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## oracle.jbo.server
Class SequenceImpl

`java.lang.Object
oracle.jbo.server.SequenceImpl`

All Implemented Interfaces:
  DomainInterface, java.io.Serializable

public class SequenceImpl
extends java.lang.Object
implements DomainInterface, java.io.Serializable

An encapsulation of a database sequence. This class provides a Java wrapper for a database sequence and may be used whenever it is necessary to query sequence values from a database sequence. See the discussion below for more information on using this class to query database sequences instead of instantiating a dynamic View Object.

### Creating View Objects and Generating Sequence Numbers

If you use `createViewObjectFromQueryStmt` to create View Objects that query database sequences, do not depend on the view object to correctly generate sequence numbers. The process of querying the View Object for sequence numbers causes sequence numbers to be generated twice. For example, if you create a View Object from a query statement which gets the next value from a sequence:

      String sqlStr = "SELECT CRM_INT_PROCESSES_SEQ.NEXTVAL FROM DUAL ";
      ViewObject View0 =appMod.createViewObjectFromQueryStmt("SeqView", sqlStr);
      Row idRow = View0.first();

When `View0.first()` (or `last()`, for that matter) is executed, the query is executed twice and sequence numbers are lost. Setting the View Object to `setForwardOnly` also has no effect.

This problem is caused by a JDBC bug that forces "prefetch" to be greater than or equal to 1. That is, when you execute the query for the View Object, it fetches at least one row before you call `next()`. This is why the sequence number increases by two.

Instead of instantiating a View Object, explicitly create a new sequence:

     import oracle.jbo.server.SequenceImpl;
      .
      .
      SequenceImpl s = new SequenceImpl(sequenceName, thisTransaction);
        Number sVal = s.getSequenceNumber();
      .
      .
        setYourSequenceAttribute(sVal);
      .

Since:
  Jdeveloper 3.0
See Also:
  `ViewObject`, `DBTransaction`, `ApplicationModule`, Serialized Form

Constructor Summary
`SequenceImpl()`
`SequenceImpl(java.lang.String seqName, ApplicationModule am)` Constructor.
`SequenceImpl(java.lang.String seqName, DBTransaction trans)` Constructor.

Method Summary
`static java.lang.Object` | `createInstanceWithAM(java.lang.String seqName, ApplicationModule am)` A class method that may be invoked to retrieve the next value from a database sequence.
`boolean` | `equals(java.lang.Object other)` Test if the specified value is equal to `this` SequenceImpl object.
`java.lang.Object` | `getData()` Internal: Applications should not use this method. Returns a sequence value.
`Number` | `getSequenceNumber()` Returns a sequence value.
`int` | `hashCode()` Computes a hash code for `this` SequenceImpl object.
`void` | `setContext(DomainOwnerInterface owner, Transaction trans, java.lang.Object ctx)` Internal: Applications should not use this method.
`java.lang.String` | `toString()` For testing purposes only: Returns a string representation of the generated sequence value.

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Constructor Detail

### SequenceImpl

    public SequenceImpl()

### SequenceImpl

    public SequenceImpl(java.lang.String seqName,
                        ApplicationModule am)

  Constructor.
Parameters:
  `seqName` - The name of the database sequence that will be used to generate sequence values.
  `am` - The application module instance that will provide the JDBC connection for the sequence requests.

### SequenceImpl

    public SequenceImpl(java.lang.String seqName,
                        DBTransaction trans)

  Constructor.
Parameters:
  `seqName` - The name of the database sequence that will be used to generate sequence values.
  `trans` - The Transaction instance that will provide the JDBC connection for the sequence requests.

Method Detail

### createInstanceWithAM

    public static java.lang.Object createInstanceWithAM(java.lang.String seqName,
                                                        ApplicationModule am)

  A class method that may be invoked to retrieve the next value from a database sequence.
  Parameters:
    `seqName` - The name of the database sequence that will be used to generate the sequence value.
    `am` - The application module instance that will provide the JDBC connection for the sequence request

### getData

    public java.lang.Object getData()

  Internal: Applications should not use this method. Returns a sequence value. The sequence value is generated by the database sequence that was specified when constructing the SequenceImpl object.

  This method will increment the encapsulated database sequence the first time that it is invoked. Subsequent calls will return the same value.

  Specified by:
    `getData` in interface `DomainInterface`
  Returns:
    An object representing the next sequence value.

### getSequenceNumber

    public Number getSequenceNumber()

  Returns a sequence value. The sequence value is generated by the database sequence that was specified when constructing the SequenceImpl object.

  This method will increment the encapsulated database sequence the first time that it is invoked. Subsequent calls will return the same value.

  Returns:
    An instance of oracle.jbo.domain.Number representing the next sequence value.

### setContext

    public void setContext(DomainOwnerInterface owner,
                           Transaction trans,
                           java.lang.Object ctx)

  Internal: Applications should not use this method.
  Specified by:
    `setContext` in interface `DomainInterface`

### toString

    public java.lang.String toString()

  For testing purposes only: Returns a string representation of the generated sequence value.

### equals

    public boolean equals(java.lang.Object other)

  Test if the specified value is equal to `this` SequenceImpl object.
  Parameters:
    `other` - The object to which the SequenceImpl should be compared.
  Returns:
    true The specified object is equal to the `this` SequenceImpl.

### hashCode

    public int hashCode()

  Computes a hash code for `this` SequenceImpl object.
  Returns:
    the hash code of `this` SequenceImpl object.

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