Add SftpConfig

* Add SftpConfig and test
* Add package-private AppConfiguration, used by the test
* Add YAML and JSON external configuration files, used by the test

Fixes #420

src/main/java/org/kiwiproject/jsch/SftpConfig.java

@@ -0,0 +1,159 @@
+package org.kiwiproject.jsch;
+
+import static java.util.Objects.isNull;
+import static org.apache.commons.lang3.StringUtils.isBlank;
+
+import io.dropwizard.util.Duration;
+import io.dropwizard.validation.MinDuration;
+import io.dropwizard.validation.PortRange;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
+import java.beans.ConstructorProperties;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * This (Dropwizard) config class allows for common configuration for SFTP access to remote hosts.
+ * <p>
+ * One note on the {@code password} and {@code privateKeyFilePath} fields: the SFTP connector will use either the
+ * password or the private key but not both. If both are specified, the private key will take precedence. This allows
+ * for the greatest flexibility when connecting to different SFTP locations.
+ *
+ * @implNote This uses Dropwizard's {@link Duration} and several Dropwizard validation annotations in addition to the
+ * standard Java Beans Validation annotations, so you will need to ensure the the appropriate Dropwizard JAR files are
+ * on the class/module path.
+ */
+@Getter
+@Setter
+@NoArgsConstructor
+@Builder
+public class SftpConfig {
+
+    private static final int DEFAULT_PORT = 22;
+    private static final String DEFAULT_PREFERRED_AUTHENTICATIONS = "publickey,password";
+    private static final Duration DEFAULT_TIMEOUT = Duration.seconds(5);
+
+    /**
+     * The SFTP port. Default is 22.
+     */
+    @PortRange
+    private int port = DEFAULT_PORT;
+
+    /**
+     * The remote host to connect to via SFTP.
+     */
+    @NotBlank
+    private String host;
+
+    /**
+     * The remote user to connect with via SFTP.
+     */
+    @NotBlank
+    private String user;
+
+    /**
+     * The password, only used if password authentication is used.
+     */
+    private String password;
+
+    /**
+     * The path to the private key file, only used if public key authentication is used.
+     */
+    private String privateKeyFilePath;
+
+    /**
+     * The comma-separated list of preferred authentication mechanisms. Equivalent to the
+     * {@code -o PreferredAuthentications=[gssapi-with-mic|hostbased|publickey|keyboard-interactive|password]} option.
+     * <p>
+     * The default is {@code publickey,password} which differs from the default order in the SFTP command. See
+     * the {@code ssh_info} man page for details.
+     */
+    @NotBlank
+    private String preferredAuthentications = DEFAULT_PREFERRED_AUTHENTICATIONS;
+
+    /**
+     * The root directory of the remote SFTP location, provided as a convenience to store the remote path in the same
+     * place as the other SFTP properties.
+     * <p>
+     * It is not required nor currently used by {@link SftpConnector} or {@link SftpTransfers}.
+     */
+    private String remoteBasePath;
+
+    /**
+     * The local directory to write out any errors if SFTP fails.
+     */
+    @NotBlank
+    private String errorPath;
+
+    /**
+     * The path to the known hosts file.
+     */
+    @NotBlank
+    private String knownHostsFile;
+
+    /**
+     * Provides option to disable strict host key checking, equivalent to the
+     * {@code -o StrictHostKeyChecking=[yes|no]} option.
+     * <p>
+     * The default is false. See the {@code ssh_info} man page for more details.
+     */
+    private boolean disableStrictHostChecking;
+
+    /**
+     * SFTP connection timeout. Default is 5 seconds.
+     *
+     * @implNote The minimum duration annotation of 50 milliseconds is somewhat arbitrary, and is really just intended
+     * to ensure a positive value.
+     */
+    @NotNull
+    @MinDuration(value = 50, unit = TimeUnit.MILLISECONDS)
+    private Duration timeout = DEFAULT_TIMEOUT;
+
+    /**
+     * All-args constructor.
+     *
+     * @implNote This is intentionally not using Lombok because using {@link lombok.AllArgsConstructor} together
+     * with @{@link Builder} results in an all-args constructor that does not respect {@link lombok.Builder.Default}.
+     * As a result we need to handle the defaults ourselves. This is intended to be used during deserialization
+     * from an external configuration file (e.g. a Dropwizard YAML configuration file, or from JSON). Prefer the
+     * builder when constructing programmatically.
+     */
+    // Suppress Sonar's "Methods should not have too many parameters". We need this for the builder and for
+    // deserialization from YAML or JSON configurations.
+    @SuppressWarnings({"java:S107"})
+    @ConstructorProperties({
+            "port", "host", "user", "password",
+            "privateKeyFilePath", "preferredAuthentications",
+            "remoteBasePath", "errorPath", "knownHostsFile",
+            "disableStrictHostChecking", "timeout"
+    })
+    public SftpConfig(int port,
+                      String host,
+                      String user,
+                      String password,
+                      String privateKeyFilePath,
+                      String preferredAuthentications,
+                      String remoteBasePath,
+                      String errorPath,
+                      String knownHostsFile,
+                      boolean disableStrictHostChecking,
+                      Duration timeout) {
+
+        this.port = (port == 0) ? DEFAULT_PORT : port;
+        this.host = host;
+        this.user = user;
+        this.password = password;
+        this.privateKeyFilePath = privateKeyFilePath;
+        this.preferredAuthentications =
+                isBlank(preferredAuthentications) ? DEFAULT_PREFERRED_AUTHENTICATIONS : preferredAuthentications;
+        this.remoteBasePath = remoteBasePath;
+        this.errorPath = errorPath;
+        this.knownHostsFile = knownHostsFile;
+        this.disableStrictHostChecking = disableStrictHostChecking;
+        this.timeout = isNull(timeout) ? DEFAULT_TIMEOUT : timeout;
+    }
+}

src/test/java/org/kiwiproject/jsch/AppConfiguration.java

@@ -0,0 +1,17 @@
+package org.kiwiproject.jsch;
+
+import io.dropwizard.Configuration;
+import lombok.Getter;
+import lombok.Setter;
+
+import javax.validation.Valid;
+import javax.validation.constraints.NotNull;
+
+@Getter
+@Setter
+class AppConfiguration extends Configuration {
+
+    @NotNull
+    @Valid
+    private SftpConfig sftpConfig;
+}