fix NPE in deserialize

cursorpaging-jpa-api/src/main/java/io/vigier/cursorpaging/jpa/serializer/RequestSerializer.java

@@ -4,7 +4,6 @@
 import io.vigier.cursorpaging.jpa.Attribute;
 import io.vigier.cursorpaging.jpa.PageRequest;
 import io.vigier.cursorpaging.jpa.serializer.dto.Cursor;
-import java.time.Instant;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -15,7 +14,6 @@
 import lombok.Getter;
 import lombok.SneakyThrows;
 import org.springframework.core.convert.ConversionService;
-import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.lang.Nullable;
 
 @Builder
@@ -31,53 +29,7 @@ public class RequestSerializer<E> {
     private Class<E> entityType;
 
     @Builder.Default
-    private final ConversionService conversionService = new ConversionService() {
-        @Override
-        public boolean canConvert( final Class<?> sourceType, final Class<?> targetType ) {
-            if ( sourceType == null || targetType == null ) {
-                return false;
-            }
-            return sourceType.isAssignableFrom( String.class ) && (targetType.isAssignableFrom( Long.class )
-                    || targetType.isAssignableFrom( Integer.class ) || targetType.isAssignableFrom( Boolean.class )
-                    || targetType.isAssignableFrom( String.class ) || targetType.isAssignableFrom( Object.class ));
-        }
-
-        @Override
-        public boolean canConvert( final TypeDescriptor sourceType, final TypeDescriptor targetType ) {
-            if ( sourceType == null || targetType == null ) {
-                return false;
-            }
-            return canConvert( sourceType.getType(), targetType.getType() );
-        }
-
-        @Override
-        public <T> T convert( final Object source, final Class<T> targetType ) {
-            if ( targetType == String.class ) {
-                return targetType.cast( source.toString() );
-            }
-            if ( targetType == Integer.class ) {
-                return targetType.cast( Integer.valueOf( source.toString() ) );
-            }
-            if ( targetType == Long.class ) {
-                return targetType.cast( Long.valueOf( source.toString() ) );
-            }
-            if ( targetType == Boolean.class ) {
-                return targetType.cast( source.toString().equals( "true" ) );
-            }
-            if ( targetType == Instant.class ) {
-                return targetType.cast( Instant.parse( source.toString() ) );
-            }
-            if ( targetType == Object.class ) {
-                return targetType.cast( source );
-            }
-            return null;
-        }
-
-        @Override
-        public Object convert( final Object source, final TypeDescriptor sourceType, final TypeDescriptor targetType ) {
-            return convert( source, targetType.getObjectType() );
-        }
-    };
+    private final ConversionService conversionService = new SimpleConversionService();
 
     @Builder.Default
     private final Map<String, RuleFactory> filterRuleFactories = new HashMap<>();

cursorpaging-jpa-api/src/main/java/io/vigier/cursorpaging/jpa/serializer/RequestSerializerFactory.java

@@ -20,7 +20,8 @@
 @RequiredArgsConstructor
 public class RequestSerializerFactory {
 
-    private final ConversionService conversionService;
+    @Builder.Default
+    private final ConversionService conversionService = new SimpleConversionService();
 
     @Builder.Default
     private final Encrypter encrypter = Encrypter.getInstance();
@@ -46,6 +47,11 @@ public static RequestSerializerFactory create( final Consumer<RequestSerializerF
         return b.build();
     }
 
+    public static RequestSerializerFactory create() {
+        return RequestSerializerFactory.builder()
+                .build();
+    }
+
     @SuppressWarnings( "unchecked" )
     public <T> RequestSerializer<T> forEntity( final Class<T> entityClass ) {
         return (RequestSerializer<T>) entitySerializers.computeIfAbsent( entityClass,

cursorpaging-jpa-api/src/main/java/io/vigier/cursorpaging/jpa/serializer/SimpleConversionService.java

@@ -0,0 +1,57 @@
+package io.vigier.cursorpaging.jpa.serializer;
+
+import java.time.Instant;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
+
+/**
+ * Very simple conversion service which might help to do create some test without the need of setting up a more
+ * sophisticated conversion service, but is not meant to be used in production.
+ */
+class SimpleConversionService implements ConversionService {
+    @Override
+    public boolean canConvert( final Class<?> sourceType, final Class<?> targetType ) {
+        if ( sourceType == null || targetType == null ) {
+            return false;
+        }
+        return sourceType.isAssignableFrom( String.class ) && (targetType.isAssignableFrom( Long.class )
+                || targetType.isAssignableFrom( Integer.class ) || targetType.isAssignableFrom( Boolean.class )
+                || targetType.isAssignableFrom( String.class ) || targetType.isAssignableFrom( Object.class ));
+    }
+
+    @Override
+    public boolean canConvert( final TypeDescriptor sourceType, final TypeDescriptor targetType ) {
+        if ( sourceType == null || targetType == null ) {
+            return false;
+        }
+        return canConvert( sourceType.getType(), targetType.getType() );
+    }
+
+    @Override
+    public <T> T convert( final Object source, final Class<T> targetType ) {
+        if ( targetType == String.class ) {
+            return targetType.cast( source.toString() );
+        }
+        if ( targetType == Integer.class ) {
+            return targetType.cast( Integer.valueOf( source.toString() ) );
+        }
+        if ( targetType == Long.class ) {
+            return targetType.cast( Long.valueOf( source.toString() ) );
+        }
+        if ( targetType == Boolean.class ) {
+            return targetType.cast( "true".equals( source.toString() ) );
+        }
+        if ( targetType == Instant.class ) {
+            return targetType.cast( Instant.parse( source.toString() ) );
+        }
+        if ( targetType == Object.class ) {
+            return targetType.cast( source );
+        }
+        return null;
+    }
+
+    @Override
+    public Object convert( final Object source, final TypeDescriptor sourceType, final TypeDescriptor targetType ) {
+        return convert( source, targetType.getObjectType() );
+    }
+}