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POHow do I convert a string to and from JSON with escaped/special characters using DBXJSON?
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copied!<p>I'm having trouble converting a string with escaped characters <strong>to</strong> and <strong>from</strong> a TJsonString. (I'm using Delphi XE 2, Update 4, Hotfix 1).</p> <p>NOTE: I am familiar with the <a href="http://www.progdigy.com/?page_id=6" rel="nofollow noreferrer">SuperObject</a>, but my requirements are to use the DBXJSON unit.</p> <p>It looks like the TJSONString is not correctly escaped when returning the JSON representation via the ToString() method.</p> <p><strong>What (if anything) am I doing wrong and how do I correctly convert a string with special characters to/from its correct JSON representation?</strong></p> <p>Perhaps I missed something, but none of the following Q&As seemed to address this directly:</p> <ul> <li><a href="https://stackoverflow.com/questions/9713491/delphi-decode-json-utf8-escaped-text">Delphi decode json/utf8 escaped text</a></li> <li><a href="https://stackoverflow.com/questions/7731833/delphi-json-library-for-xe2-available-for-object-serialization">Delphi JSON library for XE2 available for object serialization</a></li> <li><a href="https://stackoverflow.com/questions/10549935/delphi-json-array">Delphi: JSON array</a></li> <li><a href="https://stackoverflow.com/questions/10808912/how-to-parse-nested-json-object-in-delphi-xe2">How to parse nested JSON object in Delphi XE2?</a></li> <li><a href="https://stackoverflow.com/questions/10559080/nested-json-object-deserializing-using-delphi-2012">Nested json object deserializing using Delphi 2012</a></li> </ul> <blockquote> <p><strong>EDIT:</strong></p> <p>As it turns out, the examples below were indeed working as expected.</p> <p>What wasn't clear to me was that when <strong>creating</strong> a TJSONString via it's constructor and adding it to a TJSONObject, the ToString() method will return an <strong>escaped</strong> representation. However, after <strong>parsing</strong> a TJSONObject, the ToString() method will returned the <strong>un-escaped</strong> representation.</p> <p>The only other caveat was that the EscapeString() function in the sample code below was handling the double-quote. Although I wasn't using the double quote here, some of my other code was, and that caused the parsing to fail because TJSONString already escapes that character. I've updated my sample code to remove this handling from the EscapeString() function, which is what I've been using in my own classes.</p> <p>Thanks again to @Linas for the answer, which helped me to "get" it.</p> </blockquote> <p><strong>Raw String Value:</strong></p> <pre><code>Text := 'c:\path\name' +#13 + #10 + 'Next Line'; Text: c:\path\name Next Line </code></pre> <p><strong>What DBXJSON produces (NO ESCAPES):</strong></p> <pre><code>JsonString: "c:\path\name Next Line" JsonPair: "MyString":"c:\path\name Next Line" JsonObject: {"MyString":"c:\path\name Next Line"} </code></pre> <p><strong>Parsing UN-escaped Text <em>FAILS</em>:</strong></p> <pre><code>Text to parse: {"MyString":"c:\path\name Next Line"} Parsed JsonObject = *NIL* </code></pre> <p><strong>What I <em>EXPECT</em> DBXJSON to produce:</strong></p> <pre><code>Escaped String: c:\\path\\name\r\nNext Line JsonString: "c:\\path\\name\r\nNext Line" JsonPair: "MyString":"c:\\path\\name\r\nNext Line" JsonObject: {"MyString":"c:\\path\\name\r\nNext Line"} </code></pre> <p><strong>Parsing ESCAPED Text (<em>INVALID</em>) (Text to parse validated with <a href="http://jsonlint.com/" rel="nofollow noreferrer">JSONLint</a>):</strong></p> <pre><code>Text to parse: {"MyString":"c:\\path\\name\r\nNext Line"} Parsed JsonObject.ToString(): {"MyString":"c:\path\name Next Line"} </code></pre> <p><strong><em>I've noticed that the only special character TJSONString seems to process correctly is the double quote (").</em></strong></p> <p>Here is the code I'm using:</p> <pre><code>program JsonTest; {$APPTYPE CONSOLE} {$R *.res} uses System.SysUtils, DbxJson; function EscapeString(const AValue: string): string; const ESCAPE = '\'; // QUOTATION_MARK = '"'; REVERSE_SOLIDUS = '\'; SOLIDUS = '/'; BACKSPACE = #8; FORM_FEED = #12; NEW_LINE = #10; CARRIAGE_RETURN = #13; HORIZONTAL_TAB = #9; var AChar: Char; begin Result := ''; for AChar in AValue do begin case AChar of // !! Double quote (") is handled by TJSONString // QUOTATION_MARK: Result := Result + ESCAPE + QUOTATION_MARK; REVERSE_SOLIDUS: Result := Result + ESCAPE + REVERSE_SOLIDUS; SOLIDUS: Result := Result + ESCAPE + SOLIDUS; BACKSPACE: Result := Result + ESCAPE + 'b'; FORM_FEED: Result := Result + ESCAPE + 'f'; NEW_LINE: Result := Result + ESCAPE + 'n'; CARRIAGE_RETURN: Result := Result + ESCAPE + 'r'; HORIZONTAL_TAB: Result := Result + ESCAPE + 't'; else begin if (Integer(AChar) < 32) or (Integer(AChar) > 126) then Result := Result + ESCAPE + 'u' + IntToHex(Integer(AChar), 4) else Result := Result + AChar; end; end; end; end; procedure Test; var Text: string; JsonString: TJsonString; JsonPair: TJsonPair; JsonObject: TJsonObject; begin try Writeln('Raw String Value'); Writeln('-----------------'); Text := 'c:\path\name' +#13 + #10 + 'Next Line'; Writeln('Text: ', Text); JsonString := TJsonString.Create(Text); JsonPair := TJsonPair.Create('MyString', JsonString); JsonObject := TJsonObject.Create(JsonPair); // DBXJSON results Writeln; Writeln('What DBXJSON produces'); Writeln('---------------------'); Writeln('JsonString: ', JsonString.ToString); Writeln; Writeln('JsonPair: ', JsonPair.ToString); Writeln; Writeln('JsonObject: ', JsonObject.ToString); Writeln; // assign JSON representation Text := JsonObject.ToString; // free json object JsonObject.Free; // parse it JsonObject:= TJsonObject.ParseJsonValue(TEncoding.ASCII.GetBytes( Text), 0) as TJsonObject; Writeln('Parsing UN-escaped Text *FAILS* '); Writeln('----------------------------------'); Writeln('Text to parse: ', Text); Writeln; if (JsonObject = nil) then Writeln('Parsed JsonObject = *NIL*') else Writeln('Parsed JsonObject: ', JsonObject.ToString); Writeln; // free json object JsonObject.Free; // expected results Text := 'c:\path\name' +#13 + #10 + 'Next Line'; Text := EscapeString(Text); JsonString := TJsonString.Create(Text); JsonPair := TJsonPair.Create('MyString', JsonString); JsonObject := TJsonObject.Create(JsonPair); Writeln('What I *EXPECT* DBXJSON to produce'); Writeln('----------------------------------'); Writeln('Escaped String: ', Text); Writeln; Writeln('JsonString: ', JsonString.ToString); Writeln; Writeln('JsonPair: ', JsonPair.ToString); Writeln; Writeln('JsonObject: ', JsonObject.ToString); Writeln; // assign JSON representation Text := JsonObject.ToString; // free json object JsonObject.Free; // parse it JsonObject:= TJsonObject.ParseJsonValue(TEncoding.ASCII.GetBytes( Text), 0) as TJsonObject; Writeln('Parsing ESCAPED Text (*INVALID*) '); Writeln('----------------------------------'); Writeln('Text to parse: ', Text); Writeln; Writeln('Parsed JsonObject.ToString(): ', JsonObject.ToString); Writeln; Readln; except on E: Exception do begin Writeln(E.ClassName, ': ', E.Message); Readln; end; end; end; begin Test; end. </code></pre>

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