Inno Setup, detect Java version

Question

When installing my Java app with Inno Setup, I would like the installer to check if Java 7 or above is present, and install it if needed. But apparently, my current code fails to detect Java 8 on the computer of some of my clients. I couldn't reproduce the bug, though. Do you see something that I could be missing? Maybe this code doesn't work with recent Windows?

Basically, I just check the registry for Java >= 1.7.

[Code]

function InitializeSetup(): Boolean;
var
 ErrorCode: Integer;
 JavaInstalled : Boolean;
 ResultMsg : Boolean;
 Versions: TArrayOfString;
 I: Integer;
 regRoot: Integer;
begin
 { Check which view of registry should be taken: }
 regRoot := HKLM
 begin
  if IsWin64 then
  begin
   regRoot := HKLM64
  end;
 end;
 if (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Runtime Environment', Versions)) or (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Development Kit', Versions)) then
 begin
  for I := 0 to GetArrayLength(Versions)-1 do
   if JavaInstalled = true then
   begin
    //do nothing
   end else
   begin
    if ( Versions[I][2]='.' ) and ( ( StrToInt(Versions[I][1]) > 1 ) or ( ( StrToInt(Versions[I][1]) = 1 ) and ( StrToInt(Versions[I][3]) >= 7 ) ) ) then
    begin
     JavaInstalled := true;
    end else
    begin
     JavaInstalled := false;
    end;
   end;
 end else
 begin
  JavaInstalled := false;
 end;

 if JavaInstalled then
 begin
  Result := true;
 end else
 begin
  ResultMsg := MsgBox(ExpandConstant('{cm:JavaRequired}'), mbConfirmation, MB_YESNO) = idYes;
  if ResultMsg = false then
  begin
   Result := false;
  end else
  begin
   Result := true;
   ShellExec('open', 'http://www.java.com/getjava/', '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
  end;
 end;
end;

Edit: This is the final result based on Martin's answer.

[Code]
function CutJavaVersionPart(var V: string): Integer;
var
  S: string;
  P: Integer;
begin
  if Length(V) = 0 then
  begin
    Result := 0;
  end
    else
  begin
    P := Pos('.', V);
    if P = 0 then P := Pos('_', V);

    if P > 0 then
    begin
      S := Copy(V, 1, P - 1);
      Delete(V, 1, P);
    end
      else
    begin
      S := V;
      V := '';
    end;
    Result := StrToIntDef(S, 0);
  end;
end;

function MaxJavaVersion(V1, V2: string): string;
var
  Part1, Part2: Integer;
  Buf1, Buf2: string;
begin
  Buf1 := V1;
  Buf2 := V2;
  Result := '';
  while (Result = '') and
        ((Buf1 <> '') or (Buf2 <> '')) do
  begin
    Part1 := CutJavaVersionPart(Buf1);
    Part2 := CutJavaVersionPart(Buf2);
    if Part1 > Part2 then Result := V1
      else
    if Part2 > Part1 then Result := V2;
  end;
end;

function GetJavaVersion(): string;
var
  TempFile: string;
  ResultCode: Integer;
  S: AnsiString;
  P: Integer;
begin
  TempFile := ExpandConstant('{tmp}\javaversion.txt');
  if (not ExecAsOriginalUser(
            ExpandConstant('{cmd}'), '/c java -version 2> "' + TempFile + '"', '',
            SW_HIDE, ewWaitUntilTerminated, ResultCode)) or
     (ResultCode <> 0) then
  begin
    Log('Failed to execute java -version');
  end
    else
  if not LoadStringFromFile(TempFile, S) then
  begin
    Log(Format('Error reading file %s', [TempFile]));
  end
    else
  if Copy(S, 1, 14) <> 'java version "' then
  begin
    Log('Output of the java -version not as expected');
  end
    else
  begin
    Delete(S, 1, 14);
    P := Pos('"', S);
    if P = 0 then
    begin
      Log('Output of the java -version not as expected');
    end
      else
    begin
      SetLength(S, P - 1);
      Result := S;
    end;
  end;

  DeleteFile(TempFile);
end;

function HasJava1Dot7OrNewer: Boolean;
begin
  Result := (MaxJavaVersion('1.6.9', GetJavaVersion) <> '1.6.9');
end;

function InitializeSetup(): Boolean;
var
  ErrorCode: Integer;
begin
  Result := HasJava1Dot7OrNewer;
  if not Result then
  begin
    Result := MsgBox(ExpandConstant('{cm:JavaRequired}'), mbConfirmation, MB_YESNO) = idYes;
    if Result then
    begin
      ShellExec(
        'open', 'https://www.java.com/getjava/', '', '', SW_SHOWNORMAL, ewNoWait, ErrorCode);
    end;
  end;
end;

Answer 1

I do not have the JavaSoft key in HKLM\Software. I have it in HKLM\SOFTWARE\WOW6432Node. What is actually the HKLM\SOFTWARE in Inno Setup (being 32-bit application).

So it looks like you just need to remove the if IsWin64 then regRoot := HKLM64 block to make it working. Or try both options.

function CutJavaVersionPart(var V: string): Integer;
var
  S: string;
  P: Integer;
begin
  if Length(V) = 0 then
  begin
    Result := 0;
  end
    else
  begin
    P := Pos('.', V);
    if P = 0 then P := Pos('_', V);

    if P > 0 then
    begin
      S := Copy(V, 1, P - 1);
      Delete(V, 1, P);
    end
      else
    begin
      S := V;
      V := '';
    end;
    Result := StrToIntDef(S, 0);
  end;
end;

function MaxJavaVersion(V1, V2: string): string;
var
  Part1, Part2: Integer;
  Buf1, Buf2: string;
begin
  Buf1 := V1;
  Buf2 := V2;
  Result := '';
  while (Result = '') and
        ((Buf1 <> '') or (Buf2 <> '')) do
  begin
    Part1 := CutJavaVersionPart(Buf1);
    Part2 := CutJavaVersionPart(Buf2);
    if Part1 > Part2 then Result := V1
      else
    if Part2 > Part1 then Result := V2;
  end;
end;

function GetJavaVersionFromSubKey(RootKey: Integer; SubKeyName: string): string;
var
  Versions: TArrayOfString;
  I: Integer;
begin
  if RegGetSubkeyNames(RootKey, SubKeyName, Versions) then
  begin
    for I := 0 to GetArrayLength(Versions) - 1 do
    begin
      Result := MaxJavaVersion(Result, Versions[I]);
    end;
  end;
end;

function GetJavaVersionFromRootKey(RootKey: Integer): string;
begin
  Result := 
    MaxJavaVersion(
      GetJavaVersionFromSubKey(RootKey, 'SOFTWARE\JavaSoft\Java Runtime Environment'),
      GetJavaVersionFromSubKey(RootKey, 'SOFTWARE\JavaSoft\Java Development Kit'));
end;

function GetJavaVersion: string;
begin
  Result := GetJavaVersionFromRootKey(HKLM);
  if IsWin64 then
  begin
    Result := MaxJavaVersion(Result, GetJavaVersionFromRootKey(HKLM64));
  end;
end;

For your specific needs, you can check, if Java 1.7 or newer is installed like this:

function HasJava1Dot7OrNewer: Boolean;
begin
  Result := (MaxJavaVersion('1.6.9', GetJavaVersion) <> '1.6.9');
end;

---

Or did you consider running java -version instead?

function GetJavaVersion2: string;
var
  TempFile: string;
  ResultCode: Integer;
  S: AnsiString;
  P: Integer;
begin
  TempFile := ExpandConstant('{tmp}\javaversion.txt');
  if (not ExecAsOriginalUser(
            ExpandConstant('{cmd}'), '/c java -version 2> "' + TempFile + '"', '',
            SW_HIDE, ewWaitUntilTerminated, ResultCode)) or
     (ResultCode <> 0) then
  begin
    Log('Failed to execute java -version');
  end
    else
  if not LoadStringFromFile(TempFile, S) then
  begin
    Log(Format('Error reading file %s', [TempFile]));
  end
    else
  if Copy(S, 1, 14) <> 'java version "' then
  begin
    Log('Output of the java -version not as expected');
  end
    else
  begin
    Delete(S, 1, 14);
    P := Pos('"', S);
    if P = 0 then
    begin
      Log('Output of the java -version not as expected');
    end
      else
    begin
      SetLength(S, P - 1);
      Result := S;
    end;
  end;

  DeleteFile(TempFile);
end;

---

A bit more efficient implementation of the InitializeSetup:

function InitializeSetup(): Boolean;
var
  ErrorCode: Integer;
begin
  Result := HasJava1Dot7OrNewer;
  if not Result then
  begin
    Result := MsgBox(ExpandConstant('{cm:JavaRequired}'), mbConfirmation, MB_YESNO) = idYes;
    if Result then
    begin
      ShellExec(
        'open', 'https://www.java.com/getjava/', '', '', SW_SHOWNORMAL, ewNoWait, ErrorCode);
    end;
  end;
end;

Answer 2

Answering my own comment, here's my variation which should work regardless of whether the installed JRE is Oracle's or OpenJDK's, and for Java versions prior to and after Java 9.

The GetJavaMajorVersion() function returns the Java version as an integer. For versions where java -version reports "1.x.*" (up to and including Java 8) it will return x, otherwise (Java 9 and later) it will return the actual major number. If for some reason the call to java -version fails it will return 0.

function GetJavaMajorVersion(): integer;
var
  TempFile: string;
  ResultCode: Integer;
  S: AnsiString;
  P: Integer;
begin
  Result := 0;

  { execute java -version and redirect output to a temp file }
  TempFile := ExpandConstant('{tmp}\javaversion.txt');
  if (not ExecAsOriginalUser(ExpandConstant('{cmd}'), '/c java -version 2> "' + TempFile + '"', '',SW_HIDE, ewWaitUntilTerminated, ResultCode)) 
    or (ResultCode <> 0) then
  begin
    Log('Failed to execute java -version');
    exit;
  end;

  { read file into variable S }
  LoadStringFromFile(TempFile, S)
  DeleteFile(TempFile);
  Log(Format('java -version output: ' + #13#10 + '%s', [S]));

  { extract version (between quotes) }
  P := Pos('"', S);
  Delete(S, 1, P);
  P := Pos('"', S);
  SetLength(S, P - 1);
  Log(Format('Extracted version: %s', [S]));

  { extract major }
  if Copy(S, 1, 2) = '1.' then
  begin
    Delete(S, 1, 2)
  end;
  P := Pos('.', S);
  SetLength(S, P - 1);
  Log(Format('Major version: %s', [S]));

  Result := StrToIntDef(S, 0);
end;

function InitializeSetup(): boolean;
var
  ResultCode: Integer;
begin
  if GetJavaMajorVersion >= 8 then
  begin
    Result := true;    
    exit;
  end;

  if MsgBox('This tool requires a Java Runtime Environment version 1.8 or newer to run. ' +
    'Please download and install the JRE and run this setup again. ' +
    'Would you like to open the JRE download page now?', mbCriticalError, MB_YESNO) = idYes then 
  begin
    Result := false;
    ShellExec('open', 'https://java.com/download/', '', '', SW_SHOWNORMAL, ewNoWait, ResultCode);
  end;  
end;

Lots of room for improvement, but it does the job.