Java Runtime Check Task

JavaRuntimeCheckTask.cs

namespace Somewhere
{
    using System;
    using System.IO;
    using Microsoft.Win32;

    internal sealed class JavaRuntimeCheckTask
    {
        public void Verify(PackageContext context)
        {
            var layer = new JavaRuntimeLayer();

            // NOTE: this only works on Windows
            var localMachineRegistry = Registry.LocalMachine;
            if (SearchRegistry(layer, RegistryView.Registry64))
            {
                // found x64 JRE
            }
            else if (SearchRegistry(layer, RegistryView.Registry32))
            {
                // found x86 JRE
            }
            else
            {
                // found no JRE
            }

            int errors = 0;
            if (layer.Error != null)
            {
                if (this.FailPolicy == PackageManifestInstallTaskFailPolicy.Terminate || this.FailPolicy == PackageManifestInstallTaskFailPolicy.Ask)
                {
                    errors++;
                    interactor.WriteTaskError(this, layer.Error);
                }
                else
                {
                    interactor.WriteTaskInfo(this, layer.Error);
                }
            }
            else
            {
                interactor.WriteTaskInfo(this, "Found Java " + layer.JavaVersion + " installed at \"" + layer.JavaHome + "\". ");
            }

            context.Verified(this, errors == 0);
        }

        private static bool SearchRegistry(JavaRuntimeLayer layer, RegistryView mode)
        {
            layer.Clear();

            var localMachineRegistry = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, mode);
            layer.Is64Bit = mode == RegistryView.Registry64;
            layer.Is32Bit = mode == RegistryView.Registry32;

            if (localMachineRegistry != null)
            {
                var jreKey = localMachineRegistry.OpenSubKey("SOFTWARE\\JavaSoft\\Java Runtime Environment");
                if (jreKey != null)
                {
                    var jreVersionValue = jreKey.GetValue("CurrentVersion");
                    if (jreVersionValue != null)
                    {
                        layer.JavaVersion = jreVersionValue.ToString();

                        var jreCurrentKey = jreKey.OpenSubKey(layer.JavaVersion);
                        if (jreCurrentKey != null)
                        {
                            var jrePath = jreCurrentKey.GetValue("JavaHome");
                            if (jrePath != null)
                            {
                                layer.JavaHome = jrePath.ToString();

                                var javaExePath = Path.Combine(layer.JavaHome, "bin", "java.exe");
                                if (File.Exists(javaExePath))
                                {
                                    // ok!
                                }
                                else
                                {
                                    layer.Error = "No java executable in java home \"" + layer.JavaHome + "\". ";
                                }
                            }
                            else
                            {
                                layer.Error = "Java " + layer.JavaVersion + " looks to be installed but it is not (no JavaHome registry key). ";
                            }
                        }
                        else
                        {
                            layer.Error = "Java " + layer.JavaVersion + " looks to be installed but it is not (no version registry key). ";
                        }
                    }
                    else
                    {
                        layer.Error = "No Java JRE looks to be installed (even with a few registry keys present). ";
                    }
                }
                else
                {
                    layer.Error = "No Java JRE looks to be installed. ";
                }
            }
            else
            {
                layer.Error = "Windows Registry is not available. ";
            }

            return layer.Error == null;
        }
    }

    internal sealed class JavaRuntimeLayer
    {
        public JavaRuntimeLayer()
        {
        }

        public string Error { get; internal set; }

        public string JavaVersion { get; internal set; }

        public string JavaHome { get; internal set; }

        public bool Is64Bit { get; internal set; }

        public bool Is32Bit { get; internal set; }

        internal void Clear()
        {
            this.Error = null;
            this.JavaVersion = null;
            this.JavaHome = null;
            this.Is32Bit = this.Is64Bit = false;
        }
    }
}