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This article is about the benefits of using the Properties class in JAVA. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Many developers complain that C++ can't bind Properties classes like Java does. Java's Properties class inherently contains a file that is used to read and write properties in the Properties class, which can be written as follows: = (for example: ConnectToInternet=Use IE).

The advantage of using Properties classes is that you can easily understand and modify them. In the first part of this article, you will see that we can also use the Properties class in C++. The second part of this article will show you that by using the operators > > and

# include string >

# include sstream >

# include map >

# include vector >

# include fstream >

# include algorithm >

# include functional >

/ / allow string conversion

Template

< class FromCharType, class ToCharType>

Inline std::basic_string

< ToCharType>

Convert_string (const std::basic_string

< FromCharType>

& strSource)

{

Std::basic_string

< ToCharType>

StrDest

Int nSourceLen = strSource.length ()

StrDest.resize (nSourceLen)

For (int idxChar = 0; idxChar)

< nSourceLen; idxChar++) { strDest[ idxChar] = ( ToCharType)strSource[ idxChar]; } return strDest; } // 用于trim_spaces; template< class CharType>

Struct is_char_in_str: public std::binary_function

< CharType, std::basic_string< CharType>

, bool >

{

Bool operator () (CharType ch, const std::basic_string

< CharType>

& strSource) const

{return (strSource.find (ch)! = std::basic_string

< CharType>

:: npos);}

}

/ / eliminate spaces in a string

Template

< class CharType>

Std::basic_string

< CharType>

Trim_spaces (const std::basic_string

< CharType>

& strSource)

{

Std::basic_string

< CharType>

StrSpaces; strSpaces + = (CharType)'; strSpaces + = (CharType)''

Typedef std::basic_string

< CharType>

String_type

String_type::const_iterator

ItFirst = std::find_if (strSource.begin (), strSource.end ()

Std::not1 (std::bind2nd (is_char_in_str)

< CharType>

(), strSpaces))

String_type::const_reverse_iterator

RitLast = std::find_if (strSource.rbegin (), strSource.rend ()

Std::not1 (std::bind2nd (is_char_in_str)

< CharType>

(), strSpaces))

String_type::const_iterator itLast = & * ritLast

If (itFirst

Class file_reader_writer

{

Typedef std::basic_string

< CharType>

String_type

Public:

/ /... Needed within the basic_properties!

Typedef CharType char_type

Public:

File_reader_writer (const char * strFileName)

M_bIsDirty (false), m_strFileName (strFileName) {read_properties ();}

~ file_reader_writer () {save ();}

Void save ()

{write_properties ();}

Bool has_property (const string_type & strPropertyName) const

{

PropertiesCollection::const_iterator itFound = m_collProperties.find (strPropertyName)

Return (itFound! = m_collProperties.end ())

}

Const string_type & get_property (const string_type & strPropertyName) const

{

PropertiesCollection::const_iterator itFound = m_collProperties.find (strPropertyName)

If (itFound! = m_collProperties.end ())

Return itFound- > second.m_strValue

Else

Throw properties_exception (

"Cound not get property value for'" + convert_string

< char_type, char>

(strPropertyName) +

"'since this property does not exist.")

}

Void set_property (const string_type & strProperty, const string_type & strPropertyValue)

{

PropertiesCollection::iterator itFound = m_collProperties.find (strProperty)

If (itFound = = m_collProperties.end ())

/ / it is a new property

M_aProperties.push_back (strProperty)

M_collProperties [strProperty] .m _ strValue = strPropertyValue

M_bIsDirty = true

}

Const string_type & get_property_comment (const string_type & strPropertyName) const

{

PropertiesCollection::const_iterator itFound = m_collProperties.find (strPropertyName)

If (itFound! = m_collProperties.end ())

Return itFound- > second.m_strComment

Else

Throw properties_exception (

"Cound not get property comment for'" + convert_string

< char_type, char>

(strPropertyName) +

"'since this property does not exist.")

}

Void set_property_comment (const string_type & strPropertyName, const string_type & strPropertyComment)

{

PropertiesCollection::iterator itFound = m_collProperties.find (strPropertyName)

If (itFound! = m_collProperties.end ())

ItFound- > second.m_strComment = strPropertyComment

Else

Throw properties_exception (

"Cound not set property comment for'" + convert_string

< char_type, char>

(strPropertyName) +

"'since this property does not exist.")

M_bIsDirty = true

}

Private:

Static const char_type get_delimeter () {return'=';}

Static const char_type get_comment () {return'#';}

Void read_properties ()

{

Const char DELIMETER = get_delimeter ()

Const char COMMENT = get_comment ()

Std::basic_ifstream

< char_type>

StreamIn (m_strFileName.c_str ())

String_type strLine

String_type strComment

While (std::getline (streamIn, strLine))

{

StrLine = trim_spaces (strLine)

Bool bIsComment = strLine.empty () | | (strLine [0] = = COMMENT)

If (bIsComment)

{strComment + = strLine; strComment + =';}

Else

{

Int idxDelimeter = strLine.find (DELIMETER)

If (idxDelimeter! = string_type::npos)

{

String_type strPropertyName = strLine.substr (0, idxDelimeter)

String_type strPropertyValue = strLine.substr (idxDelimeter + 1)

StrPropertyName = trim_spaces (strPropertyName)

StrPropertyValue = trim_spaces (strPropertyValue)

M_collProperties.insert (

Std::make_pair (strPropertyName, OneProperty (strPropertyValue, strComment)

M_aProperties.push_back (strPropertyName)

StrComment.erase ()

}

Else

Throw properties_exception (

"While reading from file'" + m_strFileName +

"', we encountered an invalid line:" + convert_string

< char_type, char>

(strLine))

}

}

M_strLastComment = strComment

}

Void write_properties () const

{

If (! m_bIsDirty)

/ / No need to save

; return

Const char DELIMETER = get_delimeter ()

Std::basic_ofstream

< char_type>

StreamOut (m_strFileName.c_str ())

PropertiesArray::const_iterator

ItFirst = m_aProperties.begin (), itLast = m_aProperties.end ()

While (itFirst! = itLast)

{

Const string_type & strPropertyName = * itFirst

Const OneProperty & property = m_collProperties.find (strPropertyName)-> second

Write_property_comment (streamOut, property.m_strComment)

String_type strToWrite = strPropertyName

StrToWrite + =''; strToWrite + = DELIMETER; strToWrite + =''

StreamOut strToWrite streamComment (strComment)

String_type strLine

While (std::getline (streamComment, strLine))

{

If (! strLine.empty ()

If (strLine [0] = = COMMENT)

StreamOut

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