feat: add agent executor sample

work on #9

jetty/src/test/java/org/bsc/langgraph4j/AgentExecutorStreamingServer.java

@@ -0,0 +1,2 @@
+package org.bsc.langgraph4j;public class AgentExecutorStreamingServer {
+}

jetty/src/test/java/org/bsc/langgraph4j/DotEnvConfig.java

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+package dev.langchain4j;
+
+
+import java.io.FileReader;
+import java.io.Reader;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+
+import static java.util.Optional.ofNullable;
+
+public interface DotEnvConfig {
+
+    static void load()  {
+
+        // Search for .env file
+        Path path = Paths.get(".").toAbsolutePath();
+
+        Path filePath = Paths.get( path.toString(), ".env");
+
+        for( int i=0; !filePath.toFile().exists(); ++i ) {
+            path = path.getParent();
+
+            filePath = Paths.get(path.toString(), ".env");
+
+            if (i == 3) {
+                throw new RuntimeException("no .env file found!");
+            }
+        }
+
+        // load .env contents in System.properties
+        try {
+            final java.util.Properties properties = new java.util.Properties();
+
+            try( Reader r = new FileReader(filePath.toFile())) {
+                properties.load(r);
+            }
+            System.getProperties().putAll(properties);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+
+    static Optional<String> valueOf(String key ) {
+        String value = System.getenv(key);
+        if (value == null) {
+            value = System.getProperty(key);
+        }
+        return ofNullable(value);
+    }
+
+
+}

jetty/src/test/java/org/bsc/langgraph4j/TestTool.java

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+package dev.langchain4j.agentexecutor;
+
+import dev.langchain4j.agent.tool.P;
+import dev.langchain4j.agent.tool.Tool;
+
+import java.util.Optional;
+
+import static java.lang.String.format;
+
+public class TestTool {
+    private String lastResult;
+
+    Optional<String> lastResult() {
+        return Optional.ofNullable(lastResult);
+    }
+
+    @Tool("tool for test AI agent executor")
+    String execTest(@P("test message") String message) {
+
+        lastResult = format( "test tool executed: %s", message);
+        return lastResult;
+    }
+}