Wrapper (Java Platform SE 8 )
Keywords: java.sql.Wrapper interface
Date: 2016-04-24

compact2, compact3
java.sql

## Interface Wrapper

- All Known Subinterfaces:
    CachedRowSet, CallableStatement, Connection, DatabaseMetaData, DataSource, FilteredRowSet, JdbcRowSet, JoinRowSet, ParameterMetaData, PreparedStatement, ResultSet, ResultSetMetaData, RowSet, RowSetMetaData, Statement, SyncResolver, WebRowSet
  All Known Implementing Classes:
    RowSetMetaDataImpl

      public interface Wrapper

  Interface for JDBC classes which provide the ability to retrieve the delegate instance when the instance in question is in fact a proxy class.

  The wrapper pattern is employed by many JDBC driver implementations to provide extensions beyond the traditional JDBC API that are specific to a data source. Developers may wish to gain access to these resources that are wrapped (the delegates) as proxy class instances representing the the actual resources. This interface describes a standard mechanism to access these wrapped resources represented by their proxy, to permit direct access to the resource delegates.

  Since:
    1.6

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `isWrapperFor(Class<?> iface)` Returns true if this either implements the interface argument or is directly or indirectly a wrapper for an object that does.
    `<T> T` | `unwrap(Class<T> iface)` Returns an object that implements the given interface to allow access to non-standard methods, or standard methods not exposed by the proxy.

- - ### Method Detail

    - #### unwrap

          <T> T unwrap(Class<T> iface)
                throws SQLException

      Returns an object that implements the given interface to allow access to non-standard methods, or standard methods not exposed by the proxy. If the receiver implements the interface then the result is the receiver or a proxy for the receiver. If the receiver is a wrapper and the wrapped object implements the interface then the result is the wrapped object or a proxy for the wrapped object. Otherwise return the the result of calling `unwrap` recursively on the wrapped object or a proxy for that result. If the receiver is not a wrapper and does not implement the interface, then an `SQLException` is thrown.
      Type Parameters:
        `T` - the type of the class modeled by this Class object
      Parameters:
        `iface` - A Class defining an interface that the result must implement.
      Returns:
        an object that implements the interface. May be a proxy for the actual implementing object.
      Throws:
        `SQLException` - If no object found that implements the interface
      Since:
        1.6

    - #### isWrapperFor

          boolean isWrapperFor(Class<?> iface)
                        throws SQLException

      Returns true if this either implements the interface argument or is directly or indirectly a wrapper for an object that does. Returns false otherwise. If this implements the interface then return true, else if this is a wrapper then return the result of recursively calling `isWrapperFor` on the wrapped object. If this does not implement the interface and is not a wrapper, return false. This method should be implemented as a low-cost operation compared to `unwrap` so that callers can use this method to avoid expensive `unwrap` calls that may fail. If this method returns true then calling `unwrap` with the same argument should succeed.
      Parameters:
        `iface` - a Class defining an interface.
      Returns:
        true if this implements the interface or directly or indirectly wraps an object that does.
      Throws:
        `SQLException` - if an error occurs while determining whether this is a wrapper for an object with the given interface.
      Since:
        1.6

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