否可以像这样将某些列映射到 Map
?在所有示例和问题中,我发现它们只是将两个值映射在一起,而不是带有其值的列名称.
Is it possible to map some columns to a Map
like that? In all the examples and questions I found they just map two values together, not a column name with its value.
推荐答案
您可以尝试使用以下方法.
You can try to use the following approach.
- 创建一个代表您的权限类型的枚举:
public enum PermissionType
{
CREATE,
EDIT,
DELETE
// other permissions ...
}
- 创建
Permissions
类,该类将保留用户的权限状态.
- Create
Permissions
class that will hold the permissions state for a user.
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
public class Permissions implements Serializable
{
private Map<PermissionType, Boolean> permissions;
public Permissions()
{
permissions = new HashMap<>(PermissionType.values().length);
for (PermissionType permType : PermissionType.values())
{
permissions.put(permType, false);
}
}
public void setPermission(PermissionType name, Boolean value)
{
permissions.put(name, value);
}
public Map<PermissionType, Boolean> getPermissions()
{
return permissions;
}
@Override
public int hashCode()
{
return permissions.hashCode();
}
@Override
public boolean equals(Object obj)
{
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
Permissions other = (Permissions) obj;
return Objects.equals(other.permissions, permissions);
}
}
- 创建休眠自定义基本类型通过以下方式获取
Permissions
:
- Create hibernate custom basic type for the
Permissions
in the following way:
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Map;
import java.util.Objects;
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.usertype.UserType;
public class PermissionUserType implements UserType
{
private static final int[] SQL_TYPES;
static {
SQL_TYPES = new int[PermissionType.values().length];
for (int ind = 0; ind < SQL_TYPES.length; ind++)
{
SQL_TYPES[ind] = Types.BOOLEAN;
}
}
@Override
public int[] sqlTypes()
{
return SQL_TYPES;
}
@Override
public Class<?> returnedClass()
{
return Permissions.class;
}
@Override
public boolean equals(Object x, Object y) throws HibernateException
{
return Objects.equals(x, y);
}
@Override
public int hashCode(Object x) throws HibernateException
{
return Objects.hashCode(x);
}
@Override
public Permissions nullSafeGet(ResultSet rs, String[] names, SharedSessionContractImplementor session, Object owner) throws HibernateException, SQLException
{
/*
* The names are column aliases generated by hibernate, like can_dele5_5_, can_crea3_5_, ...
**/
Permissions permissions = new Permissions();
for (int ind = 0; ind < names.length; ind++)
{
Boolean val = rs.getBoolean(names[ind]);
PermissionType name = PermissionType.values()[ind];
permissions.setPermission(name, val);
}
return permissions;
}
@Override
public void nullSafeSet(PreparedStatement st, Object value, int index, SharedSessionContractImplementor session) throws HibernateException, SQLException
{
if (Objects.isNull(value))
{
for (int ind = 0; ind < SQL_TYPES.length; ind++)
{
st.setNull(index + ind, SQL_TYPES[ind]);
}
}
else
{
Permissions permissions = (Permissions) value;
for (Map.Entry<PermissionType, Boolean> permEntry : permissions.getPermissions().entrySet())
{
Integer ind = permEntry.getKey().ordinal();
st.setObject(index + ind, permEntry.getValue(), SQL_TYPES[ind]);
}
}
}
@Override
public Permissions deepCopy(Object value) throws HibernateException
{
if (value == null) return null;
Permissions oldPerms = (Permissions) value;
Permissions newPerms = new Permissions();
for (Map.Entry<PermissionType, Boolean> permEntry : oldPerms.getPermissions().entrySet())
{
newPerms.setPermission(permEntry.getKey(), permEntry.getValue());
}
return newPerms;
}
@Override
public boolean isMutable()
{
return false;
}
@Override
public Serializable disassemble(Object value) throws HibernateException
{
return deepCopy(value);
}
@Override
public Object assemble(Serializable cached, Object owner) throws HibernateException
{
return deepCopy(cached);
}
@Override
public Object replace(Object original, Object target, Object owner) throws HibernateException
{
return deepCopy(original);
}
}
- 然后在您的实体映射中使用此自定义基本类型:
import org.hibernate.annotations.Columns;
import org.hibernate.annotations.Type;
@Entity
@Table(name = "user_type")
public class UserTypeEntity
{
@Id
@Column(name = "id")
private Long id;
@Column(name = "name")
private String name;
@Type(type = "com.me.PermissionUserType")
@Columns(columns = {
// the order should be matched with the enum PermissionType
@Column(name = "can_create"),
@Column(name = "can_edit"),
@Column(name = "can_delete")
})
private Permissions permissions;
// ...
}
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