diff --git a/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java b/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
index 184af52..9fd13b1 100644
--- a/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
+++ b/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
@@ -19,7 +19,10 @@ package de.stklcode.jvault.connector;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import de.stklcode.jvault.connector.exception.*;
-import de.stklcode.jvault.connector.model.*;
+import de.stklcode.jvault.connector.model.AppRole;
+import de.stklcode.jvault.connector.model.AppRoleSecret;
+import de.stklcode.jvault.connector.model.AuthBackend;
+import de.stklcode.jvault.connector.model.Token;
 import de.stklcode.jvault.connector.model.response.*;
 import de.stklcode.jvault.connector.model.response.embedded.AuthMethod;
 import org.apache.http.HttpResponse;
@@ -31,11 +34,16 @@ import org.apache.http.impl.client.CloseableHttpClient;
 import org.apache.http.impl.client.HttpClientBuilder;
 import org.apache.http.util.EntityUtils;
 
-import javax.net.ssl.*;
-import java.io.*;
+import javax.net.ssl.SSLContext;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.UnsupportedEncodingException;
 import java.net.URISyntaxException;
 import java.nio.charset.StandardCharsets;
-import java.util.*;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
 /**
diff --git a/src/main/java/de/stklcode/jvault/connector/VaultConnector.java b/src/main/java/de/stklcode/jvault/connector/VaultConnector.java
index 7284e31..7d7293d 100644
--- a/src/main/java/de/stklcode/jvault/connector/VaultConnector.java
+++ b/src/main/java/de/stklcode/jvault/connector/VaultConnector.java
@@ -21,7 +21,10 @@ import de.stklcode.jvault.connector.exception.VaultConnectorException;
 import de.stklcode.jvault.connector.model.*;
 import de.stklcode.jvault.connector.model.response.*;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 /**
  * Vault Connector interface.
@@ -31,6 +34,9 @@ import java.util.*;
  * @since 0.1
  */
 public interface VaultConnector extends AutoCloseable {
+    /**
+     * Default sub-path for Vault secrets.
+     */
     String PATH_SECRET = "secret";
 
     /**
@@ -115,7 +121,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param appID  The App ID
      * @param userID The User ID
-     * @return TRUE on success
+     * @return The {@link AuthResponse}
      * @throws VaultConnectorException on error
      * @deprecated As of Vault 0.6.1 App-ID is superseded by AppRole. Consider using {@link #authAppRole} instead.
      */
@@ -126,7 +132,7 @@ public interface VaultConnector extends AutoCloseable {
      * Authorize to Vault using AppRole method without secret ID.
      *
      * @param roleID The role ID
-     * @return TRUE on success
+     * @return The {@link AuthResponse}
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -139,7 +145,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param roleID   The role ID
      * @param secretID The secret ID
-     * @return TRUE on success
+     * @return The {@link AuthResponse}
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -151,7 +157,7 @@ public interface VaultConnector extends AutoCloseable {
      * @param appID       The unique App-ID
      * @param policy      The policy to associate with
      * @param displayName Arbitrary name to display
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @deprecated As of Vault 0.6.1 App-ID is superseded by AppRole. Consider using {@link #createAppRole} instead.
      */
@@ -163,7 +169,7 @@ public interface VaultConnector extends AutoCloseable {
      * Register a new AppRole role from given metamodel.
      *
      * @param role The role
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -173,7 +179,7 @@ public interface VaultConnector extends AutoCloseable {
      * Register new AppRole role with default policy.
      *
      * @param roleName The role name
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -186,7 +192,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param roleName The role name
      * @param policies The policies to associate with
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -199,7 +205,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param roleName The role name
      * @param roleID   A custom role ID
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -213,7 +219,7 @@ public interface VaultConnector extends AutoCloseable {
      * @param roleName The role name
      * @param policies The policies to associate with
      * @param roleID   A custom role ID
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -226,7 +232,7 @@ public interface VaultConnector extends AutoCloseable {
      * Delete AppRole role from Vault.
      *
      * @param roleName The role anme
-     * @return TRUE on succevss
+     * @return {@code true} on succevss
      * @throws VaultConnectorException on error
      */
     boolean deleteAppRole(final String roleName) throws VaultConnectorException;
@@ -256,7 +262,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param roleName The role name
      * @param roleID   The role ID
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @since 0.4.0
      */
@@ -345,7 +351,7 @@ public interface VaultConnector extends AutoCloseable {
      *
      * @param appID  The App-ID
      * @param userID The User-ID
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @deprecated As of Vault 0.6.1 App-ID is superseded by AppRole.
      *             Consider using {@link #createAppRoleSecret} instead.
@@ -360,7 +366,7 @@ public interface VaultConnector extends AutoCloseable {
      * @param policy      The policy to associate with
      * @param displayName Arbitrary name to display
      * @param userID      The User-ID
-     * @return TRUE on success
+     * @return {@code true} on success
      * @throws VaultConnectorException on error
      * @deprecated As of Vault 0.6.1 App-ID is superseded by AppRole.
      */
@@ -471,8 +477,9 @@ public interface VaultConnector extends AutoCloseable {
      * @since 0.5.0
      */
     default void writeSecret(final String key, final Map<String, Object> data) throws VaultConnectorException {
-        if (key == null || key.isEmpty())
+        if (key == null || key.isEmpty()) {
             throw new InvalidRequestException("Secret path must not be empty.");
+        }
         write(PATH_SECRET + "/" + key, data);
     }
 
diff --git a/src/main/java/de/stklcode/jvault/connector/exception/InvalidResponseException.java b/src/main/java/de/stklcode/jvault/connector/exception/InvalidResponseException.java
index 2f23cb3..7559d01 100644
--- a/src/main/java/de/stklcode/jvault/connector/exception/InvalidResponseException.java
+++ b/src/main/java/de/stklcode/jvault/connector/exception/InvalidResponseException.java
@@ -38,7 +38,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Constructs a new exception with the specified detail message.
      *
-     * @param message the detail message
+     * @param message The detail message
      */
     public InvalidResponseException(final String message) {
         super(message);
@@ -49,7 +49,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Constructs a new exception with the specified cause.
      *
-     * @param cause the cause
+     * @param cause The cause
      */
     public InvalidResponseException(final Throwable cause) {
         super(cause);
@@ -60,8 +60,8 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Constructs a new exception with the specified detail message and cause.
      *
-     * @param message the detail message
-     * @param cause   the cause
+     * @param message The detail message
+     * @param cause   The cause
      */
     public InvalidResponseException(final String message, final Throwable cause) {
         super(message, cause);
@@ -74,8 +74,8 @@ public final class InvalidResponseException extends VaultConnectorException {
      * <p>
      * The HTTP status code can be retrieved by {@link #getStatusCode()} later.
      *
-     * @param message    the detail message
-     * @param statusCode status code of the HTTP response
+     * @param message    The detail message
+     * @param statusCode Status code of the HTTP response
      * @since 0.6.2
      */
     public InvalidResponseException(final String message, final Integer statusCode) {
@@ -89,9 +89,9 @@ public final class InvalidResponseException extends VaultConnectorException {
      * <p>
      * The HTTP status code can be retrieved by {@link #getStatusCode()} later.
      *
-     * @param message    the detail message
-     * @param statusCode status code of the HTTP response
-     * @param cause      the cause
+     * @param message    The detail message
+     * @param statusCode Status code of the HTTP response
+     * @param cause      The cause
      * @since 0.6.2
      */
     public InvalidResponseException(final String message, final Integer statusCode, final Throwable cause) {
@@ -103,8 +103,8 @@ public final class InvalidResponseException extends VaultConnectorException {
      * <p>
      * The HTTP status code can be retrieved by {@link #getStatusCode()} later.
      *
-     * @param message    the detail message
-     * @param statusCode status code of the HTTP response
+     * @param message    The detail message
+     * @param statusCode Status code of the HTTP response
      * @param response   HTTP response string
      * @since 0.6.2
      */
@@ -121,10 +121,10 @@ public final class InvalidResponseException extends VaultConnectorException {
      * <p>
      * The HTTP status code can be retrieved by {@link #getStatusCode()} later.
      *
-     * @param message    the detail message
-     * @param statusCode status code of the HTTP response
+     * @param message    The detail message
+     * @param statusCode Status code of the HTTP response
      * @param response   HTTP response string
-     * @param cause      the cause
+     * @param cause      The cause
      * @since 0.6.2
      */
     public InvalidResponseException(final String message,
@@ -139,7 +139,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Specify the HTTP status code. Can be retrieved by {@link #getStatusCode()} later.
      *
-     * @param statusCode the status code
+     * @param statusCode The status code
      * @return self
      * @deprecated as of 0.6.2, use constructor with status code argument instead
      */
@@ -151,7 +151,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Specify the response string. Can be retrieved by {@link #getResponse()} later.
      *
-     * @param response response text
+     * @param response Response text
      * @return self
      * @deprecated use constructor with response argument instead
      */
@@ -163,7 +163,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Retrieve the HTTP status code.
      *
-     * @return the status code or {@code null} if none specified.
+     * @return The status code or {@code null} if none specified.
      */
     public Integer getStatusCode() {
         return statusCode;
@@ -172,7 +172,7 @@ public final class InvalidResponseException extends VaultConnectorException {
     /**
      * Retrieve the response text.
      *
-     * @return the response text or {@code null} if none specified.
+     * @return The response text or {@code null} if none specified.
      */
     public String getResponse() {
         return response;
diff --git a/src/main/java/de/stklcode/jvault/connector/factory/HTTPVaultConnectorFactory.java b/src/main/java/de/stklcode/jvault/connector/factory/HTTPVaultConnectorFactory.java
index 3088d8d..64e731a 100644
--- a/src/main/java/de/stklcode/jvault/connector/factory/HTTPVaultConnectorFactory.java
+++ b/src/main/java/de/stklcode/jvault/connector/factory/HTTPVaultConnectorFactory.java
@@ -201,6 +201,7 @@ public final class HTTPVaultConnectorFactory extends VaultConnectorFactory {
             try {
                 numberOfRetries = Integer.parseInt(System.getenv(ENV_VAULT_MAX_RETRIES));
             } catch (NumberFormatException ignored) {
+                /* Ignore malformed values. */
             }
         }