[spring-extensions] 02/05: Generic Spring expression predicate.

[Ian Young]

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commit 266400d88048ac4bc8eec03a1d28aaadbec3858f
Author: Scott Cantor <cantor.2 at osu.edu>
AuthorDate: Thu Apr 5 21:53:14 2018 -0400

    Generic Spring expression predicate.
---
 .../ext/spring/util/SpringExpressionPredicate.java | 131 +++++++++++++++++++++
 1 file changed, 131 insertions(+)

diff --git a/src/main/java/net/shibboleth/ext/spring/util/SpringExpressionPredicate.java b/src/main/java/net/shibboleth/ext/spring/util/SpringExpressionPredicate.java
new file mode 100644
index 0000000..769d97d
--- /dev/null
+++ b/src/main/java/net/shibboleth/ext/spring/util/SpringExpressionPredicate.java
@@ -0,0 +1,131 @@
+/*
+ * Licensed to the University Corporation for Advanced Internet Development,
+ * Inc. (UCAID) under one or more contributor license agreements.  See the
+ * NOTICE file distributed with this work for additional information regarding
+ * copyright ownership. The UCAID licenses this file to You under the Apache
+ * License, Version 2.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.shibboleth.ext.spring.util;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import net.shibboleth.utilities.java.support.annotation.ParameterName;
+import net.shibboleth.utilities.java.support.annotation.constraint.NotEmpty;
+import net.shibboleth.utilities.java.support.logic.Constraint;
+import net.shibboleth.utilities.java.support.primitive.StringSupport;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.EvaluationException;
+import org.springframework.expression.ExpressionParser;
+import org.springframework.expression.ParseException;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
+
+import com.google.common.base.Predicate;
+
+/**
+ * Predicate whose condition is defined by an Spring EL expression.
+ * 
+ * @param <T> type of input
+ * 
+ * @since 5.4.0
+ */
+public class SpringExpressionPredicate<T> implements Predicate<T> {
+    
+    /** Class logger. */
+    @Nonnull private final Logger log = LoggerFactory.getLogger(SpringExpressionPredicate.class);
+
+    /** SpEL expression to evaluate. */
+    @Nullable private String springExpression;
+    
+    /** A custom object to inject into the expression context. */
+    @Nullable private Object customObject;
+
+    /** Whether to raise runtime exceptions if expression fails. */
+    private boolean hideExceptions;
+    
+    /** Value to return from predicate when an error occurs. */
+    private boolean returnOnError;
+
+    /**
+     * Constructor.
+     *
+     * @param expression the expression to evaluate
+     */
+    public SpringExpressionPredicate(@Nonnull @NotEmpty @ParameterName(name="expression") final String expression) {
+        springExpression = Constraint.isNotNull(StringSupport.trimOrNull(expression),
+                "Expression cannot be null or empty");
+    }
+
+
+    /**
+     * Set a custom (externally provided) object.
+     * 
+     * @param object the custom object
+     */
+    public void setCustomObject(@Nullable final Object object) {
+        customObject = object;
+    }
+
+    /**
+     * Set whether to hide exceptions in expression execution (default is false).
+     * 
+     * @param flag flag to set
+     */
+    public void setHideExceptions(final boolean flag) {
+        hideExceptions = flag;
+    }
+
+    /**
+     * Set value to return if an error occurs (default is false).
+     * 
+     * @param flag flag to set
+     */
+    public void setReturnOnError(final boolean flag) {
+        returnOnError = flag;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean apply(@Nullable final T input) {
+
+        try {
+            final ExpressionParser parser = new SpelExpressionParser();
+            final StandardEvaluationContext context = new StandardEvaluationContext();
+            context.setVariable("custom", customObject);
+            context.setVariable("input", input);
+            prepareContext(context, input);
+            return parser.parseExpression(springExpression).getValue(context, Boolean.class);
+        } catch (final ParseException|EvaluationException e) {
+            log.error("Error evaluating Spring expression", e);
+            if (hideExceptions) {
+                return returnOnError;
+            }
+            throw e;
+        }
+    }
+    
+    /**
+     * Decorate the expression context with any additional content.
+     * 
+     * @param context expression context
+     * @param input to predicate
+     */
+    protected void prepareContext(@Nonnull final EvaluationContext context, @Nullable final T input) {
+        
+    }
+
+}
\ No newline at end of file

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