Check Java is present before installing

Question

I'm creating an InnoSetup installer for a jar app. What I want to do right now is to check if java is present before proceeding with the install. So I only need to be sure the users will be able to run:

java -jar my-app.jar

What I'm doing right now is:

[Code]

function InitializeSetup(): Boolean;
var
  ErrorCode: Integer;
  JavaInstalled : Boolean;
  Result1 : Boolean;
begin
  JavaInstalled := RegKeyExists(HKLM,'SOFTWARE\JavaSoft\Java Runtime Environment\1.6');
  if JavaInstalled then
  begin
    Result := true;
  end else
    begin
      Result1 := MsgBox('This tool requires Java Runtime Environment version 1.6 or newer to run. Please download and install the JRE and run this setup again. Do you want to download it now?',
        mbConfirmation, MB_YESNO) = idYes;
      if Result1 = false then
      begin
        Result:=false;
      end else
      begin
        Result:=false;
        ShellExec('open',
          'http://javadl.sun.com/webapps/download/AutoDL?BundleId=33787',
          '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
      end;
    end;
  end;
end;

My questions are:

• Is checking the registry enough to be sure java's home dir will be in the PATH? (to be able to run "java" in the console)

• If a higher version of java is installed, will that key in the registry exist anyway or I will have to check for each higher version possible?

• Does anyone have a better way to download java than just showing a popup and taking the users to the download page?

Answer 1

For your third question, see here, under the Trademark and Licensing section. Exec summary: you can distribute the JRE along with your app. I think a few apps do this to ensure they do not have version compatibility issues - i.e install the JRE in a subfolder of the app itself.

As far as being in the PATH, why is that important? You can create a shortcut that refers to java.exe by its full path to run your app. Is it important that the user start the program via the command line themselves?

Answer 2

Instead of checking for a specific version, you can use

function RegKeyExists(const RootKey: Integer; const SubKeyName: String): Boolean;

to get the subkeys of HKLM\SOFTWARE\JavaSoft\Java Runtime Environment. (Is parallel installation of different versions possible? Don't know...) You would need to do some string fiddling to check if 1.6 or higher is installed, but it would be more flexible than checking for a specific version number.

Answer 3

I hope someone finds this useful, what I did is reusing some piece of the code placed in inno setups wiki to make a < > comparison with the version as a number:

; Both DecodeVersion and CompareVersion functions where taken from the  wiki
procedure DecodeVersion (verstr: String; var verint: array of Integer);
var
  i,p: Integer; s: string;
begin
  // initialize array
  verint := [0,0,0,0];
  i := 0;
  while ((Length(verstr) > 0) and (i < 4)) do
  begin
    p := pos ('.', verstr);
    if p > 0 then
    begin
      if p = 1 then s:= '0' else s:= Copy (verstr, 1, p - 1);
      verint[i] := StrToInt(s);
      i := i + 1;
      verstr := Copy (verstr, p+1, Length(verstr));
    end
    else
    begin
      verint[i] := StrToInt (verstr);
      verstr := '';
    end;
  end;

end;

function CompareVersion (ver1, ver2: String) : Integer;
var
  verint1, verint2: array of Integer;
  i: integer;
begin

  SetArrayLength (verint1, 4);
  DecodeVersion (ver1, verint1);

  SetArrayLength (verint2, 4);
  DecodeVersion (ver2, verint2);

  Result := 0; i := 0;
  while ((Result = 0) and ( i < 4 )) do
  begin
    if verint1[i] > verint2[i] then
      Result := 1
    else
      if verint1[i] < verint2[i] then
        Result := -1
      else
        Result := 0;
    i := i + 1;
  end;

end;

; Here's my code
function InitializeSetup(): Boolean;
var
  ErrorCode: Integer;
  JavaVer : String;
  Result1 : Boolean;
begin
    RegQueryStringValue(HKLM, 'SOFTWARE\JavaSoft\Java Runtime Environment', 'CurrentVersion', JavaVer);
    Result := false;
    if Length( JavaVer ) > 0 then
    begin
     if CompareVersion(JavaVer,'1.6') >= 0 then
     begin
      Result := true;
     end;
    end;
    if Result = false then
    begin
     Result1 := MsgBox('This tool requires Java Runtime Environment v1.6 or older to run. Please download and install JRE and run this setup again.' + #13 + #10 + 'Do you want to download it now?',
       mbConfirmation, MB_YESNO) = idYes;
     if Result1 = true then
     begin
      ShellExec('open',
        'http://www.java.com/en/download/manual.jsp#win',
        '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
     end;
    end;
end;

Thanks all for your help

Answer 4

I changed your code a little, I think this way newer versions of Java will be supported ;-)

function InitializeSetup(): Boolean;
var
 ErrorCode: Integer;
 JavaInstalled : Boolean;
 Result1 : Boolean;
 Versions: TArrayOfString;
 I: Integer;
begin
 if RegGetSubkeyNames(HKLM, 'SOFTWARE\JavaSoft\Java Runtime Environment', 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]) >= 6 ) ) ) then
    begin
     JavaInstalled := true;
    end else
    begin
     JavaInstalled := false;
    end;
   end;
 end else
 begin
  JavaInstalled := false;
 end;


 //JavaInstalled := RegKeyExists(HKLM,'SOFTWARE\JavaSoft\Java Runtime Environment\1.9');
 if JavaInstalled then
 begin
  Result := true;
 end else
    begin
  Result1 := MsgBox('This tool requires Java Runtime Environment version 1.6 or newer to run. Please download and install the JRE and run this setup again. Do you want to download it now?',
   mbConfirmation, MB_YESNO) = idYes;
  if Result1 = false then
  begin
   Result:=false;
  end else
  begin
   Result:=false;
   ShellExec('open',
    'http://www.java.com/getjava/',
    '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
  end;
    end;
end;


end.