net.sf.duro

Class DSession

java.lang.Object

net.sf.duro.DSession

Direct Known Subclasses:

LocalSession

public abstract class DSession
extends java.lang.Object

The central class used by Java applications to access DuroDBMS.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	DSession()

Method Summary

Modifier and Type	Method and Description
void	close() Closes the session.
static DSession	createSession() Creates a local DSession.
static DSession	createSession(java.net.URL url) Creates a remote DSession.
abstract java.lang.Object	evaluate(java.lang.String expr) Evaluates a Duro D/T expression.
abstract <T> T	evaluate(java.lang.String expr, java.lang.Class<T> destClass) Evaluates expr, stores the result in an instance of class destClass and returns that instance.
abstract void	evaluate(java.lang.String expr, java.lang.Object dest) Evaluates the expression expr and stores the value in dest.
abstract void	execute(java.lang.String code) Executes Duro D/T code.
abstract void	setVar(java.lang.String name, java.lang.Object v) Assigns a value to a variable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DSession

protected DSession()

Method Detail

createSession

public static DSession createSession()

Creates a local DSession.

Returns:

the DSession created.

Throws:

DException - if a Duro error occurs

createSession

public static DSession createSession(java.net.URL url)

Creates a remote DSession. The URL must be as follows: :[port]//database

Returns:

the DSession created.

Throws:

DException

close

public void close()

Closes the session.

Throws:

DException - If a Duro error occurs

execute

public abstract void execute(java.lang.String code)

Executes Duro D/T code.

User-defined operators implemented in Java can be created by using the OPERATOR statement with the EXTERN keyword.

Creating a user-defined read-only operator implemented by a Java method:

OPERATOR <opname>(<parameter_list>) RETURNS <type>
EXTERN 'Java' '<classname>.<methodname>';
END OPERATOR;

The method must be static. Parameter types and return type map to Java types as described in evaluate.

Creating a user-defined update operator implemented by a Java method:

OPERATOR <opname>(<parameter_list>) UPDATES { <update_param_list> }
EXTERN 'Java' '<classname>.<methodname>';
END OPERATOR;

The method must be static. Non-update parameter types map to Java types as described in evaluate. Update parameter types map to Java classes as follows:

boolean

UpdatableBoolean

string

java.lang.StringBuilder

integer

UpdatableInteger

float

UpdatableDouble

binary

ByteArray

tuple { ... }

Tuple

relation { ... }

java.util.Set

array

java.util.ArrayList

types with declared possible representations

PossrepObject

Parameters:

code - The code to execute

Throws:

DException - If the code could not be executed.

evaluate

public abstract java.lang.Object evaluate(java.lang.String expr)

Evaluates a Duro D/T expression.

Duro types map to Java classes as follows:

boolean

java.lang.Boolean

string

java.lang.String

integer

java.lang.Integer

float

java.lang.Double

binary

byte[]

tuple { ... }

Tuple

relation { ... }

java.util.Set

array

Duro arrays map to Java arrays. For example, array integer is converted to java.lang.Integer[].

types with declared possible representations

PossrepObject

Parameters:

expr - The expression to evaluate

Returns:

an object representing the result value.

Throws:

DException - If the expression could not be evaluated.

evaluate

public abstract void evaluate(java.lang.String expr,
                              java.lang.Object dest)

Evaluates the expression expr and stores the value in dest. The type of expr must have possreps and dest must have a setter for each property.

Parameters:

expr - the expression to evaluate

dest - the destination object

Throws:

DException

evaluate

public abstract <T> T evaluate(java.lang.String expr,
                               java.lang.Class<T> destClass)

Evaluates expr, stores the result in an instance of class destClass and returns that instance. If destClass is an interface, a dynamic proxy is created. Otherwise, the default constructor of destClass is called.

Parameters:

expr - the expression to evaluate

destClass - the class or interface the returned object is an instance of.

Returns:

an object of class destClass representing the result value.

Throws:

DException

setVar

public abstract void setVar(java.lang.String name,
                            java.lang.Object v)

Assigns a value to a variable.

Parameters:

name - The name of the variable

v - The value

Throws:

DException - If a Duro error occurs.

java.lang.IllegalArgumentException - If v does not match the type of the variable.