✅ Parameter Binding

✅ Converter names

Converter can get names, e.g. @JavaToJdbc("name"). They can only be used by an annotation @JdbcConverterName("name") on a parameter. Names are unique per scope.

✅ Marker

The Java method parameters are mapped by their names to the corresponding JDBC named parameter markers. The name in the JDBC string and in the Java code must be equal according UTF-8. All JDBC named parameter markers must be defined in the Java method and vice versa. Too many or too few parameters will lead to errors. JDBC support ’?’ as parameter markers. Kaumei JDBC does not support ’?’. It uses named parameter markers, every name is prefixed with ’:’, e.g. :name

• Each :name must match a method parameter. Parameters that do not appear in SQL are ignored.

✅ JDBC basic types

The following JDBC Java types are mapped by default to the PreparedStatement.set... methods:

• java.lang.String, java.math.BigDecimal boolean, byte, short, int, long, float, double, byte[], java.sql.Date, java.sql.Time, java.sql.Timestamp, java.sql.Clob, java.sql.Blob, java.sql.Array, java.sql.Ref, java.net.URL, java.sql.RowId, java.sql.NClob, java.sql.SQLXML
• java.sql.Struct (via setObject)
• In additional the following are supported by a default converter which maps to the underlying PreparedStatement method:
  • java.lang.Boolean, java.lang.Byte, java.lang.Short, java.lang.Integer, java.lang.Long, java.lang.Float, java.lang.Double
  • char, java.lang.Character (via setString)
• Some JDBC driver do not support all native JDBC types, please check the documentation of your driver.

✅ Java default converter

• Records with a single component of a JDBC-supported type automatically gain a converter, if no converter is defined for the record.
• Enums will get automatic a converter with convert it to the name, if no converter is defined for the record.

✅ Custom converter

we can define converter to set JDBC values from Java

• ✅ A static simple converter which converts a value T into a supported JDBC value R: static R toDB(T value)
  • Parameter and return must be unspecific or nonnull.
  • The method must be annotated with @JavaToJdbc
• ✅ A static JDBC converter which sets a value R on a given PreparedStatement: static void toDB(PreparedStatement stmt, int index, T value) The parameter value must be nullable or unspecific. The method must handel null correctly. The method must be annotated with @JavaToJdbc
• ✅ A object method which is annotated with @JavaToJdbc and returns the object value as JDBC value. The return value must be be unspecific or nonnull.

✅ Collections

Arrays and single-parameter collections are expand to repeated ? placeholders via ResultSetUtils.marks, inserting one entry per element.

• Nullable collections/arrays are not allowed
• Nullable markers for the values if the collections are allowed
• Nullable markers for the primitives in arrays are ignored