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I really can't find a nice enum JDBC mapping example. Is enum actually supported by JDBC?
I am working with MySQL. I have an enum column, and would like to map to some Java enum.
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In Java (from 1.5), enums are represented using enum data type. Java enums are more powerful than C/C++ enums. In Java, we can also add variables, methods, and constructors to it. The main objective of enum is to define our own data types(Enumerated Data Types).
In Java you cannot pass any parameters by reference. The only workaround I can think of would be to create a wrapper class, and wrap an enum. Now, reference will contain a different value for your enum; essentially mimicking pass-by-reference.
In MySQL, an ENUM is a string object whose value is chosen from a list of permitted values defined at the time of column creation. The ENUM data type provides the following advantages: Compact data storage. MySQL ENUM uses numeric indexes (1, 2, 3, …) to represents string values.
An enum is a special "class" that represents a group of constants (unchangeable variables, like final variables). To create an enum , use the enum keyword (instead of class or interface), and separate the constants with a comma.
JDBC does not support enums.
You can convert a string to an enum though, so if you have a Java enum you can do something like
MyEnum enumVal = MyEnum.valueOf(rs.getString("EnumColumn")); You'll have to keep your java enum and mysql enum in sync though. MyEnum.valueOf() can throw IllegalArgumentException if there's no mapping from the string, or NullPointerException if you get a null value from the db.
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Here is some generic solution were are using in converting JDBC values to Java enums.
param = Enum.valueOf((Class<? extends Enum>)dbField.getField().getType(), (String) param); where param is the value of the field in the db , and the dbField is the java.reflect.util.Field , where to put the value to
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