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Appendix A

Servlet and JSP Quick Reference

HttpSession Methods

  public Object getValue(String name) [2.1]

public Object getAttribute(String name) [2.2] 

Extracts a previously stored value from a session object. Returns 

null

 if 

no value is associated with given name.

  public void putValue(String name, Object value) [2.1]

public void setAttribute(String name, Object value) [2.2] 

Associates a value with a name. If value implements 

HttpSessionBindingListener

, its 

valueBound

 method is called. If 

previous value implements 

HttpSessionBindingListener

, its 

valueUnbound

 method is called.

  public void removeValue(String name) [2.1]

public void removeAttribute(String name) [2.2] 

Removes any values associated with designated name. If value being 

removed implements 

HttpSessionBindingListener

, its 

valueUnbound

 method is called.

  public String[] getValueNames() [2.1]

public Enumeration getAttributeNames() [2.2] 

Returns the names of all attributes in the session.

  public String getId() 

Returns the unique identifier generated for each session.

  public boolean isNew() 

Returns 

true

 if the client (browser) has never seen the session; 

false

otherwise.

  public long getCreationTime() 

Returns time at which session was first created (in milliseconds since 

1970). To get a value useful for printing, pass value to 

Date

 constructor 

or the 

setTimeInMillis

 method of 

GregorianCalendar

. 

  public long getLastAccessedTime() 

Returns time at which the session was last sent from the client. 

  public int getMaxInactiveInterval() 

public void setMaxInactiveInterval(int seconds) 

Gets or sets the amount of time, in seconds, that a session should go 

without access before being automatically invalidated. A negative value 

indicates that session should never time out. Not the same as cookie 

expiration date.

  public void invalidate() 

Invalidates the session and unbinds all objects associated with it.

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