NSIS script for java installation

Question

I want to install Java using an NSIS script, but i have to know whether Java is installed or not in the system (Windows). based on the register keys how can we check if Java

Answer 1

The following fragment of code checks if Java is installed (jre or jdk). If Java is not installed, it will install it. The script also saves the path to Java in a variable $JavaInstallationPath.

Var JavaInstallationPath
Section "Find Java" FINDJAVA    
    DetectTry1:
    StrCpy $1 "SOFTWARE\JavaSoft\Java Runtime Environment"  
    StrCpy $2 0  
    ReadRegStr $2 HKLM "$1" "CurrentVersion"  
    StrCmp $2 "" DetectTry2 JRE 
    JRE:
    ReadRegStr $5 HKLM "$1\$2" "JavaHome"  
    StrCmp $5 "" DetectTry2 GetValue    

    DetectTry2:  
    ReadRegStr $2 HKLM "SOFTWARE\JavaSoft\Java Development Kit" "CurrentVersion"  
    StrCmp $2 "" NoJava JDK 
    JDK:
    ReadRegStr $5 HKLM "SOFTWARE\JavaSoft\Java Development Kit\$2" "JavaHome"  
    StrCmp $5 "" NoJava GetValue

    GetValue:
    StrCpy $JavaInstallationPath $5
    Messagebox MB_OK "Javahome value: $JavaInstallationPath"
    Goto done

    NoJava:  
    Messagebox MB_OK "No Java installation detected. Installing Java."  
    # Install Java
    ExecWait "$INSTDIR\java\jre-6u26-windows-i586.exe"
    Goto DetectTry1

    done:   
    #$JavaInstallationPath should contain the system path to Java
SectionEnd  

I think you can also put the above code in a function and call it wherever you like in your NSIS script.