Allow omit a 'method' attribute on SqlProvider annotation

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

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2019 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.
@@ -28,7 +28,33 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public @interface DeleteProvider {
+
+  /**
+   * Specify a type that implements an SQL provider method.
+   *
+   * @return a type that implements an SQL provider method
+   */
   Class<?> type();
 
-  String method();
+  /**
+   * Specify a method for providing an SQL.
+   *
+   * <p>
+   * Since 3.5.1, this attribute can omit.
+   * If this attribute omit, the MyBatis will call a method that decide by following rules.
+   * <ul>
+   *   <li>
+   *     If class that specified the {@link #type()} attribute implements the {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver},
+   *     the MyBatis use a method that returned by it
+   *   </li>
+   *   <li>
+   *     If cannot resolve a method by {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver}(= not implement it or it was returned {@code null}),
+   *     the MyBatis will search and use a fallback method that named {@code provideSql} from specified type
+   *   </li>
+   * </ul>
+   *
+   * @return a method name of method for providing an SQL
+   */
+  String method() default "";
+
 }

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

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2019 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.
@@ -28,7 +28,33 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public @interface InsertProvider {
+
+  /**
+   * Specify a type that implements an SQL provider method.
+   *
+   * @return a type that implements an SQL provider method
+   */
   Class<?> type();
 
-  String method();
+  /**
+   * Specify a method for providing an SQL.
+   *
+   * <p>
+   * Since 3.5.1, this attribute can omit.
+   * If this attribute omit, the MyBatis will call a method that decide by following rules.
+   * <ul>
+   *   <li>
+   *     If class that specified the {@link #type()} attribute implements the {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver},
+   *     the MyBatis use a method that returned by it
+   *   </li>
+   *   <li>
+   *     If cannot resolve a method by {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver}(= not implement it or it was returned {@code null}),
+   *     the MyBatis will search and use a fallback method that named {@code provideSql} from specified type
+   *   </li>
+   * </ul>
+   *
+   * @return a method name of method for providing an SQL
+   */
+  String method() default "";
+
 }

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

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2019 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.
@@ -28,7 +28,33 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public @interface SelectProvider {
+
+  /**
+   * Specify a type that implements an SQL provider method.
+   *
+   * @return a type that implements an SQL provider method
+   */
   Class<?> type();
 
-  String method();
+  /**
+   * Specify a method for providing an SQL.
+   *
+   * <p>
+   * Since 3.5.1, this attribute can omit.
+   * If this attribute omit, the MyBatis will call a method that decide by following rules.
+   * <ul>
+   *   <li>
+   *     If class that specified the {@link #type()} attribute implements the {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver},
+   *     the MyBatis use a method that returned by it
+   *   </li>
+   *   <li>
+   *     If cannot resolve a method by {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver}(= not implement it or it was returned {@code null}),
+   *     the MyBatis will search and use a fallback method that named {@code provideSql} from specified type
+   *   </li>
+   * </ul>
+   *
+   * @return a method name of method for providing an SQL
+   */
+  String method() default "";
+
 }

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

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2016 the original author or authors.
+ *    Copyright 2009-2019 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.
@@ -28,7 +28,33 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public @interface UpdateProvider {
+
+  /**
+   * Specify a type that implements an SQL provider method.
+   *
+   * @return a type that implements an SQL provider method
+   */
   Class<?> type();
 
-  String method();
+  /**
+   * Specify a method for providing an SQL.
+   *
+   * <p>
+   * Since 3.5.1, this attribute can omit.
+   * If this attribute omit, the MyBatis will call a method that decide by following rules.
+   * <ul>
+   *   <li>
+   *     If class that specified the {@link #type()} attribute implements the {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver},
+   *     the MyBatis use a method that returned by it
+   *   </li>
+   *   <li>
+   *     If cannot resolve a method by {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver}(= not implement it or it was returned {@code null}),
+   *     the MyBatis will search and use a fallback method that named {@code provideSql} from specified type
+   *   </li>
+   * </ul>
+   *
+   * @return a method name of method for providing an SQL
+   */
+  String method() default "";
+
 }

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

@@ -0,0 +1,75 @@
+/**
+ *    Copyright 2009-2019 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.builder.annotation;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.apache.ibatis.builder.BuilderException;
+
+/**
+ * The interface that resolve an SQL provider method via an SQL provider class.
+ *
+ * <p> This interface need to implements at an SQL provider class and
+ * it need to define the default constructor for creating a new instance.
+ *
+ * @since 3.5.1
+ * @author Kazuki Shimizu
+ */
+public interface ProviderMethodResolver {
+
+  /**
+   * Resolve an SQL provider method.
+   *
+   * <p> The default implementation return a method that matches following conditions.
+   * <ul>
+   *   <li>Method name matches with mapper method</li>
+   *   <li>Return type matches the {@link CharSequence}({@link String}, {@link StringBuilder}, etc...)</li>
+   * </ul>
+   * If matched method is zero or multiple, it throws a {@link BuilderException}.
+   *
+   * @param context a context for SQL provider
+   * @return an SQL provider method
+   * @throws BuilderException Throws when cannot resolve a target method
+   */
+  default Method resolveMethod(ProviderContext context) {
+    List<Method> sameNameMethods = Arrays.stream(getClass().getMethods())
+        .filter(m -> m.getName().equals(context.getMapperMethod().getName()))
+        .collect(Collectors.toList());
+    if (sameNameMethods.isEmpty()) {
+      throw new BuilderException("Cannot resolve the provider method because '"
+          + context.getMapperMethod().getName() + "' not found in SqlProvider '" + getClass().getName() + "'.");
+    }
+    List<Method> targetMethods = sameNameMethods.stream()
+        .filter(m -> CharSequence.class.isAssignableFrom(m.getReturnType()))
+        .collect(Collectors.toList());
+    if (targetMethods.size() == 1) {
+      return targetMethods.get(0);
+    }
+    if (targetMethods.isEmpty()) {
+      throw new BuilderException("Cannot resolve the provider method because '"
+          + context.getMapperMethod().getName() + "' does not return the CharSequence or its subclass in SqlProvider '"
+          + getClass().getName() + "'.");
+    } else {
+      throw new BuilderException("Cannot resolve the provider method because '"
+          + context.getMapperMethod().getName() + "' is found multiple in SqlProvider '" + getClass().getName() + "'.");
+    }
+  }
+
+}

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

@@ -62,16 +62,21 @@ public ProviderSqlSource(Configuration configuration, Object provider, Class<?>
       this.providerType = (Class<?>) provider.getClass().getMethod("type").invoke(provider);
       providerMethodName = (String) provider.getClass().getMethod("method").invoke(provider);
 
-      for (Method m : this.providerType.getMethods()) {
-        if (providerMethodName.equals(m.getName()) && CharSequence.class.isAssignableFrom(m.getReturnType())) {
-          if (providerMethod != null) {
-            throw new BuilderException("Error creating SqlSource for SqlProvider. Method '"
-                    + providerMethodName + "' is found multiple in SqlProvider '" + this.providerType.getName()
-                    + "'. Sql provider method can not overload.");
+      if (providerMethodName.length() == 0 && ProviderMethodResolver.class.isAssignableFrom(this.providerType)) {
+        this.providerMethod = ((ProviderMethodResolver) this.providerType.getDeclaredConstructor().newInstance())
+            .resolveMethod(new ProviderContext(mapperType, mapperMethod));
+      }
+      if (this.providerMethod == null) {
+        providerMethodName = providerMethodName.length() == 0 ? "provideSql" : providerMethodName;
+        for (Method m : this.providerType.getMethods()) {
+          if (providerMethodName.equals(m.getName()) && CharSequence.class.isAssignableFrom(m.getReturnType())) {
+            if (this.providerMethod != null) {
+              throw new BuilderException("Error creating SqlSource for SqlProvider. Method '"
+                  + providerMethodName + "' is found multiple in SqlProvider '" + this.providerType.getName()
+                  + "'. Sql provider method can not overload.");
+            }
+            this.providerMethod = m;
           }
-          this.providerMethod = m;
-          this.providerMethodArgumentNames = new ParamNameResolver(configuration, m).getNames();
-          this.providerMethodParameterTypes = m.getParameterTypes();
         }
       }
     } catch (BuilderException e) {
@@ -83,6 +88,8 @@ public ProviderSqlSource(Configuration configuration, Object provider, Class<?>
       throw new BuilderException("Error creating SqlSource for SqlProvider. Method '"
           + providerMethodName + "' not found in SqlProvider '" + this.providerType.getName() + "'.");
     }
+    this.providerMethodArgumentNames = new ParamNameResolver(configuration, this.providerMethod).getNames();
+    this.providerMethodParameterTypes = this.providerMethod.getParameterTypes();
     for (int i = 0; i < this.providerMethodParameterTypes.length; i++) {
       Class<?> parameterType = this.providerMethodParameterTypes[i];
       if (parameterType == ProviderContext.class) {

src/site/es/xdoc/java-api.xml

@@ -464,7 +464,13 @@ try (SqlSession session = sqlSessionFactory.openSession()) {
         </td>
         <td>Estas anotaciones SQL alternativas te permiten especificar un nombre de clases y un método que devolverán la SQL que debe ejecutarse (Since 3.4.6, you can specify the <code>CharSequence</code> instead of <code>String</code> as a method return type).
           Cuando se ejecute el método MyBatis instanciará la clase y ejecutará el método especificados en el provider. You can pass objects that passed to arguments of a mapper method, "Mapper interface type" and "Mapper method"
-          via the <code>ProviderContext</code>(available since MyBatis 3.4.5 or later) as method argument.(In MyBatis 3.4 or later, it's allow multiple parameters) Atributos: type, method.  El atributo type es el nombre completamente cualificado de una clase. El method es el nombre un método de dicha clase. Nota: A continuación hay una sección sobre la clase, que puede ayudar a construir SQL dinámico de una forma más clara y sencilla de leer.</td>
+          via the <code>ProviderContext</code>(available since MyBatis 3.4.5 or later) as method argument.(In MyBatis 3.4 or later, it's allow multiple parameters)
+          Atributos: type, method.  El atributo type es el nombre completamente cualificado de una clase.
+          El method es el nombre un método de dicha clase
+          (Since 3.5.1, you can omit <code>method</code> attribute, the MyBatis will resolve a target method via the
+          <code>ProviderMethodResolver</code> interface.
+          If not resolve by it, the MyBatis use the reserved fallback method that named <code>provideSql</code>).
+          Nota: A continuación hay una sección sobre la clase, que puede ayudar a construir SQL dinámico de una forma más clara y sencilla de leer.</td>
       </tr>
       <tr>
         <td><code>@Param</code></td>
@@ -583,6 +589,44 @@ class UserSqlBuilder {
   }
 }]]></source>
 
+    <p>This example shows usage the default implementation of <code>ProviderMethodResolver</code>(available since MyBatis 3.5.1 or later):</p>
+    <source><![CDATA[@SelectProvider(type = UserSqlProvider.class)
+List<User> getUsersByName(String name);
+
+// Implements the ProviderMethodResolver on your provider class
+class UserSqlProvider implements ProviderMethodResolver {
+  // In default implementation, it will resolve a method that method name is matched with mapper method
+  public static String getUsersByName(final String name) {
+    return new SQL(){{
+      SELECT("*");
+      FROM("users");
+      if (name != null) {
+        WHERE("name like #{value} || '%'");
+      }
+      ORDER_BY("id");
+    }}.toString();
+  }
+}]]></source>
+
+    <p>This example shows usage the default implementation of <code>ProviderMethodResolver</code>(available since MyBatis 3.5.1 or later):</p>
+    <source><![CDATA[@SelectProvider(type = UserSqlProvider.class)
+List<User> getUsersByName(String name);
+
+// Implements the ProviderMethodResolver on your provider class
+class UserSqlProvider implements ProviderMethodResolver {
+  // In default implementation, it will resolve a method that method name is matched with mapper method
+  public static String getUsersByName(final String name) {
+    return new SQL(){{
+      SELECT("*");
+      FROM("users");
+      if (name != null) {
+        WHERE("name like #{value} || '%'");
+      }
+      ORDER_BY("id");
+    }}.toString();
+  }
+}]]></source>
+
   </subsection>
 
   </section>

src/site/ja/xdoc/java-api.xml

@@ -477,7 +477,10 @@ try (SqlSession session = sqlSessionFactory.openSession()) {
         <td>これらのアノテーションは動的 SQL を生成するためのものです。実行時に指定されたメソッドが呼び出され、メソッドから返された SQL ステートメントが実行されます (MyBatis 3.4.6以降では、メソッドの返り値として <code>String</code> ではなく <code>CharSequence</code> を指定することができます)。
         マップドステートメントを実行する際、プロバイダーによって指定したクラスのインスタンスが作成され、指定されたメソッドが実行されます。
         なお、メソッド引数にはMapperメソッドの引数に渡したオブジェクトに加え、<code>ProviderContext</code>(MyBatis 3.4.5以降で利用可能)を介して「Mapperインタフェースの型」と「Mapperメソッド」を渡すことができます。(MyBatis 3.4以降では、複数の引数を渡すことができます)
-        キー: <code>type</code>, <code>method</code>. <code>type</code> にはクラスオブジェクト、<code>method</code> にはメソッド名を指定します。 <span class="label important">NOTE</span> 次の章で、クリーンで可読性の高いコードで動的 SQL を構築するためのクラスについて説明します。
+        キー: <code>type</code>, <code>method</code>. <code>type</code> にはクラスオブジェクト、<code>method</code> にはメソッド名を指定します
+        (MyBatis 3.5.1以降では、<code>method</code> 属性を省略することができます。その際MyBatisは、<code>ProviderMethodResolver</code> インタフェースを介して対象メソッドの解決を試み、
+        対象メソッドが解決できない場合は、<code>provideSql</code>という名前のメソッドを代替メソッドとして利用します)。
+        <span class="label important">NOTE</span> 次の章で、クリーンで可読性の高いコードで動的 SQL を構築するためのクラスについて説明します。
 </td>
       </tr>
       <tr>
@@ -591,6 +594,27 @@ class UserSqlBuilder {
       ORDER_BY(orderByColumn);
     }}.toString();
   }
+}]]></source>
+
+    <p>次のコードは、<code>ProviderMethodResolver</code>(MyBatis 3.5.1以降で利用可能)のデフォルト実装の利用例です。</p>
+    <source><![CDATA[@SelectProvider(type = UserSqlProvider.class)
+List<User> getUsersByName(String name);
+
+// SQLプロバイダクラスにProviderMethodResolverを実装する
+class UserSqlProvider implements ProviderMethodResolver {
+
+  // デフォルト実装では、マッパーメソッドと同名のメソッドが対象メソッドとして扱われます。
+  public static String getUsersByName(final String name) {
+    return new SQL(){{
+      SELECT("*");
+      FROM("users");
+      if (name != null) {
+        WHERE("name like #{value} || '%'");
+      }
+      ORDER_BY("id");
+    }}.toString();
+  }
+
 }]]></source>
 
   </subsection>