fix generic field type resolve error, for issue #1676

core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderCreator.java

@@ -1346,6 +1346,8 @@ protected void createFieldReader(
 
  int parameterCount = method.getParameterCount();
  if (parameterCount == 0) {
+ Type fieldType = method.getGenericReturnType();
+ Class<?> fieldClass = method.getReturnType();
  FieldReader fieldReader = createFieldReaderMethod(
  objectClass,
  objectType,
@@ -1356,8 +1358,8 @@ protected void createFieldReader(
  fieldInfo.locale,
  fieldInfo.defaultValue,
  fieldInfo.schema,
- method.getGenericReturnType(),
- method.getReturnType(),
+ fieldType,
+ fieldClass,
  method,
  fieldInfo.getInitReader()
  );
@@ -1381,6 +1383,18 @@ protected void createFieldReader(
 
  Type fieldType = method.getGenericParameterTypes()[0];
  Class fieldClass = method.getParameterTypes()[0];
+ if (fieldType instanceof Class && Collection.class.isAssignableFrom((Class<?>) fieldType)) {
+ Class[] interfaces = objectClass.getInterfaces();
+ for (int i = 0; i < interfaces.length; i++) {
+ Method interfaceMethod = BeanUtils.getMethod(interfaces[i], method);
+ Type[] genericParameterTypes = interfaceMethod.getGenericParameterTypes();
+ if (genericParameterTypes.length == 1
+ && genericParameterTypes[0] instanceof ParameterizedType
+ ) {
+ fieldType = genericParameterTypes[0];
+ }
+ }
+ }
 
  // skip function
  if (isFunction(fieldClass)) {
@@ -2146,6 +2160,13 @@ public <T> FieldReader createFieldReaderMethod(
  );
  }
 
+ Type fieldTypeResolved = null;
+ Class fieldClassResolved = null;
+ if (!(fieldType instanceof Class) || !(objectType instanceof Class)) {
+ fieldTypeResolved = BeanUtils.getFieldType(TypeReference.get(objectType), objectClass, method, fieldType);
+ fieldClassResolved = TypeUtils.getMapping(fieldTypeResolved);
+ }
+
  if (method.getParameterCount() == 0) {
  if (fieldClass == AtomicInteger.class) {
  return new FieldReaderAtomicIntegerMethodReadOnly(fieldName, fieldClass, ordinal, jsonSchema, method);
@@ -2180,7 +2201,7 @@ public <T> FieldReader createFieldReaderMethod(
  }
  return new FieldReaderCollectionMethodReadOnly(
  fieldName,
- fieldType,
+ fieldTypeResolved != null ? fieldTypeResolved : fieldType,
  fieldClass,
  ordinal,
  features,
@@ -2216,13 +2237,6 @@ public <T> FieldReader createFieldReaderMethod(
  }
  }
 
- Type fieldTypeResolved = null;
- Class fieldClassResolved = null;
- if (!(fieldType instanceof Class)) {
- fieldTypeResolved = BeanUtils.getFieldType(TypeReference.get(objectType), objectClass, method, fieldType);
- fieldClassResolved = TypeUtils.getMapping(fieldTypeResolved);
- }
-
  if (fieldClass == List.class
  || fieldClass == ArrayList.class
  || fieldClass == LinkedList.class

core/src/main/java/com/alibaba/fastjson2/util/BeanUtils.java

@@ -1639,11 +1639,13 @@ public static Type getFieldType(TypeReference typeReference, Class<?> raw, Membe
  return null;
  }
 
- public static Type getParamType(TypeReference type,
- Class<?> raw,
- Class declaringClass,
- Parameter field,
- Type fieldType) {
+ public static Type getParamType(
+ TypeReference type,
+ Class<?> raw,
+ Class declaringClass,
+ Parameter field,
+ Type fieldType
+ ) {
  while (raw != Object.class) {
  if (declaringClass == raw) {
  return resolve(type.getType(), declaringClass, fieldType);

core/src/test/java/com/alibaba/fastjson2/issues_1600/Issue1676.java

@@ -3,15 +3,39 @@
 import com.alibaba.fastjson2.JSON;
 import org.junit.jupiter.api.Test;
 
+import java.io.Serializable;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.List;
 
-import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class Issue1676 {
  @Test
- public void test() {
+ public void test1() {
+ ParameterizedType parameterizedType = new ParameterizedType() {
+ @Override
+ public Type[] getActualTypeArguments() {
+ return new Type[] {Bean.class};
+ }
+
+ @Override
+ public Type getRawType() {
+ return PageImpl.class;
+ }
+
+ @Override
+ public Type getOwnerType() {
+ return null;
+ }
+ };
+ String s = "{\"current\":1,\"hitCount\":false,\"optimizeCountSql\":true,\"orders\":[],\"pages\":1,\"records\":[{\"name\": \"test\"}],\"searchCount\":true,\"size\":10,\"total\":1}";
+ PageImpl fastJson2PageObject = JSON.parseObject(s, parameterizedType);
+ assertEquals(Bean.class, fastJson2PageObject.getRecords().get(0).getClass());
+ }
+
+ @Test
+ public void test2() {
  ParameterizedType parameterizedType = new ParameterizedType() {
  @Override
  public Type[] getActualTypeArguments() {
@@ -31,10 +55,43 @@ public Type getOwnerType() {
 
  String s = "{\"current\":1,\"hitCount\":false,\"optimizeCountSql\":true,\"orders\":[],\"pages\":1,\"records\":[{\"name\": \"test\"}],\"searchCount\":true,\"size\":10,\"total\":1}";
  Page fastJson2PageObject = JSON.parseObject(s, parameterizedType);
- assertSame(Bean.class, fastJson2PageObject.getRecords().get(0).getClass());
+ assertEquals(Bean.class, fastJson2PageObject.getRecords().get(0).getClass());
  }
 
  public static class Bean {
+ private String name;
+
+ public String getName() {
+ return name;
+ }
+
+ public void setName(String name) {
+ this.name = name;
+ }
+ }
+
+ public interface IPage<T>
+ extends Serializable {
+ List<T> getRecords();
+
+ // 问题出现在这里，如果这里返回结果是IPage<T>，那么fastjson2就会解析有问题，但fastjson1不会有问题；如果返回结果是void也不会有问题
+ IPage<T> setRecords(List<T> records);
+ }
+
+ public static class PageImpl<T>
+ implements IPage<T> {
+ protected List<T> records;
+
+ @Override
+ public List<T> getRecords() {
+ return this.records;
+ }
+
+ @Override
+ public PageImpl<T> setRecords(List<T> records) {
+ this.records = records;
+ return this;
+ }
  }
 
  public static class Page<T> {
@@ -44,8 +101,9 @@ public List<T> getRecords() {
  return records;
  }
 
- public void setRecords(List<T> records) {
+ public Page<T> setRecords(List<T> records) {
  this.records = records;
+ return this;
  }
  }
 }