refactor: Extract form-body schema coercion from FormUrlEncodedParser

Author: thced

src/main/java/com/retailsvc/http/internal/FormBodyCoercion.java

@@ -0,0 +1,45 @@
+package com.retailsvc.http.internal;
+
+import com.retailsvc.http.spec.schema.ArraySchema;
+import com.retailsvc.http.spec.schema.ObjectSchema;
+import com.retailsvc.http.spec.schema.Schema;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Coerces string-typed values produced by {@link FormUrlEncodedParser} into the Java types
+ * described by the body schema (numbers, booleans, arrays). Called by {@link
+ * RequestPreparationFilter} after parsing, before validation.
+ */
+final class FormBodyCoercion {
+
+  private FormBodyCoercion() {}
+
+  static Map<String, Object> coerce(Map<String, Object> parsed, Schema schema) {
+    if (!(schema instanceof ObjectSchema obj)) {
+      return parsed;
+    }
+    Map<String, Schema> properties = obj.properties();
+    for (Map.Entry<String, Object> e : parsed.entrySet()) {
+      Schema propSchema = properties.get(e.getKey());
+      if (propSchema == null) {
+        continue;
+      }
+      String pointer = "/" + e.getKey();
+      Object value = e.getValue();
+      if (propSchema instanceof ArraySchema arr && value instanceof List<?> list) {
+        List<Object> coerced = new ArrayList<>(list.size());
+        for (int i = 0; i < list.size(); i++) {
+          coerced.add(ValueCoercion.coerce((String) list.get(i), arr.items(), pointer + "/" + i));
+        }
+        e.setValue(coerced);
+      } else if (propSchema instanceof ArraySchema arr && value instanceof String s) {
+        e.setValue(List.of(ValueCoercion.coerce(s, arr.items(), pointer + "/0")));
+      } else if (value instanceof String s) {
+        e.setValue(ValueCoercion.coerce(s, propSchema, pointer));
+      }
+    }
+    return parsed;
+  }
+}

src/main/java/com/retailsvc/http/internal/FormUrlEncodedParser.java

@@ -1,9 +1,6 @@
 package com.retailsvc.http.internal;
 
 import com.retailsvc.http.ValidationException;
-import com.retailsvc.http.spec.schema.ArraySchema;
-import com.retailsvc.http.spec.schema.ObjectSchema;
-import com.retailsvc.http.spec.schema.Schema;
 import com.retailsvc.http.validate.ValidationError;
 import java.net.URLDecoder;
 import java.nio.charset.Charset;
@@ -71,35 +68,6 @@ private static void addEntry(Map<String, Object> out, String key, String value)
         });
   }
 
-  /** Returns the parsed map after coercing field values against the given body schema. */
-  public Map<String, Object> parseAndCoerce(byte[] body, String contentTypeHeader, Schema schema) {
-    Map<String, Object> parsed = parse(body, contentTypeHeader);
-    if (!(schema instanceof ObjectSchema obj)) {
-      return parsed;
-    }
-    Map<String, Schema> properties = obj.properties();
-    for (Map.Entry<String, Object> e : parsed.entrySet()) {
-      Schema propSchema = properties.get(e.getKey());
-      if (propSchema == null) {
-        continue;
-      }
-      String pointer = "/" + e.getKey();
-      Object value = e.getValue();
-      if (propSchema instanceof ArraySchema arr && value instanceof List<?> list) {
-        List<Object> coerced = new ArrayList<>(list.size());
-        for (int i = 0; i < list.size(); i++) {
-          coerced.add(ValueCoercion.coerce((String) list.get(i), arr.items(), pointer + "/" + i));
-        }
-        e.setValue(coerced);
-      } else if (propSchema instanceof ArraySchema arr && value instanceof String s) {
-        e.setValue(List.of(ValueCoercion.coerce(s, arr.items(), pointer + "/0")));
-      } else if (value instanceof String s) {
-        e.setValue(ValueCoercion.coerce(s, propSchema, pointer));
-      }
-    }
-    return parsed;
-  }
-
   private static Charset resolveCharset(String header) {
     return ContentTypeHeader.parameter(header, "charset")
         .map(FormUrlEncodedParser::safeCharset)

src/main/java/com/retailsvc/http/internal/RequestPreparationFilter.java

@@ -153,7 +153,7 @@ private Object validateAndParseBody(HttpExchange exchange, Operation op, byte[]
     Object parsed =
         switch (mediaType) {
           case "application/x-www-form-urlencoded" ->
-              formParser.parseAndCoerce(body, header, mt.schema());
+              FormBodyCoercion.coerce(formParser.parse(body, header), mt.schema());
           case "text/plain" -> textParser.parse(body, header);
           default -> jsonMapper.mapFrom(body);
         };

src/test/java/com/retailsvc/http/internal/FormUrlEncodedParserTest.java

@@ -84,7 +84,8 @@ void coercesIntegerProperty() {
     ObjectSchema bodySchema = anObjectSchema(Map.of("age", intSchema));
 
     Map<String, Object> out =
-        parser.parseAndCoerce("age=30".getBytes(StandardCharsets.UTF_8), null, bodySchema);
+        FormBodyCoercion.coerce(
+            parser.parse("age=30".getBytes(StandardCharsets.UTF_8), null), bodySchema);
 
     assertThat(out).containsExactly(Map.entry("age", 30L));
   }
@@ -96,7 +97,8 @@ void coercesArrayOfIntegersProperty() {
     ObjectSchema bodySchema = anObjectSchema(Map.of("ids", arrSchema));
 
     Map<String, Object> out =
-        parser.parseAndCoerce("ids=1&ids=2".getBytes(StandardCharsets.UTF_8), null, bodySchema);
+        FormBodyCoercion.coerce(
+            parser.parse("ids=1&ids=2".getBytes(StandardCharsets.UTF_8), null), bodySchema);
 
     assertThat(out).containsExactly(Map.entry("ids", List.of(1L, 2L)));
   }
@@ -108,7 +110,8 @@ void coercionFailureThrowsValidationExceptionAtPropertyPointer() {
 
     org.assertj.core.api.Assertions.assertThatThrownBy(
             () ->
-                parser.parseAndCoerce("age=abc".getBytes(StandardCharsets.UTF_8), null, bodySchema))
+                FormBodyCoercion.coerce(
+                    parser.parse("age=abc".getBytes(StandardCharsets.UTF_8), null), bodySchema))
         .isInstanceOf(com.retailsvc.http.ValidationException.class)
         .extracting("error.pointer", "error.keyword")
         .containsExactly("/age", "type");
@@ -119,7 +122,8 @@ void unknownPropertyPassesThroughUnchanged() {
     ObjectSchema bodySchema = anObjectSchema(Map.of());
 
     Map<String, Object> out =
-        parser.parseAndCoerce("anything=v".getBytes(StandardCharsets.UTF_8), null, bodySchema);
+        FormBodyCoercion.coerce(
+            parser.parse("anything=v".getBytes(StandardCharsets.UTF_8), null), bodySchema);
 
     assertThat(out).containsExactly(Map.entry("anything", "v"));
   }
@@ -129,7 +133,8 @@ void nonObjectSchemaReturnsRawMap() {
     StringSchema strSchema = aStringSchema();
 
     Map<String, Object> out =
-        parser.parseAndCoerce("a=1".getBytes(StandardCharsets.UTF_8), null, strSchema);
+        FormBodyCoercion.coerce(
+            parser.parse("a=1".getBytes(StandardCharsets.UTF_8), null), strSchema);
 
     assertThat(out).containsExactly(Map.entry("a", "1"));
   }