diff --git a/processor/src/main/java/org/mapstruct/ap/model/BeanMapping.java b/processor/src/main/java/org/mapstruct/ap/model/BeanMapping.java
index 66f5a0f86..ee45271dd 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/BeanMapping.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/BeanMapping.java
@@ -62,13 +62,23 @@ public class BeanMapping {
 
     @Override
     public String toString() {
-        StringBuilder stringBuilder = new StringBuilder();
+        StringBuilder sb = new StringBuilder( "BeanMapping {" );
 
-        stringBuilder.append( sourceType );
-        stringBuilder.append( " <=> " );
-        stringBuilder.append( targetType );
+        sb.append( "\n    sourceType=" + sourceType + ',' );
+        sb.append( "\n    targetType=" + targetType + ',' );
 
+        sb.append( "\n    propertyMappings=[\n" );
 
-        return stringBuilder.toString();
+        for ( PropertyMapping propertyMapping : propertyMappings ) {
+            sb.append( "        " + propertyMapping.toString().replaceAll( "\n", "\n        " ) );
+        }
+        sb.append( "\n    ]" );
+
+        sb.append( "\n    mappingMethod=" + mappingMethod.toString().replaceAll( "\n", "\n    " ) + ',' );
+        sb.append( "\n    reverseMappingMethod=" + reverseMappingMethod + ',' );
+        sb.append( "\n    isIterableMapping=" + isIterableMapping );
+        sb.append( "\n}" );
+
+        return sb.toString();
     }
 }
diff --git a/processor/src/main/java/org/mapstruct/ap/model/Mapper.java b/processor/src/main/java/org/mapstruct/ap/model/Mapper.java
index d0f0a9b8a..36df57728 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/Mapper.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/Mapper.java
@@ -34,6 +34,25 @@ public class Mapper {
         this.usedMapperTypes = usedMapperTypes;
     }
 
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder( "Mapper {" );
+
+        sb.append( "\n    packageName='" + packageName + "\'," );
+        sb.append( "\n    interfaceName='" + interfaceName + "\'," );
+        sb.append( "\n    implementationName='" + implementationName + "\'," );
+        sb.append( "\n    beanMappings=[" );
+
+        for ( BeanMapping beanMapping : beanMappings ) {
+            sb.append( "\n        " + beanMapping.toString().replaceAll( "\n", "\n        " ) );
+        }
+        sb.append( "\n    ]" );
+        sb.append( "\n    usedMapperTypes=" + usedMapperTypes );
+        sb.append( "\n}," );
+
+        return sb.toString();
+    }
+
     public String getPackageName() {
         return packageName;
     }
diff --git a/processor/src/main/java/org/mapstruct/ap/model/MappingMethod.java b/processor/src/main/java/org/mapstruct/ap/model/MappingMethod.java
index 3d206e143..723831955 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/MappingMethod.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/MappingMethod.java
@@ -55,4 +55,13 @@ public class MappingMethod {
     public boolean isGenerationRequired() {
         return declaringMapper == null;
     }
+
+    @Override
+    public String toString() {
+        return "MappingMethod {" +
+            "\n    name='" + name + "\'," +
+            "\n    parameterName='" + parameterName + "\'," +
+            "\n    elementMappingMethod=" + elementMappingMethod +
+            "\n}";
+    }
 }
diff --git a/processor/src/main/java/org/mapstruct/ap/model/PropertyMapping.java b/processor/src/main/java/org/mapstruct/ap/model/PropertyMapping.java
index 90394e480..b1ca022b0 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/PropertyMapping.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/PropertyMapping.java
@@ -68,4 +68,18 @@ public class PropertyMapping {
     public String getFromConversion() {
         return fromConversion;
     }
+
+    @Override
+    public String toString() {
+        return "PropertyMapping {" +
+            "\n    sourceName='" + sourceName + "\'," +
+            "\n    sourceType=" + sourceType + "," +
+            "\n    targetName='" + targetName + "\'," +
+            "\n    targetType=" + targetType + "," +
+            "\n    mappingMethod=" + mappingMethod + "," +
+            "\n    reverseMappingMethod=" + reverseMappingMethod + "," +
+            "\n    toConversion='" + toConversion + "\'," +
+            "\n    fromConversion='" + fromConversion + "\'," +
+            "\n}";
+    }
 }