Add history command

Fixes #208

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/History.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed 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 org.springframework.shell.standard.commands;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.shell.standard.ShellComponent;
+import org.springframework.shell.standard.ShellMethod;
+import org.springframework.shell.standard.ShellOption;
+
+/**
+ * A command that displays all previously run commands, optionally dumping to a file readable by {@link Script}.
+ *
+ * @author Eric Bottard
+ */
+@ShellComponent
+public class History {
+
+    private final org.jline.reader.History jLineHistory;
+
+    public History(org.jline.reader.History jLineHistory) {
+        this.jLineHistory = jLineHistory;
+    }
+
+    /**
+     * Marker interface for beans providing {@literal history} functionality to the shell.
+     * <p>
+     * <p>To override the history command, simply register your own bean implementing that interface
+     * and the standard implementation will back off.</p>
+     * <p>
+     * <p>To disable the {@literal history} command entirely, set the {@literal spring.shell.command.history.enabled=false}
+     * property in the environment.</p>
+     *
+     * @author Eric Bottard
+     */
+    public interface Command {
+    }
+
+    @ShellMethod(value = "Display or save the history of previously run commands")
+    public List<String> history(@ShellOption(help = "A file to save history to.", defaultValue = ShellOption.NULL) File file) throws IOException {
+        if (file == null) {
+            List<String> result = new ArrayList<>(jLineHistory.size());
+            jLineHistory.forEach(e -> result.add(e.line()));
+            return result;
+        } else {
+            try (FileWriter w = new FileWriter(file)) {
+                for (org.jline.reader.History.Entry entry : jLineHistory) {
+                    w.append(entry.line()).append(System.lineSeparator());
+                }
+            }
+            return Collections.singletonList(String.format("Wrote %d entries to %s", jLineHistory.size(), file));
+        }
+    }
+}

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/StandardCommandsAutoConfiguration.java

@@ -68,4 +68,11 @@ public class StandardCommandsAutoConfiguration {
 	public Script script(Shell shell, Parser parser) {
 		return new Script(shell, parser);
 	}
+
+	@Bean
+	@ConditionalOnMissingBean(History.Command.class)
+	@ConditionalOnProperty(prefix = "spring.shell.command.history", value = "enabled", havingValue = "true", matchIfMissing = true)
+	public History historyCommand(org.jline.reader.History jLineHistory) {
+		return new History(jLineHistory);
+	}
 }