diff --git a/src/main/java/org/gitlab4j/api/models/ApprovedBy.java b/src/main/java/org/gitlab4j/api/models/ApprovedBy.java
index 55271c902..205bb67f0 100644
--- a/src/main/java/org/gitlab4j/api/models/ApprovedBy.java
+++ b/src/main/java/org/gitlab4j/api/models/ApprovedBy.java
@@ -1,6 +1,8 @@
 
 package org.gitlab4j.api.models;
 
+import org.gitlab4j.api.utils.JacksonJson;
+
 import com.fasterxml.jackson.annotation.JsonIgnore;
 
 /**
@@ -48,4 +50,9 @@ public void setGroup(Group group) {
     public Object getApprovedBy() {
 	return (user != null ? user : group);
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/Assignee.java b/src/main/java/org/gitlab4j/api/models/Assignee.java
index 6f3d85273..68497ddb7 100644
--- a/src/main/java/org/gitlab4j/api/models/Assignee.java
+++ b/src/main/java/org/gitlab4j/api/models/Assignee.java
@@ -1,5 +1,12 @@
 
 package org.gitlab4j.api.models;
 
+import org.gitlab4j.api.utils.JacksonJson;
+
 public class Assignee extends AbstractUser<Assignee> {
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/DiffRef.java b/src/main/java/org/gitlab4j/api/models/DiffRef.java
index 9d002b13b..f65f1caad 100644
--- a/src/main/java/org/gitlab4j/api/models/DiffRef.java
+++ b/src/main/java/org/gitlab4j/api/models/DiffRef.java
@@ -1,5 +1,7 @@
 package org.gitlab4j.api.models;
 
+import org.gitlab4j.api.utils.JacksonJson;
+
 public class DiffRef {
     private String baseSha;
     private String headSha;
@@ -31,4 +33,9 @@ public String getStartSha() {
     public void setStartSha(final String startSha) {
         this.startSha = startSha;
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/GroupFilter.java b/src/main/java/org/gitlab4j/api/models/GroupFilter.java
index 3897830f4..8782c7a60 100644
--- a/src/main/java/org/gitlab4j/api/models/GroupFilter.java
+++ b/src/main/java/org/gitlab4j/api/models/GroupFilter.java
@@ -4,6 +4,7 @@
 
 import org.gitlab4j.api.Constants.GroupOrderBy;
 import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.utils.JacksonJson;
 import org.gitlab4j.api.GitLabApiForm;
 
 /**
@@ -160,4 +161,9 @@ public GitLabApiForm getQueryParams() {
             .withParam("top_level_only", topLevelOnly)
         );
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/GroupProjectsFilter.java b/src/main/java/org/gitlab4j/api/models/GroupProjectsFilter.java
index 0cb09b6cf..a797e04a1 100644
--- a/src/main/java/org/gitlab4j/api/models/GroupProjectsFilter.java
+++ b/src/main/java/org/gitlab4j/api/models/GroupProjectsFilter.java
@@ -2,6 +2,7 @@
 
 import org.gitlab4j.api.Constants.ProjectOrderBy;
 import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.utils.JacksonJson;
 import org.gitlab4j.api.GitLabApiForm;
 
 /**
@@ -189,4 +190,9 @@ public GitLabApiForm getQueryParams() {
             .withParam("include_subgroups", includeSubGroups)
         );
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/MergeRequestFilter.java b/src/main/java/org/gitlab4j/api/models/MergeRequestFilter.java
index ddc9700ce..d463a4160 100644
--- a/src/main/java/org/gitlab4j/api/models/MergeRequestFilter.java
+++ b/src/main/java/org/gitlab4j/api/models/MergeRequestFilter.java
@@ -12,6 +12,7 @@
 import org.gitlab4j.api.Constants.MergeRequestSearchIn;
 import org.gitlab4j.api.Constants.MergeRequestState;
 import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.utils.JacksonJson;
 import org.gitlab4j.api.GitLabApiForm;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
@@ -369,4 +370,9 @@ public GitLabApiForm getQueryParams() {
         }
         return params;
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/PipelineFilter.java b/src/main/java/org/gitlab4j/api/models/PipelineFilter.java
index 29ef94494..a149ba881 100644
--- a/src/main/java/org/gitlab4j/api/models/PipelineFilter.java
+++ b/src/main/java/org/gitlab4j/api/models/PipelineFilter.java
@@ -5,6 +5,7 @@
 import org.gitlab4j.api.Constants.PipelineOrderBy;
 import org.gitlab4j.api.Constants.PipelineScope;
 import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.utils.JacksonJson;
 import org.gitlab4j.api.GitLabApiForm;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
@@ -166,4 +167,9 @@ public GitLabApiForm getQueryParams() {
                 .withParam("order_by", orderBy)
                 .withParam("sort", sort));
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/ProjectFilter.java b/src/main/java/org/gitlab4j/api/models/ProjectFilter.java
index 748cd5579..9a167c5e7 100644
--- a/src/main/java/org/gitlab4j/api/models/ProjectFilter.java
+++ b/src/main/java/org/gitlab4j/api/models/ProjectFilter.java
@@ -5,6 +5,7 @@
 import org.gitlab4j.api.Constants;
 import org.gitlab4j.api.Constants.ProjectOrderBy;
 import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.utils.JacksonJson;
 import org.gitlab4j.api.GitLabApiForm;
 
 /**
@@ -389,4 +390,9 @@ public GitLabApiForm getQueryParams() {
             .withParam("topic_id",topic_id)
         );
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }
diff --git a/src/main/java/org/gitlab4j/api/models/Version.java b/src/main/java/org/gitlab4j/api/models/Version.java
index d27aecd93..36d940f13 100644
--- a/src/main/java/org/gitlab4j/api/models/Version.java
+++ b/src/main/java/org/gitlab4j/api/models/Version.java
@@ -1,5 +1,7 @@
 package org.gitlab4j.api.models;
 
+import org.gitlab4j.api.utils.JacksonJson;
+
 public class Version {
 
     private String version;
@@ -20,4 +22,9 @@ public String getRevision() {
     public void setRevision(String revision) {
         this.revision = revision;
     }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
 }