java - 无法找到类 Spring Enum Mybatis 异常的可用构造函数

Question

我正在尝试在 spring mybatis 中设置 ENUM TypeHandlers，出现以下异常，

Cause: org.apache.ibatis.type.TypeException: Unable to find a usable constructor for class com.citi.aw.data.ibatis.KnownTypeHandlers$PortfolioTypeEnum

SQLConfig.xml

<configuration>
 <typeHandlers>
    <typeHandler javaType="com.citi.aw.entities.portfolio.PortfolioType" 
        handler="com.citi.aw.data.ibatis.KnownTypeHandlers$PortfolioTypeEnum"/></typeHandlers>
</configuration>

投资组合类型枚举

public enum PortfolioType
{
    PROPOSAL,
    INVESTABLE,
    MODEL,
    MODEL_STRATEGY,
    STRATEGY,
    CLIENT,
    FUND_OF_FUND,
    REFERENCE,
    MODEL_ALLOCATION    
}

---

Class KnownTypeHandlers
 public class KnownTypeHandlers 
    {
        public static abstract class PortfolioTypeEnum extends OrdinalEnumTypeHandler
        {
            public PortfolioTypeEnum()
            {
                super(PortfolioType.values());
            }
        }
}

---

Class OrdinalEnumTypeHandler

    public abstract class OrdinalEnumTypeHandler extends org.apache.ibatis.type.BaseTypeHandler<Object>
{
    private Object[] enumValues;

    protected OrdinalEnumTypeHandler(Object[] enumValues)
    {
        this.enumValues = enumValues;
    }

    @Override
    public Object getResult(ResultSet rs, String columnName) throws SQLException
    {
        int intValue = rs.getInt(columnName);
        return enumValues[intValue];
    }

    @Override
    public Object getResult(ResultSet rs, int columnPos) throws SQLException
    {
        int intValue = rs.getInt(columnPos);
        return enumValues[intValue];
    }

    @Override
    public Object getResult(CallableStatement arg0, int arg1) throws SQLException
    {
        throw new SQLException("not implemented");
    }

    @SuppressWarnings("unchecked")
    //@Override
    public void setParameter(PreparedStatement ps, int pos, Object parameter, String jdbcType) throws SQLException
    {
        ps.setInt(pos, ((Enum)parameter).ordinal());
    }

    //@Override
    public Object valueOf(String stringValue)
    {
        return enumValues[Integer.parseInt(stringValue)];
    }
}

Answer 1

我猜你正在使用 MyBatis 3。所以，你不需要为枚举创建任何处理程序。 MyBatis 有一个 typehandler 来处理 Enum 的情况。

搜索 MyBatis 3 Configuration在引用文档中:

typeHandlers

Whenever MyBatis sets a parameter on a PreparedStatement or retrieves a value from a ResultSet, a TypeHandler is used to retrieve the value in a means appropriate to the Java type. The following table describes the default TypeHandlers.

...

EnumTypeHandler - Enumeration Type - VARCHAR any string compatible type, as the code is stored (not index).

然后添加到您的配置 xml(在您的情况下 SqlConfig.xml:

<!-- mybatis-config.xml -->
<typeHandlers>
  <typeHandler handler="org.apache.ibatis.type.EnumTypeHandler"/>
</typeHandlers>