diff -r 61669abf277f -r e8eecee6aadf src/main/kotlin/de/uapcore/lightpit/AbstractServlet.kt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/kotlin/de/uapcore/lightpit/AbstractServlet.kt	Fri Apr 02 11:59:14 2021 +0200
@@ -0,0 +1,182 @@
+/*
+ * Copyright 2021 Mike Becker. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package de.uapcore.lightpit
+
+import de.uapcore.lightpit.DataSourceProvider.Companion.SC_ATTR_NAME
+import de.uapcore.lightpit.dao.DataAccessObject
+import de.uapcore.lightpit.dao.createDataAccessObject
+import java.sql.SQLException
+import java.util.*
+import javax.servlet.http.HttpServlet
+import javax.servlet.http.HttpServletRequest
+import javax.servlet.http.HttpServletResponse
+
+abstract class AbstractServlet : LoggingTrait, HttpServlet() {
+
+    /**
+     * Contains the GET request mappings.
+     */
+    private val getMappings = mutableMapOf<PathPattern, MappingMethod>()
+
+    /**
+     * Contains the POST request mappings.
+     */
+    private val postMappings = mutableMapOf<PathPattern, MappingMethod>()
+
+    protected fun get(pattern: String, method: MappingMethod) {
+        getMappings[PathPattern(pattern)] = method
+    }
+
+    protected fun post(pattern: String, method: MappingMethod) {
+        postMappings[PathPattern(pattern)] = method
+    }
+
+    private fun notFound(http: HttpRequest, dao: DataAccessObject) {
+        http.response.sendError(HttpServletResponse.SC_NOT_FOUND)
+    }
+
+    private fun findMapping(
+        mappings: Map<PathPattern, MappingMethod>,
+        req: HttpServletRequest
+    ): Pair<PathPattern, MappingMethod> {
+        val requestPath = sanitizedRequestPath(req)
+        val candidates = mappings.filter { it.key.matches(requestPath) }
+        return if (candidates.isEmpty()) {
+            Pair(PathPattern(requestPath), ::notFound)
+        } else {
+            if (candidates.size > 1) {
+                logger().warn("Ambiguous mapping for request path '{}'", requestPath)
+            }
+            candidates.entries.first().toPair()
+        }
+    }
+
+    private fun invokeMapping(
+        mapping: Pair<PathPattern, MappingMethod>,
+        req: HttpServletRequest,
+        resp: HttpServletResponse,
+        dao: DataAccessObject
+    ) {
+        val params = mapping.first.obtainPathParameters(sanitizedRequestPath(req))
+        val method = mapping.second
+        logger().trace("invoke {}", method)
+        method(HttpRequest(req, resp, params), dao)
+    }
+
+    private fun sanitizedRequestPath(req: HttpServletRequest) = req.pathInfo ?: "/"
+
+    private fun doProcess(
+        req: HttpServletRequest,
+        resp: HttpServletResponse,
+        mappings: Map<PathPattern, MappingMethod>
+    ) {
+        val session = req.session
+
+        // the very first thing to do is to force UTF-8
+        req.characterEncoding = "UTF-8"
+
+        // choose the requested language as session language (if available) or fall back to english, otherwise
+        if (session.getAttribute(Constants.SESSION_ATTR_LANGUAGE) == null) {
+            val availableLanguages = availableLanguages()
+            val reqLocale = req.locale
+            val sessionLocale = if (availableLanguages.contains(reqLocale)) reqLocale else availableLanguages.first()
+            session.setAttribute(Constants.SESSION_ATTR_LANGUAGE, sessionLocale)
+            logger().debug(
+                "Setting language for new session {}: {}", session.id, sessionLocale.displayLanguage
+            )
+        } else {
+            val sessionLocale = session.getAttribute(Constants.SESSION_ATTR_LANGUAGE) as Locale
+            resp.locale = sessionLocale
+            logger().trace("Continuing session {} with language {}", session.id, sessionLocale)
+        }
+
+        // set some internal request attributes
+        val http = HttpRequest(req, resp)
+        val fullPath = req.servletPath + Optional.ofNullable(req.pathInfo).orElse("")
+        req.setAttribute(Constants.REQ_ATTR_BASE_HREF, http.baseHref)
+        req.setAttribute(Constants.REQ_ATTR_PATH, fullPath)
+        req.getHeader("Referer")?.let {
+            // TODO: add a sanity check to avoid link injection
+            req.setAttribute(Constants.REQ_ATTR_REFERER, it)
+        }
+
+        // if this is an error path, bypass the normal flow
+        if (fullPath.startsWith("/error/")) {
+            http.styleSheets = listOf("error")
+            http.render("error")
+            return
+        }
+
+        // obtain a connection and create the data access objects
+        val dsp = req.servletContext.getAttribute(SC_ATTR_NAME) as DataSourceProvider
+        val dialect = dsp.dialect
+        val ds = dsp.dataSource
+        if (ds == null) {
+            resp.sendError(
+                HttpServletResponse.SC_SERVICE_UNAVAILABLE,
+                "JNDI DataSource lookup failed. See log for details."
+            )
+            return
+        }
+        try {
+            ds.connection.use { connection ->
+                val dao = createDataAccessObject(dialect, connection)
+                try {
+                    connection.autoCommit = false
+                    invokeMapping(findMapping(mappings, req), req, resp, dao)
+                    connection.commit()
+                } catch (ex: SQLException) {
+                    logger().warn("Database transaction failed (Code {}): {}", ex.errorCode, ex.message)
+                    logger().debug("Details: ", ex)
+                    resp.sendError(
+                        HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
+                        "Unhandled Transaction Error - Code: " + ex.errorCode
+                    )
+                    connection.rollback()
+                }
+            }
+        } catch (ex: SQLException) {
+            logger().error("Severe Database Exception (Code {}): {}", ex.errorCode, ex.message)
+            logger().debug("Details: ", ex)
+            resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Database Error - Code: " + ex.errorCode)
+        }
+    }
+
+    override fun doGet(req: HttpServletRequest, resp: HttpServletResponse) {
+        doProcess(req, resp, getMappings)
+    }
+
+    override fun doPost(req: HttpServletRequest, resp: HttpServletResponse) {
+        doProcess(req, resp, postMappings)
+    }
+
+    protected fun availableLanguages(): List<Locale> {
+        val langTags = servletContext.getInitParameter(Constants.CTX_ATTR_LANGUAGES)?.split(",")?.map(String::trim) ?: emptyList()
+        val locales = langTags.map(Locale::forLanguageTag).filter { it.language.isNotEmpty() }
+        return if (locales.isEmpty()) listOf(Locale.ENGLISH) else locales
+    }
+
+}