1 files changed, 55 insertions, 0 deletions
diff --git a/src/main/java/junitparams/internal/parameters/ParametersReader.java b/src/main/java/junitparams/internal/parameters/ParametersReader.java
new file mode 100644
index 0000000..b0f5ec3
--- /dev/null
+++ b/src/main/java/junitparams/internal/parameters/ParametersReader.java
@@ -0,0 +1,55 @@
+package junitparams.internal.parameters;
+
+import java.util.List;
+
+import org.junit.runners.model.FrameworkMethod;
+
+import junitparams.FileParameters;
+import junitparams.Parameters;
+
+import static java.lang.String.*;
+import static java.util.Arrays.*;
+
+public class ParametersReader {
+
+    public static final String ILLEGAL_STATE_EXCEPTION_MESSAGE
+        = format("Illegal usage of JUnitParams in method %s. " +
+                 "Check that you have only used one supported parameters evaluation strategy. " +
+                 "Common case is to use both %s and %s annotations.",
+                 "%s", Parameters.class, FileParameters.class);
+
+    private final FrameworkMethod frameworkMethod;
+    private final List<ParametrizationStrategy> strategies;
+
+    public ParametersReader(Class<?> testClass, FrameworkMethod frameworkMethod) {
+        this.frameworkMethod = frameworkMethod;
+
+        strategies = asList(
+                new ParametersFromCustomProvider(frameworkMethod),
+                new ParametersFromValue(frameworkMethod),
+                new ParametersFromExternalClassProvideMethod(frameworkMethod),
+                new ParametersFromExternalClassMethod(frameworkMethod),
+                new ParametersFromTestClassMethod(frameworkMethod, testClass)
+        );
+    }
+
+    public Object[] read() {
+        boolean strategyAlreadyFound = false;
+        Object[] parameters = new Object[]{};
+
+        for (ParametrizationStrategy strategy : strategies) {
+            if (strategy.isApplicable()) {
+                if (strategyAlreadyFound) {
+                    illegalState();
+                }
+                parameters = strategy.getParameters();
+                strategyAlreadyFound = true;
+            }
+        }
+        return parameters;
+    }
+
+    private void illegalState() {
+        throw new IllegalStateException(format(ILLEGAL_STATE_EXCEPTION_MESSAGE, frameworkMethod.getName()));
+    }
+}