Package: groovy.servlet

## [Java] Class ServletBinding

- groovy.servlet.ServletBinding

-     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 and description
    `ServletBinding(HttpServletRequest request, HttpServletResponse response, ServletContext context)` Initializes a servlet binding.

  - ### Methods Summary

    Methods
    Type Params | Return Type | Name and description
    --- | --- | ---
    `` | `public void` | `forward(String path)`
    `` | `public Object` | `getVariable(String name)` Returns: a writer, an output stream, a markup builder or another requested object
    `` | `public Map` | `getVariables()`
    `` | `public void` | `include(String path)`
    `` | `public void` | `redirect(String location)`
    `` | `public void` | `setVariable(String name, Object value)`

  - ### Inherited Methods Summary

    Inherited Methods
    Methods inherited from class | Name
    --- | ---
    `class Binding` | `getProperty, getVariable, getVariables, hasVariable, removeVariable, setProperty, setVariable`
    `class GroovyObjectSupport` | `getMetaClass, setMetaClass`

- - ### Constructor Detail

    - #### 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 Detail

    - #### public void forward(String path)

    - #### @Override
      public Object getVariable(String name)

      Returns:
        a writer, an output stream, a markup builder or another requested object

    - #### @Override
      public Map getVariables()

    - #### public void include(String path)

    - #### public void redirect(String location)

    - #### @Override
      public void setVariable(String name, Object value)