fixes #721 Allow specifying constructor arg by its parameter name.

src/main/java/org/apache/ibatis/annotations/Arg.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2017 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.
@@ -44,4 +44,6 @@
   String select() default "";
 
   String resultMap() default "";
+
+  String name() default "";
 }

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

@@ -592,7 +592,7 @@ private void applyConstructorArgs(Arg[] args, Class<?> resultType, List<ResultMa
               (arg.typeHandler() == UnknownTypeHandler.class ? null : arg.typeHandler());
       ResultMapping resultMapping = assistant.buildResultMapping(
           resultType,
-          null,
+          nullOrEmpty(arg.name()),
           nullOrEmpty(arg.column()),
           arg.javaType() == void.class ? null : arg.javaType(),
           arg.jdbcType() == JdbcType.UNDEFINED ? null : arg.jdbcType(),

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

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2017 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.
@@ -358,7 +358,12 @@ private boolean databaseIdMatchesCurrent(String id, String databaseId, String re
   }
 
   private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception {
-    String property = context.getStringAttribute("property");
+    String property;
+    if (flags.contains(ResultFlag.CONSTRUCTOR)) {
+      property = context.getStringAttribute("name");
+    } else {
+      property = context.getStringAttribute("property");
+    }
     String column = context.getStringAttribute("column");
     String javaType = context.getStringAttribute("javaType");
     String jdbcType = context.getStringAttribute("jdbcType");

src/main/java/org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <!--
 
-       Copyright 2009-2016 the original author or authors.
+       Copyright 2009-2017 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.
@@ -89,6 +89,7 @@ jdbcType CDATA #IMPLIED
 typeHandler CDATA #IMPLIED
 select CDATA #IMPLIED
 resultMap CDATA #IMPLIED
+name CDATA #IMPLIED
 >
 
 <!ELEMENT arg EMPTY>
@@ -99,6 +100,7 @@ jdbcType CDATA #IMPLIED
 typeHandler CDATA #IMPLIED
 select CDATA #IMPLIED
 resultMap CDATA #IMPLIED
+name CDATA #IMPLIED
 >
 
 <!ELEMENT collection (constructor?,id*,result*,association*,collection*, discriminator?)>

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

@@ -15,19 +15,30 @@
  */
 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.Comparator;
 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.Jdk;
+import org.apache.ibatis.reflection.ParamNameUtil;
 import org.apache.ibatis.session.Configuration;
 
 /**
  * @author Clinton Begin
  */
 public class ResultMap {
+  private Configuration configuration;
+
   private String id;
   private Class<?> type;
   private List<ResultMapping> resultMappings;
@@ -45,13 +56,16 @@ private ResultMap() {
   }
 
   public static class Builder {
+    private static final Log log = LogFactory.getLog(Builder.class);
+
     private ResultMap resultMap = new ResultMap();
 
     public Builder(Configuration configuration, String id, Class<?> type, List<ResultMapping> resultMappings) {
       this(configuration, id, type, resultMappings, null);
     }
 
     public Builder(Configuration configuration, String id, Class<?> type, List<ResultMapping> resultMappings, Boolean autoMapping) {
+      resultMap.configuration = configuration;
       resultMap.id = id;
       resultMap.type = type;
       resultMap.resultMappings = resultMappings;
@@ -76,6 +90,7 @@ public ResultMap build() {
       resultMap.idResultMappings = new ArrayList<ResultMapping>();
       resultMap.constructorResultMappings = new ArrayList<ResultMapping>();
       resultMap.propertyResultMappings = new ArrayList<ResultMapping>();
+      final List<String> constructorArgNames = new ArrayList<String>();
       for (ResultMapping resultMapping : resultMap.resultMappings) {
         resultMap.hasNestedQueries = resultMap.hasNestedQueries || resultMapping.getNestedQueryId() != null;
         resultMap.hasNestedResultMaps = resultMap.hasNestedResultMaps || (resultMapping.getNestedResultMapId() != null && resultMapping.getResultSet() == null);
@@ -96,6 +111,9 @@ public ResultMap build() {
         }
         if (resultMapping.getFlags().contains(ResultFlag.CONSTRUCTOR)) {
           resultMap.constructorResultMappings.add(resultMapping);
+          if (resultMapping.getProperty() != null) {
+            constructorArgNames.add(resultMapping.getProperty());
+          }
         } else {
           resultMap.propertyResultMappings.add(resultMapping);
         }
@@ -106,6 +124,13 @@ public ResultMap build() {
       if (resultMap.idResultMappings.isEmpty()) {
         resultMap.idResultMappings.addAll(resultMap.resultMappings);
       }
+      if (!constructorArgNames.isEmpty()) {
+        if (!sortConstructorResultMapping(constructorArgNames)) {
+          throw new BuilderException("Failed to find a constructor in '"
+              + resultMap.getType().getName() + "' by arg names " + constructorArgNames
+              + ". There might be more info in debug log.");
+        }
+      }
       // lock down collections
       resultMap.resultMappings = Collections.unmodifiableList(resultMap.resultMappings);
       resultMap.idResultMappings = Collections.unmodifiableList(resultMap.idResultMappings);
@@ -114,6 +139,72 @@ public ResultMap build() {
       resultMap.mappedColumns = Collections.unmodifiableSet(resultMap.mappedColumns);
       return resultMap;
     }
+
+    private boolean sortConstructorResultMapping(final List<String> constructorArgNames) {
+      Constructor<?>[] constructors = resultMap.type.getDeclaredConstructors();
+      // Search constructors by arg names and types.
+      for (Constructor<?> constructor : constructors) {
+        Class<?>[] paramTypes = constructor.getParameterTypes();
+        if (constructorArgNames.size() == paramTypes.length) {
+          final List<String> paramNames = getArgNames(constructor);
+          if (constructorArgNames.containsAll(paramNames)) {
+            if (!argTypesMatch(constructorArgNames, paramTypes, paramNames)) {
+              continue;
+            }
+            // Found a matching constructor.
+            Collections.sort(resultMap.constructorResultMappings, new Comparator<ResultMapping>() {
+              @Override
+              public int compare(ResultMapping o1, ResultMapping o2) {
+                int paramIdx1 = paramNames.indexOf(o1.getProperty());
+                int paramIdx2 = paramNames.indexOf(o2.getProperty());
+                return paramIdx1 - paramIdx2;
+              }
+            });
+            return true;
+          }
+        }
+      }
+      return false;
+    }
+
+    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("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) {
+      if (resultMap.configuration.isUseActualParamName() && Jdk.parameterExists) {
+        return ParamNameUtil.getParamNames(constructor);
+      } else {
+        List<String> paramNames = new ArrayList<String>();
+        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;
+            }
+          }
+          paramNames.add(name != null ? name : "arg" + paramIndex);
+        }
+        return paramNames;
+      }
+    }
   }
 
   public String getId() {

src/test/java/org/apache/ibatis/submitted/named_constructor_args/CreateDB.sql

@@ -0,0 +1,26 @@
+--
+--    Copyright 2009-2017 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.
+--    You may obtain a copy of the License at
+--
+--       http://www.apache.org/licenses/LICENSE-2.0
+--
+--    Unless required by applicable law or agreed to in writing, software
+--    distributed under the License is distributed on an "AS IS" BASIS,
+--    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+--    See the License for the specific language governing permissions and
+--    limitations under the License.
+--
+
+drop table users if exists;
+
+create table users (
+  id int,
+  name varchar(20),
+  team int
+);
+
+insert into users (id, name, team) values
+(1, 'User1', 99);

src/test/java/org/apache/ibatis/submitted/named_constructor_args/InvalidNamedConstructorArgsTest.java

@@ -0,0 +1,123 @@
+/**
+ *    Copyright 2009-2017 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.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.submitted.named_constructor_args;
+
+import static org.hamcrest.CoreMatchers.*;
+
+import java.io.Reader;
+import java.sql.Connection;
+
+import org.apache.ibatis.annotations.Arg;
+import org.apache.ibatis.annotations.ConstructorArgs;
+import org.apache.ibatis.annotations.Select;
+import org.apache.ibatis.builder.BuilderException;
+import org.apache.ibatis.io.Resources;
+import org.apache.ibatis.jdbc.ScriptRunner;
+import org.apache.ibatis.session.Configuration;
+import org.apache.ibatis.session.SqlSession;
+import org.apache.ibatis.session.SqlSessionFactory;
+import org.apache.ibatis.session.SqlSessionFactoryBuilder;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+public class InvalidNamedConstructorArgsTest {
+  @Rule
+  public ExpectedException ex = ExpectedException.none();
+
+  private static SqlSessionFactory sqlSessionFactory;
+
+  @BeforeClass
+  public static void setUp() throws Exception {
+    // create an SqlSessionFactory
+    Reader reader = Resources.getResourceAsReader(
+        "org/apache/ibatis/submitted/named_constructor_args/mybatis-config.xml");
+    sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
+    reader.close();
+
+    // populate in-memory database
+    SqlSession session = sqlSessionFactory.openSession();
+    Connection conn = session.getConnection();
+    reader = Resources
+        .getResourceAsReader("org/apache/ibatis/submitted/named_constructor_args/CreateDB.sql");
+    ScriptRunner runner = new ScriptRunner(conn);
+    runner.setLogWriter(null);
+    runner.runScript(reader);
+    reader.close();
+    session.close();
+  }
+
+  interface NoMatchingConstructorMapper {
+    @ConstructorArgs({
+        @Arg(column = "id", name = "noSuchConstructorArg"),
+    })
+    @Select("select * from users ")
+    User select();
+  }
+
+  @Test
+  public void noMatchingConstructorArgName() {
+    ex.expect(BuilderException.class);
+    ex.expectMessage(startsWith("Failed to find a constructor in "
+        + "'org.apache.ibatis.submitted.named_constructor_args.User' by arg names [noSuchConstructorArg]."));
+
+    Configuration configuration = sqlSessionFactory.getConfiguration();
+    configuration.addMapper(NoMatchingConstructorMapper.class);
+  }
+
+  interface ConstructorWithWrongJavaType {
+    // There is a constructor with arg name 'id', but
+    // its type is different from the specified javaType.
+    @ConstructorArgs({
+        @Arg(column = "id", name = "id", javaType = Integer.class),
+    })
+    @Select("select * from users ")
+    User select();
+  }
+
+  @Test
+  public void wrongJavaType() {
+    ex.expect(BuilderException.class);
+    ex.expectMessage(startsWith("Failed to find a constructor in "
+        + "'org.apache.ibatis.submitted.named_constructor_args.User' by arg names [id]."));
+
+    Configuration configuration = sqlSessionFactory.getConfiguration();
+    configuration.addMapper(ConstructorWithWrongJavaType.class);
+  }
+
+  interface ConstructorMissingRequiresJavaType {
+    // There is a constructor with arg name 'id', but its type
+    // is different from the type of a property with the same name.
+    // javaType is required in this case.
+    // Debug log shows the detail of the matching error.
+    @ConstructorArgs({
+        @Arg(column = "id", name = "id"),
+    })
+    @Select("select * from users ")
+    User select();
+  }
+
+  @Test
+  public void missingRequiredJavaType() {
+    ex.expect(BuilderException.class);
+    ex.expectMessage(startsWith("Failed to find a constructor in "
+        + "'org.apache.ibatis.submitted.named_constructor_args.User' by arg names [id]."));
+
+    Configuration configuration = sqlSessionFactory.getConfiguration();
+    configuration.addMapper(ConstructorMissingRequiresJavaType.class);
+  }
+}