SAX XML インターフェイスの使用

{import * from CURL.XML.SAX.PARSER}

{define-class public MySAXApp {inherits DefaultHandler}

  field private output:VBox
  field private nesting-depth:int

  {constructor public {default parse-output:VBox}
    set self.output = parse-output
    {construct-super}
  }

  {method public {start-document}:void
    set self.nesting-depth = 0
    {self.output.add
        {text color="purple", Start document}
    }
  }

  {method public {end-document}:void
    {self.output.add
        {text color="purple",End document}
    }
  }

  {method public {start-element
                     uri:String,
                     name:String,
                     qname:String,
                     atts:Attributes
                 }:void
    set self.nesting-depth = self.nesting-depth + 1
    {self.output.add
        {HBox
            {Fill width = self.nesting-depth * 0.5in},
            {text color="navy", Start element: },
            {text color="fuchsia",
                {if uri != "" then
                    "[" & uri & "]"
                 else
                    ""
                }
            },
            {text color="fuchsia", {value name}}
        }
    }
  }

  {method public {end-element
                     uri:String,
                     name:String,
                     qname:String
                 }:void
    {self.output.add
        {HBox
            {Fill width = self.nesting-depth * 0.5in},
            {text color="navy", End element: },
            {text color="fuchsia",
                {if uri != "" then
                    "[" & uri & "]"
                 else
                    ""
                }
            },
            {text color="fuchsia", {value name}}
        }
    }
    set self.nesting-depth = self.nesting-depth - 1
  }
  
  {method public {characters
                     ch:StringBuf,
                     start:int,
                     length:int
                 }:void
    {self.output.add
        {HBox
            {Fill width = self.nesting-depth * 0.5in},
            {text color="teal", Characters: },
            {text color="lime", {ch.substr start, length}}
        }
    }
  }
  
  {method public {error exception:SAXParseException}:void
    {throw exception}
  }
  
  {method public {fatal-error exception:SAXParseException}:void
    {throw exception}
  }
  
  {method public {warning exception:SAXParseException}:void
    {throw exception}
  }
  
}

{define-proc {error-message parse-exception:SAXParseException}:String
    let sb:StringBuf={StringBuf "Error detected"}
    {if {parse-exception.get-line-number} != 0
     then
        {sb.concat " at line " & {parse-exception.get-line-number}}
        {if {parse-exception.get-system-id} != null
         then
            {sb.concat " of " & {parse-exception.get-system-id}}
        }
    }
    {sb.concat ": " & {parse-exception.get-message}}
    {return {sb.to-String}}
}

{let xr:XMLReader = {SAXParser}}
{let parse-output:VBox = {VBox}}
{let handler:MySAXApp = {MySAXApp parse-output}}
{xr.set-content-handler handler}
{xr.set-error-handler handler}

{define-proc {parse-and-display input-name:Url}:void
    || clear the parse output of any previous xml file
    {parse-output.clear}

    {try
        || Parse from what is found by opening input-name
        {xr.parse {InputSource system-id = input-name.name}}

     catch file-exception:IOException do
        || Handle any exception thrown due to the file read
        {parse-output.add
            {text color="red",
                A problem occurred while reading the file:
                {value file-exception}
            }
        }
     catch parse-exception:SAXParseException do
        || Handle any exception thrown while parsing the XML
        {parse-output.add
            {text color="red",
                A problem occurred parsing the XML file:
                {error-message parse-exception}
            }
        }
    }
}

{let command:CommandButton =
    {CommandButton
        label = "Choose File",
        {on Action do
            let f:#Url = {choose-location
                             title="Select an XML file to parse"
                         }
            {if-non-null f then
                {parse-and-display f}
             else
                {parse-output.clear}
                {parse-output.add
                    {text color="red",
                        Please select a file to parse.
                    }
                }
            }
        }
    }
}
|| Determine the location of the example XML file.
{let example-url:Url = {url "../../default/support/brillig.xml"}}

{VBox
    {heading XML Example},
    {text Select an XML file to be read. Hint: try
        {bold {value example-url.local-filename}}
    },
    command,
    {hrule},
    {ScrollBox height=4.5in, parse-output}
}