From bee5dd259a4438d45ecd1bcc26dfba12875236d6 Mon Sep 17 00:00:00 2001
From: Thomas Lenz <thomas.lenz@egiz.gv.at>
Date: Tue, 26 Jun 2018 11:03:48 +0200
Subject: initial commit

---
 .../springweb/SpringWebExpressionEvaluator.java    | 145 +++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 eaaf_core/src/main/java/at/gv/egiz/eaaf/core/impl/idp/process/springweb/SpringWebExpressionEvaluator.java

(limited to 'eaaf_core/src/main/java/at/gv/egiz/eaaf/core/impl/idp/process/springweb/SpringWebExpressionEvaluator.java')

diff --git a/eaaf_core/src/main/java/at/gv/egiz/eaaf/core/impl/idp/process/springweb/SpringWebExpressionEvaluator.java b/eaaf_core/src/main/java/at/gv/egiz/eaaf/core/impl/idp/process/springweb/SpringWebExpressionEvaluator.java
new file mode 100644
index 00000000..229735e3
--- /dev/null
+++ b/eaaf_core/src/main/java/at/gv/egiz/eaaf/core/impl/idp/process/springweb/SpringWebExpressionEvaluator.java
@@ -0,0 +1,145 @@
+/*******************************************************************************
+ *******************************************************************************/
+package at.gv.egiz.eaaf.core.impl.idp.process.springweb;
+
+import java.io.Serializable;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+
+import javax.annotation.PostConstruct;
+import javax.servlet.http.HttpServletRequest;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.commons.lang3.BooleanUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.expression.BeanFactoryResolver;
+import org.springframework.expression.Expression;
+import org.springframework.expression.ExpressionParser;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
+
+import at.gv.egiz.eaaf.core.api.idp.process.ExecutionContext;
+import at.gv.egiz.eaaf.core.api.idp.process.ExpressionEvaluationContext;
+import at.gv.egiz.eaaf.core.api.idp.process.ExpressionEvaluator;
+import at.gv.egiz.eaaf.core.impl.idp.process.model.Transition;
+
+/**
+ * Expression evaluator for processing {@link Transition} conditions allowing to
+ * <ul>
+ * <li>reference Spring beans from the application context using {@code @myBeanName...},</li>
+ * <li>{@link ExecutionContext} properties using {@code ctx['property']},</li>
+ * <li>Multi valued {@link HttpServletRequest} parameters using {@code requestParameters['foo']} (keep in mind that this
+ * expression returns an array of String values) and</li>
+ * <li>Single valued {@link HttpServletRequest} parameters using {@code requestParameter['foo']}</li>
+ * </ul>
+ * 
+ * @author tknall
+ * 
+ */
+public class SpringWebExpressionEvaluator implements ExpressionEvaluator {
+
+	private Logger log = LoggerFactory.getLogger(getClass());
+	private ExpressionParser parser = new SpelExpressionParser();
+	private StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
+
+	@Autowired(required = false)
+	private ApplicationContext ctx;
+
+	@Autowired(required = false)
+	private HttpServletRequest request;
+
+	@PostConstruct
+	private void init() {
+		if (ctx != null) {
+			evaluationContext.setBeanResolver(new BeanFactoryResolver(ctx));
+		}
+	}
+
+	/**
+	 * Evaluation context that provides access to {@link HttpServletRequest} parameters using
+	 * {@code requestParameter['foo']} for single value parameters or {@code requestParameters['foo']} for multi value
+	 * parameters. Basic calls to {@code ctx} will be delegated.
+	 * 
+	 * @author tknall
+	 * 
+	 */
+	private class SpringWebExpressionEvaluationContext implements ExpressionEvaluationContext {
+
+		private static final long serialVersionUID = 1L;
+
+		/**
+		 * Creates a new expression evaluation context, providing access to HttpServletRequest parameter(s).
+		 * 
+		 * @param delegate
+		 *            The original {@link ExpressionEvaluationContext} to be delegated to for {@code ctx['foo']}
+		 *            expressions.
+		 */
+		public SpringWebExpressionEvaluationContext(ExpressionEvaluationContext delegate) {
+			this.delegate = delegate;
+		}
+
+		private ExpressionEvaluationContext delegate;
+
+		@Override
+		public Map<String, Serializable> getCtx() {
+			return delegate.getCtx();
+		}
+
+		@SuppressWarnings("unused")
+		public Map<String, String> getRequestParameter() {
+			if (request != null) {
+				Map<String, String> singleValueMap = new HashMap<String, String>();
+				Iterator<Entry<String, String[]>> it = request.getParameterMap().entrySet().iterator();
+				while (it.hasNext()) {
+					Entry<String, String[]> entry = it.next();
+					if (ArrayUtils.isNotEmpty(entry.getValue())) {
+						singleValueMap.put(entry.getKey(), entry.getValue()[0]);
+					}
+				}
+				return singleValueMap;
+			} else {
+				return Collections.<String, String> emptyMap();
+			}
+		}
+
+		@SuppressWarnings("unused")
+		public Map<String, String[]> getRequestParameters() {
+			if (request != null) {
+				return request.getParameterMap();
+			} else {
+				return Collections.<String, String[]> emptyMap();
+			}
+		}
+
+	}
+
+	@Override
+	public boolean evaluate(ExpressionEvaluationContext expressionContext, String expression) {
+		Objects.requireNonNull(expression, "Expression must not be null.");
+		log.trace("Evaluating '{}'.", expression);
+
+		Expression expr = parser.parseExpression(expression);
+		Boolean result = null;
+		try {
+			result = expr.getValue(evaluationContext, new SpringWebExpressionEvaluationContext(expressionContext),
+					Boolean.class);
+			if (result == null) {
+				log.warn("Evaluation of '{}' results in null-value.", expression);
+			} else {
+				log.debug("Expression '{}' -> {}", expression, result);
+			}
+		} catch (Exception e) {
+			log.warn("Expression '{}' could not be processed.", expression, e);
+		}
+
+		return BooleanUtils.isTrue(result);
+	}
+
+}
-- 
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