When javaType has not (or partially) been specified, determine the best matching constructor

src/main/java/org/apache/ibatis/builder/MapperBuilderAssistant.java

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2009-2024 the original author or authors.
+ *    Copyright 2009-2025 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -466,5 +466,4 @@ private Class<?> resolveParameterJavaType(Class<?> resultType, String property,
     }
     return javaType;
   }
-
 }

src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2009-2024 the original author or authors.
+ *    Copyright 2009-2025 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -63,6 +63,7 @@
 import org.apache.ibatis.builder.CacheRefResolver;
 import org.apache.ibatis.builder.IncompleteElementException;
 import org.apache.ibatis.builder.MapperBuilderAssistant;
+import org.apache.ibatis.builder.ResultMappingConstructorResolver;
 import org.apache.ibatis.builder.xml.XMLMapperBuilder;
 import org.apache.ibatis.cursor.Cursor;
 import org.apache.ibatis.executor.keygen.Jdbc3KeyGenerator;
@@ -237,7 +238,7 @@ private String generateResultMapName(Method method) {
   private void applyResultMap(String resultMapId, Class<?> returnType, Arg[] args, Result[] results,
       TypeDiscriminator discriminator) {
     List<ResultMapping> resultMappings = new ArrayList<>();
-    applyConstructorArgs(args, returnType, resultMappings);
+    applyConstructorArgs(args, returnType, resultMappings, resultMapId);
     applyResults(results, returnType, resultMappings);
     Discriminator disc = applyDiscriminator(resultMapId, returnType, discriminator);
     // TODO add AutoMappingBehaviour
@@ -251,7 +252,7 @@ private void createDiscriminatorResultMaps(String resultMapId, Class<?> resultTy
         String caseResultMapId = resultMapId + "-" + c.value();
         List<ResultMapping> resultMappings = new ArrayList<>();
         // issue #136
-        applyConstructorArgs(c.constructArgs(), resultType, resultMappings);
+        applyConstructorArgs(c.constructArgs(), resultType, resultMappings, resultMapId);
         applyResults(c.results(), resultType, resultMappings);
         // TODO add AutoMappingBehaviour
         assistant.addResultMap(caseResultMapId, c.type(), resultMapId, null, resultMappings, null);
@@ -461,15 +462,15 @@ private void applyResults(Result[] results, Class<?> resultType, List<ResultMapp
 
   private String findColumnPrefix(Result result) {
     String columnPrefix = result.one().columnPrefix();
-    if (columnPrefix.length() < 1) {
+    if (columnPrefix.isEmpty()) {
       columnPrefix = result.many().columnPrefix();
     }
     return columnPrefix;
   }
 
   private String nestedResultMapId(Result result) {
     String resultMapId = result.one().resultMap();
-    if (resultMapId.length() < 1) {
+    if (resultMapId.isEmpty()) {
       resultMapId = result.many().resultMap();
     }
     if (!resultMapId.contains(".")) {
@@ -479,15 +480,15 @@ private String nestedResultMapId(Result result) {
   }
 
   private boolean hasNestedResultMap(Result result) {
-    if (result.one().resultMap().length() > 0 && result.many().resultMap().length() > 0) {
+    if (!result.one().resultMap().isEmpty() && !result.many().resultMap().isEmpty()) {
       throw new BuilderException("Cannot use both @One and @Many annotations in the same @Result");
     }
-    return result.one().resultMap().length() > 0 || result.many().resultMap().length() > 0;
+    return !result.one().resultMap().isEmpty() || !result.many().resultMap().isEmpty();
   }
 
   private String nestedSelectId(Result result) {
     String nestedSelect = result.one().select();
-    if (nestedSelect.length() < 1) {
+    if (nestedSelect.isEmpty()) {
       nestedSelect = result.many().select();
     }
     if (!nestedSelect.contains(".")) {
@@ -498,22 +499,24 @@ private String nestedSelectId(Result result) {
 
   private boolean isLazy(Result result) {
     boolean isLazy = configuration.isLazyLoadingEnabled();
-    if (result.one().select().length() > 0 && FetchType.DEFAULT != result.one().fetchType()) {
+    if (!result.one().select().isEmpty() && FetchType.DEFAULT != result.one().fetchType()) {
       isLazy = result.one().fetchType() == FetchType.LAZY;
-    } else if (result.many().select().length() > 0 && FetchType.DEFAULT != result.many().fetchType()) {
+    } else if (!result.many().select().isEmpty() && FetchType.DEFAULT != result.many().fetchType()) {
       isLazy = result.many().fetchType() == FetchType.LAZY;
     }
     return isLazy;
   }
 
   private boolean hasNestedSelect(Result result) {
-    if (result.one().select().length() > 0 && result.many().select().length() > 0) {
+    if (!result.one().select().isEmpty() && !result.many().select().isEmpty()) {
       throw new BuilderException("Cannot use both @One and @Many annotations in the same @Result");
     }
-    return result.one().select().length() > 0 || result.many().select().length() > 0;
+    return !result.one().select().isEmpty() || !result.many().select().isEmpty();
   }
 
-  private void applyConstructorArgs(Arg[] args, Class<?> resultType, List<ResultMapping> resultMappings) {
+  private void applyConstructorArgs(Arg[] args, Class<?> resultType, List<ResultMapping> resultMappings,
+      String resultMapId) {
+    final List<ResultMapping> mappings = new ArrayList<>();
     for (Arg arg : args) {
       List<ResultFlag> flags = new ArrayList<>();
       flags.add(ResultFlag.CONSTRUCTOR);
@@ -527,12 +530,16 @@ private void applyConstructorArgs(Arg[] args, Class<?> resultType, List<ResultMa
           nullOrEmpty(arg.column()), arg.javaType() == void.class ? null : arg.javaType(),
           arg.jdbcType() == JdbcType.UNDEFINED ? null : arg.jdbcType(), nullOrEmpty(arg.select()),
           nullOrEmpty(arg.resultMap()), null, nullOrEmpty(arg.columnPrefix()), typeHandler, flags, null, null, false);
-      resultMappings.add(resultMapping);
+      mappings.add(resultMapping);
     }
+
+    final ResultMappingConstructorResolver resolver = new ResultMappingConstructorResolver(configuration, mappings,
+        resultType, resultMapId);
+    resultMappings.addAll(resolver.resolveWithConstructor());
   }
 
   private String nullOrEmpty(String value) {
-    return value == null || value.trim().length() == 0 ? null : value;
+    return value == null || value.trim().isEmpty() ? null : value;
   }
 
   private KeyGenerator handleSelectKeyAnnotation(SelectKey selectKeyAnnotation, String baseStatementId,

src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2009-2024 the original author or authors.
+ *    Copyright 2009-2025 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@
 import org.apache.ibatis.builder.IncompleteElementException;
 import org.apache.ibatis.builder.MapperBuilderAssistant;
 import org.apache.ibatis.builder.ResultMapResolver;
+import org.apache.ibatis.builder.ResultMappingConstructorResolver;
 import org.apache.ibatis.cache.Cache;
 import org.apache.ibatis.executor.ErrorContext;
 import org.apache.ibatis.io.Resources;
@@ -223,12 +224,17 @@ private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> addi
     if (typeClass == null) {
       typeClass = inheritEnclosingType(resultMapNode, enclosingType);
     }
+
+    String id = resultMapNode.getStringAttribute("id", resultMapNode::getValueBasedIdentifier);
+    String extend = resultMapNode.getStringAttribute("extends");
+    Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
+
     Discriminator discriminator = null;
     List<ResultMapping> resultMappings = new ArrayList<>(additionalResultMappings);
     List<XNode> resultChildren = resultMapNode.getChildren();
     for (XNode resultChild : resultChildren) {
       if ("constructor".equals(resultChild.getName())) {
-        processConstructorElement(resultChild, typeClass, resultMappings);
+        processConstructorElement(resultChild, typeClass, resultMappings, id);
       } else if ("discriminator".equals(resultChild.getName())) {
         discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
       } else {
@@ -239,9 +245,7 @@ private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> addi
         resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
       }
     }
-    String id = resultMapNode.getStringAttribute("id", resultMapNode::getValueBasedIdentifier);
-    String extend = resultMapNode.getStringAttribute("extends");
-    Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
+
     ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator,
         resultMappings, autoMapping);
     try {
@@ -265,16 +269,24 @@ protected Class<?> inheritEnclosingType(XNode resultMapNode, Class<?> enclosingT
     return null;
   }
 
-  private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings) {
+  private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings,
+      String id) {
     List<XNode> argChildren = resultChild.getChildren();
+
+    final List<ResultMapping> mappings = new ArrayList<>();
     for (XNode argChild : argChildren) {
       List<ResultFlag> flags = new ArrayList<>();
       flags.add(ResultFlag.CONSTRUCTOR);
       if ("idArg".equals(argChild.getName())) {
         flags.add(ResultFlag.ID);
       }
-      resultMappings.add(buildResultMappingFromContext(argChild, resultType, flags));
+
+      mappings.add(buildResultMappingFromContext(argChild, resultType, flags));
     }
+
+    final ResultMappingConstructorResolver resolver = new ResultMappingConstructorResolver(configuration, mappings,
+        resultType, id);
+    resultMappings.addAll(resolver.resolveWithConstructor());
   }
 
   private Discriminator processDiscriminatorElement(XNode context, Class<?> resultType,

src/main/java/org/apache/ibatis/mapping/ResultMap.java

@@ -15,20 +15,13 @@
  */
 package org.apache.ibatis.mapping;
 
-import java.lang.annotation.Annotation;
-import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Set;
 
-import org.apache.ibatis.annotations.Param;
-import org.apache.ibatis.builder.BuilderException;
-import org.apache.ibatis.logging.Log;
-import org.apache.ibatis.logging.LogFactory;
-import org.apache.ibatis.reflection.ParamNameUtil;
 import org.apache.ibatis.session.Configuration;
 
 /**
@@ -55,8 +48,6 @@ private ResultMap() {
   }
 
   public static class Builder {
-    private static final Log log = LogFactory.getLog(Builder.class);
-
     private final ResultMap resultMap = new ResultMap();
 
     public Builder(Configuration configuration, String id, Class<?> type, List<ResultMapping> resultMappings) {
@@ -85,16 +76,18 @@ public ResultMap build() {
       if (resultMap.id == null) {
         throw new IllegalArgumentException("ResultMaps must have an id");
       }
+
       resultMap.mappedColumns = new HashSet<>();
       resultMap.mappedProperties = new HashSet<>();
       resultMap.idResultMappings = new ArrayList<>();
       resultMap.constructorResultMappings = new ArrayList<>();
       resultMap.propertyResultMappings = new ArrayList<>();
-      final List<String> constructorArgNames = new ArrayList<>();
+
       for (ResultMapping resultMapping : resultMap.resultMappings) {
         resultMap.hasNestedQueries = resultMap.hasNestedQueries || resultMapping.getNestedQueryId() != null;
         resultMap.hasNestedResultMaps = resultMap.hasNestedResultMaps
             || resultMapping.getNestedResultMapId() != null && resultMapping.getResultSet() == null;
+
         final String column = resultMapping.getColumn();
         if (column != null) {
           resultMap.mappedColumns.add(column.toUpperCase(Locale.ENGLISH));
@@ -106,10 +99,12 @@ public ResultMap build() {
             }
           }
         }
+
         final String property = resultMapping.getProperty();
         if (property != null) {
           resultMap.mappedProperties.add(property);
         }
+
         if (resultMapping.getFlags().contains(ResultFlag.CONSTRUCTOR)) {
           resultMap.constructorResultMappings.add(resultMapping);
 
@@ -118,99 +113,27 @@ public ResultMap build() {
           resultMap.hasResultMapsUsingConstructorCollection = resultMap.hasResultMapsUsingConstructorCollection
               || (resultMapping.getNestedQueryId() == null && resultMapping.getTypeHandler() == null && javaType != null
                   && resultMap.configuration.getObjectFactory().isCollection(javaType));
-
-          if (resultMapping.getProperty() != null) {
-            constructorArgNames.add(resultMapping.getProperty());
-          }
         } else {
           resultMap.propertyResultMappings.add(resultMapping);
         }
+
         if (resultMapping.getFlags().contains(ResultFlag.ID)) {
           resultMap.idResultMappings.add(resultMapping);
         }
       }
+
       if (resultMap.idResultMappings.isEmpty()) {
         resultMap.idResultMappings.addAll(resultMap.resultMappings);
       }
-      if (!constructorArgNames.isEmpty()) {
-        final List<String> actualArgNames = argNamesOfMatchingConstructor(constructorArgNames);
-        if (actualArgNames == null) {
-          throw new BuilderException("Error in result map '" + resultMap.id + "'. Failed to find a constructor in '"
-              + resultMap.getType().getName() + "' with arg names " + constructorArgNames
-              + ". Note that 'javaType' is required when there is no writable property with the same name ('name' is optional, BTW). There might be more info in debug log.");
-        }
-        resultMap.constructorResultMappings.sort((o1, o2) -> {
-          int paramIdx1 = actualArgNames.indexOf(o1.getProperty());
-          int paramIdx2 = actualArgNames.indexOf(o2.getProperty());
-          return paramIdx1 - paramIdx2;
-        });
-      }
+
       // lock down collections
       resultMap.resultMappings = Collections.unmodifiableList(resultMap.resultMappings);
       resultMap.idResultMappings = Collections.unmodifiableList(resultMap.idResultMappings);
       resultMap.constructorResultMappings = Collections.unmodifiableList(resultMap.constructorResultMappings);
       resultMap.propertyResultMappings = Collections.unmodifiableList(resultMap.propertyResultMappings);
       resultMap.mappedColumns = Collections.unmodifiableSet(resultMap.mappedColumns);
-      return resultMap;
-    }
-
-    private List<String> argNamesOfMatchingConstructor(List<String> constructorArgNames) {
-      Constructor<?>[] constructors = resultMap.type.getDeclaredConstructors();
-      for (Constructor<?> constructor : constructors) {
-        Class<?>[] paramTypes = constructor.getParameterTypes();
-        if (constructorArgNames.size() == paramTypes.length) {
-          List<String> paramNames = getArgNames(constructor);
-          if (constructorArgNames.containsAll(paramNames)
-              && argTypesMatch(constructorArgNames, paramTypes, paramNames)) {
-            return paramNames;
-          }
-        }
-      }
-      return null;
-    }
-
-    private boolean argTypesMatch(final List<String> constructorArgNames, Class<?>[] paramTypes,
-        List<String> paramNames) {
-      for (int i = 0; i < constructorArgNames.size(); i++) {
-        Class<?> actualType = paramTypes[paramNames.indexOf(constructorArgNames.get(i))];
-        Class<?> specifiedType = resultMap.constructorResultMappings.get(i).getJavaType();
-        if (!actualType.equals(specifiedType)) {
-          if (log.isDebugEnabled()) {
-            log.debug("While building result map '" + resultMap.id + "', found a constructor with arg names "
-                + constructorArgNames + ", but the type of '" + constructorArgNames.get(i)
-                + "' did not match. Specified: [" + specifiedType.getName() + "] Declared: [" + actualType.getName()
-                + "]");
-          }
-          return false;
-        }
-      }
-      return true;
-    }
 
-    private List<String> getArgNames(Constructor<?> constructor) {
-      List<String> paramNames = new ArrayList<>();
-      List<String> actualParamNames = null;
-      final Annotation[][] paramAnnotations = constructor.getParameterAnnotations();
-      int paramCount = paramAnnotations.length;
-      for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
-        String name = null;
-        for (Annotation annotation : paramAnnotations[paramIndex]) {
-          if (annotation instanceof Param) {
-            name = ((Param) annotation).value();
-            break;
-          }
-        }
-        if (name == null && resultMap.configuration.isUseActualParamName()) {
-          if (actualParamNames == null) {
-            actualParamNames = ParamNameUtil.getParamNames(constructor);
-          }
-          if (actualParamNames.size() > paramIndex) {
-            name = actualParamNames.get(paramIndex);
-          }
-        }
-        paramNames.add(name != null ? name : "arg" + paramIndex);
-      }
-      return paramNames;
+      return resultMap;
     }
   }