Detect Java version in Inno Setup

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;