Package groovy.servlet

# Class ServletBinding

java.lang.Object
groovy.lang.GroovyObjectSupport
groovy.lang.Binding
groovy.servlet.ServletBinding

All Implemented Interfaces:
  `GroovyObject`

    public class ServletBinding
    extends Binding

Servlet-specific binding extension to lazy load the writer or the output stream from the response.

### Eager variables

- `"request"` : the `HttpServletRequest` object
- `"response"` : the `HttpServletRequest` object
- `"context"` : the `ServletContext` object
- `"application"` : same as context
- `"session"` : shorthand for `request.getSession(`false`)` - can be null!
- `"params"` : map of all form parameters - can be empty
- `"headers"` : map of all `request` header fields

### Lazy variables

- `"out"` : `response.getWriter()`
- `"sout"` : `response.getOutputStream()`
- `"html"` : `new MarkupBuilder(response.getWriter())` - `expandEmptyElements` flag is set to true
- `"json"` : `new JsonBuilder()`

As per the Servlet specification, a call to `response.getWriter()` should not be done if a call to `response.getOutputStream()` has already occurred or the other way around. You may wonder then how the above lazy variables can possibly be provided - since setting them up would involve calling both of the above methods. The trick is catered for behind the scenes using lazy variables. Lazy bound variables can be requested without side effects; under the covers the writer and stream are wrapped. That means `response.getWriter()` is never directly called until some output is done using 'out' or 'html'. Once a write method call is done using either of these variable, then an attempt to write using 'sout' will cause an `IllegalStateException`. Similarly, if a write method call on 'sout' has been done already, then any further write method call on 'out' or 'html' will cause an `IllegalStateException`.

### Reserved internal variable names (see "Methods" below)

- `"forward"`
- `"include"`
- `"redirect"`

If `response.getWriter()` is called directly (without using out), then a write method call on 'sout' will not cause the `IllegalStateException`, but it will still be invalid. It is the responsibility of the user of this class, to not to mix these different usage styles. The same applies to calling `response.getOutputStream()` and using 'out' or 'html'.

### Methods

- `"forward(String path)"` : `request.getRequestDispatcher(path).forward(request, response)`
- `"include(String path)"` : `request.getRequestDispatcher(path).include(request, response)`
- `"redirect(String location)"` : `response.sendRedirect(location)`

- ## Constructor Summary

  Constructors
  Constructor | Description
  --- | ---
  `ServletBinding​(HttpServletRequest request, HttpServletResponse response, ServletContext context)` | Initializes a servlet binding.

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `void` | `forward​(String path)` |
  `Object` | `getVariable​(String name)` |
  `Map` | `getVariables()` |
  `void` | `include​(String path)` |
  `void` | `redirect​(String location)` |
  `void` | `setVariable​(String name, Object value)` | Sets the value of the given variable

  ### Methods inherited from class groovy.lang.Binding

  `getProperty, hasVariable, removeVariable, setProperty`

  ### Methods inherited from class groovy.lang.GroovyObjectSupport

  `getMetaClass, setMetaClass`

  ### Methods inherited from class java.lang.Object

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

  ### Methods inherited from interface groovy.lang.GroovyObject

  `invokeMethod`

- ## Constructor Details

  - ### ServletBinding

    public ServletBinding​(HttpServletRequest request, HttpServletResponse response, ServletContext context)
    Initializes a servlet binding.
    Parameters:
      `request` - the HttpServletRequest object
      `response` - the HttpServletRequest object
      `context` - the ServletContext object

- ## Method Details

  - ### setVariable

    public void setVariable​(String name, Object value)
    Description copied from class: `Binding`
    Sets the value of the given variable
    Overrides:
      `setVariable` in class `Binding`
    Parameters:
      `name` - the name of the variable to set
      `value` - the new value for the given variable

  - ### getVariables

    public Map getVariables()
    Overrides:
      `getVariables` in class `Binding`

  - ### getVariable

    public Object getVariable​(String name)
    Overrides:
      `getVariable` in class `Binding`
    Parameters:
      `name` - the name of the variable to lookup
    Returns:
      a writer, an output stream, a markup builder or another requested object

  - ### forward

    public void forward​(String path) throws ServletException, IOException
    Throws:
      `ServletException`
      `IOException`

  - ### include

    public void include​(String path) throws ServletException, IOException
    Throws:
      `ServletException`
      `IOException`

  - ### redirect

    public void redirect​(String location) throws IOException
    Throws:
      `IOException`