Move parsing of JSON response into RequestHelper

The pattern is always the same, issue request, parse String response
into target class and catch exceptions. Bundle these blocks in the
helper class for GET, POST and PUT methods to reduce overhead in the
actual connector.

src/main/java/de/stklcode/jvault/connector/internal/RequestHelper.java

@@ -96,6 +96,27 @@ public final class RequestHelper implements Serializable {
         return request(post, retries);
     }
 
+    /**
+     * Execute HTTP request using POST method and parse JSON result.
+     *
+     * @param path    URL path (relative to base).
+     * @param payload Map of payload values (will be converted to JSON).
+     * @param token   Vault token (may be {@code null}).
+     * @param target  Target class.
+     * @return HTTP response
+     * @throws VaultConnectorException on connection error
+     * @since 0.8
+     */
+    public <T> T post(final String path, final Object payload, final String token, final Class<T> target)
+            throws VaultConnectorException {
+        try {
+            String response = post(path, payload, token);
+            return jsonMapper.readValue(response, target);
+        } catch (IOException e) {
+            throw new InvalidResponseException(Error.PARSE_RESPONSE, e);
+        }
+    }
+
     /**
      * Execute HTTP request using PUT method.
      *
@@ -129,6 +150,27 @@ public final class RequestHelper implements Serializable {
         return request(put, retries);
     }
 
+    /**
+     * Execute HTTP request using PUT method and parse JSON result.
+     *
+     * @param path    URL path (relative to base).
+     * @param payload Map of payload values (will be converted to JSON).
+     * @param token   Vault token (may be {@code null}).
+     * @param target  Target class.
+     * @return HTTP response
+     * @throws VaultConnectorException on connection error
+     * @since 0.8
+     */
+    public <T> T put(final String path, final Map<String, String> payload, final String token, final Class<T> target)
+            throws VaultConnectorException {
+        try {
+            String response = put(path, payload, token);
+            return jsonMapper.readValue(response, target);
+        } catch (IOException e) {
+            throw new InvalidResponseException(Error.PARSE_RESPONSE, e);
+        }
+    }
+
     /**
      * Execute HTTP request using DELETE method.
      *
@@ -158,17 +200,22 @@ public final class RequestHelper implements Serializable {
      * @param token   Vault token (may be {@code null}).
      * @return HTTP response
      * @throws VaultConnectorException on connection error
-     * @throws URISyntaxException      on invalid URI syntax
      * @since 0.8 Added {@code token} parameter.
      */
     public String get(final String path, final Map<String, String> payload, final String token)
-            throws VaultConnectorException, URISyntaxException {
-        /* Add parameters to URI */
-        URIBuilder uriBuilder = new URIBuilder(baseURL + path);
-        payload.forEach(uriBuilder::addParameter);
+            throws VaultConnectorException {
+        HttpGet get;
+        try {
+            /* Add parameters to URI */
+            URIBuilder uriBuilder = new URIBuilder(baseURL + path);
+            payload.forEach(uriBuilder::addParameter);
 
-        /* Initialize request */
-        HttpGet get = new HttpGet(uriBuilder.build());
+            /* Initialize request */
+            get = new HttpGet(uriBuilder.build());
+        } catch (URISyntaxException e) {
+            /* this should never occur and may leak sensible information */
+            throw new InvalidRequestException(Error.URI_FORMAT);
+        }
 
         /* Set X-Vault-Token header */
         if (token != null) {
@@ -178,6 +225,27 @@ public final class RequestHelper implements Serializable {
         return request(get, retries);
     }
 
+    /**
+     * Execute HTTP request using GET method and parse JSON result to target class.
+     *
+     * @param path    URL path (relative to base).
+     * @param payload Map of payload values (will be converted to JSON).
+     * @param token   Vault token (may be {@code null}).
+     * @param target  Target class.
+     * @return HTTP response
+     * @throws VaultConnectorException on connection error
+     * @since 0.8
+     */
+    public <T> T get(final String path, final Map<String, String> payload, final String token, final Class<T> target)
+            throws VaultConnectorException {
+        try {
+            String response = get(path, payload, token);
+            return jsonMapper.readValue(response, target);
+        } catch (IOException e) {
+            throw new InvalidResponseException(Error.PARSE_RESPONSE, e);
+        }
+    }
+
     /**
      * Execute prepared HTTP request and return result.
      *