Add option for allowing null value on foreach tag

Author: kazuki43zoo

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

@@ -268,6 +268,7 @@ private void settingsElement(Properties props) {
     configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
     configuration.setLogPrefix(props.getProperty("logPrefix"));
     configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
+    configuration.setNullableOnForEach(booleanValueOf(props.getProperty("nullableOnForEach"), false));
   }
 
   private void environmentsElement(XNode context) throws Exception {

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

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <!--
 
-       Copyright 2009-2018 the original author or authors.
+       Copyright 2009-2020 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.
@@ -271,6 +271,7 @@ suffixOverrides CDATA #IMPLIED
 <!ELEMENT foreach (#PCDATA | include | trim | where | set | foreach | choose | if | bind)*>
 <!ATTLIST foreach
 collection CDATA #REQUIRED
+nullable (true|false) #IMPLIED
 item CDATA #IMPLIED
 index CDATA #IMPLIED
 open CDATA #IMPLIED

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

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
 
-       Copyright 2009-2018 the original author or authors.
+       Copyright 2009-2020 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.
@@ -599,6 +599,7 @@
         <xs:element ref="bind"/>
       </xs:choice>
       <xs:attribute name="collection" use="required"/>
+      <xs:attribute name="nullable" type="xs:boolean"/>
       <xs:attribute name="item"/>
       <xs:attribute name="index"/>
       <xs:attribute name="open"/>

src/main/java/org/apache/ibatis/scripting/xmltags/ExpressionEvaluator.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2019 the original author or authors.
+ *    Copyright 2009-2020 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.
@@ -40,9 +40,20 @@ public boolean evaluateBoolean(String expression, Object parameterObject) {
   }
 
   public Iterable<?> evaluateIterable(String expression, Object parameterObject) {
+    return evaluateIterable(expression, parameterObject, false);
+  }
+
+  /**
+   * @since 3.5.5
+   */
+  public Iterable<?> evaluateIterable(String expression, Object parameterObject, boolean nullable) {
     Object value = OgnlCache.getValue(expression, parameterObject);
     if (value == null) {
-      throw new BuilderException("The expression '" + expression + "' evaluated to a null value.");
+      if (nullable) {
+        return null;
+      } else {
+        throw new BuilderException("The expression '" + expression + "' evaluated to a null value.");
+      }
     }
     if (value instanceof Iterable) {
       return (Iterable<?>) value;

src/main/java/org/apache/ibatis/scripting/xmltags/ForEachSqlNode.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2019 the original author or authors.
+ *    Copyright 2009-2020 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.
@@ -16,6 +16,7 @@
 package org.apache.ibatis.scripting.xmltags;
 
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.ibatis.parsing.GenericTokenParser;
 import org.apache.ibatis.session.Configuration;
@@ -28,6 +29,7 @@ public class ForEachSqlNode implements SqlNode {
 
   private final ExpressionEvaluator evaluator;
   private final String collectionExpression;
+  private final Boolean nullable;
   private final SqlNode contents;
   private final String open;
   private final String close;
@@ -36,9 +38,21 @@ public class ForEachSqlNode implements SqlNode {
   private final String index;
   private final Configuration configuration;
 
+  /**
+   * @deprecated Since 3.5.5, use the {@link #ForEachSqlNode(Configuration, SqlNode, String, Boolean, String, String, String, String, String)}.
+   */
+  @Deprecated
   public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, String index, String item, String open, String close, String separator) {
+    this(configuration, contents, collectionExpression, null, index, item, open, close, separator);
+  }
+
+  /**
+   * @since 3.5.5
+   */
+  public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, Boolean nullable, String index, String item, String open, String close, String separator) {
     this.evaluator = new ExpressionEvaluator();
     this.collectionExpression = collectionExpression;
+    this.nullable = nullable;
     this.contents = contents;
     this.open = open;
     this.close = close;
@@ -51,8 +65,9 @@ public ForEachSqlNode(Configuration configuration, SqlNode contents, String coll
   @Override
   public boolean apply(DynamicContext context) {
     Map<String, Object> bindings = context.getBindings();
-    final Iterable<?> iterable = evaluator.evaluateIterable(collectionExpression, bindings);
-    if (!iterable.iterator().hasNext()) {
+    final Iterable<?> iterable = evaluator.evaluateIterable(collectionExpression, bindings,
+      Optional.ofNullable(nullable).orElseGet(configuration::isNullableOnForEach));
+    if (iterable == null || !iterable.iterator().hasNext()) {
       return true;
     }
     boolean first = true;

src/main/java/org/apache/ibatis/scripting/xmltags/XMLScriptBuilder.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2019 the original author or authors.
+ *    Copyright 2009-2020 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.
@@ -171,12 +171,13 @@ public ForEachHandler() {
     public void handleNode(XNode nodeToHandle, List<SqlNode> targetContents) {
       MixedSqlNode mixedSqlNode = parseDynamicTags(nodeToHandle);
       String collection = nodeToHandle.getStringAttribute("collection");
+      Boolean nullable = nodeToHandle.getBooleanAttribute("nullable");
       String item = nodeToHandle.getStringAttribute("item");
       String index = nodeToHandle.getStringAttribute("index");
       String open = nodeToHandle.getStringAttribute("open");
       String close = nodeToHandle.getStringAttribute("close");
       String separator = nodeToHandle.getStringAttribute("separator");
-      ForEachSqlNode forEachSqlNode = new ForEachSqlNode(configuration, mixedSqlNode, collection, index, item, open, close, separator);
+      ForEachSqlNode forEachSqlNode = new ForEachSqlNode(configuration, mixedSqlNode, collection, nullable, index, item, open, close, separator);
       targetContents.add(forEachSqlNode);
     }
   }

src/main/java/org/apache/ibatis/session/Configuration.java

@@ -113,6 +113,7 @@ public class Configuration {
   protected boolean callSettersOnNulls;
   protected boolean useActualParamName = true;
   protected boolean returnInstanceForEmptyRow;
+  protected boolean nullableOnForEach;
 
   protected String logPrefix;
   protected Class<? extends Log> logImpl;
@@ -266,6 +267,28 @@ public void setReturnInstanceForEmptyRow(boolean returnEmptyInstance) {
     this.returnInstanceForEmptyRow = returnEmptyInstance;
   }
 
+  /**
+   * Sets the default value of 'nullable' attribute on 'foreach' tag.
+   *
+   * @param nullableOnForEach If nullable, set to {@code true}
+   * @since 3.5.5
+   */
+  public void setNullableOnForEach(boolean nullableOnForEach) {
+    this.nullableOnForEach = nullableOnForEach;
+  }
+
+  /**
+   * Returns the default value of of 'nullable' attribute on 'foreach' tag.
+   *
+   * <p>Default is {@code false}.
+   *
+   * @return If nullable, set to {@code true}
+   * @since 3.5.5
+   */
+  public boolean isNullableOnForEach() {
+    return nullableOnForEach;
+  }
+
   public String getDatabaseId() {
     return databaseId;
   }

src/test/java/org/apache/ibatis/builder/CustomizedSettingsMapperConfig.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <!--
 
-       Copyright 2009-2019 the original author or authors.
+       Copyright 2009-2020 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.
@@ -54,6 +54,7 @@
     <setting name="vfsImpl" value="org.apache.ibatis.io.JBoss6VFS"/>
     <setting name="configurationFactory" value="java.lang.String"/>
     <setting name="defaultEnumTypeHandler" value="org.apache.ibatis.type.EnumOrdinalTypeHandler"/>
+    <setting name="nullableOnForEach" value="true"/>
   </settings>
 
   <typeAliases>

src/test/java/org/apache/ibatis/builder/XmlConfigBuilderTest.java

@@ -100,6 +100,7 @@ void shouldSuccessfullyLoadMinimalXMLConfigFile() throws Exception {
       assertNull(config.getLogImpl());
       assertNull(config.getConfigurationFactory());
       assertThat(config.getTypeHandlerRegistry().getTypeHandler(RoundingMode.class)).isInstanceOf(EnumTypeHandler.class);
+      assertThat(config.isNullableOnForEach()).isFalse();
     }
   }
 
@@ -194,6 +195,7 @@ void shouldSuccessfullyLoadXMLConfigFile() throws Exception {
       assertThat(config.getLogImpl().getName()).isEqualTo(Slf4jImpl.class.getName());
       assertThat(config.getVfsImpl().getName()).isEqualTo(JBoss6VFS.class.getName());
       assertThat(config.getConfigurationFactory().getName()).isEqualTo(String.class.getName());
+      assertThat(config.isNullableOnForEach()).isTrue();
 
       assertThat(config.getTypeAliasRegistry().getTypeAliases().get("blogauthor")).isEqualTo(Author.class);
       assertThat(config.getTypeAliasRegistry().getTypeAliases().get("blog")).isEqualTo(Blog.class);

src/test/java/org/apache/ibatis/submitted/foreach/ForEachTest.java

@@ -18,7 +18,9 @@
 import static com.googlecode.catchexception.apis.BDDCatchException.*;
 import static org.assertj.core.api.BDDAssertions.then;
 
+import java.io.IOException;
 import java.io.Reader;
+import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -139,4 +141,76 @@ void shouldRemoveIndexVariableInTheContext() {
     }
   }
 
+  @Test
+  void shouldAllowNullWhenAttributeIsOmitAndConfigurationIsDefault() throws IOException, SQLException {
+    SqlSessionFactory sqlSessionFactory;
+    try (Reader reader = Resources.getResourceAsReader("org/apache/ibatis/submitted/foreach/mybatis-config.xml")) {
+      sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
+    }
+    BaseDataTest.runScript(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
+      "org/apache/ibatis/submitted/foreach/CreateDB.sql");
+
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      User user = new User();
+      user.setFriendList(null);
+      mapper.countUserWithNullableIsOmit(user);
+      Assertions.fail();
+    } catch (PersistenceException e) {
+      Assertions.assertEquals("The expression 'friendList' evaluated to a null value.", e.getCause().getMessage());
+    }
+  }
+
+  @Test
+  void shouldAllowNullWhenAttributeIsOmitAndConfigurationIsTrue() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      sqlSessionFactory.getConfiguration().setNullableOnForEach(true);
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      User user = new User();
+      user.setFriendList(null);
+      int result = mapper.countUserWithNullableIsOmit(user);
+      Assertions.assertEquals(6, result);
+    }
+  }
+
+  @Test
+  void shouldNotAllowNullWhenAttributeIsOmitAndConfigurationIsFalse() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      sqlSessionFactory.getConfiguration().setNullableOnForEach(false);
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      User user = new User();
+      user.setFriendList(null);
+      mapper.countUserWithNullableIsOmit(user);
+      Assertions.fail();
+    } catch (PersistenceException e) {
+      Assertions.assertEquals("The expression 'friendList' evaluated to a null value.", e.getCause().getMessage());
+    }
+  }
+
+  @Test
+  void shouldAllowNullWhenAttributeIsTrueAndConfigurationIsFalse() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      sqlSessionFactory.getConfiguration().setNullableOnForEach(false);
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      User user = new User();
+      user.setFriendList(null);
+      int result = mapper.countUserWithNullableIsTrue(user);
+      Assertions.assertEquals(6, result);
+    }
+  }
+
+  @Test
+  void shouldNotAllowNullWhenAttributeIsFalseAndConfigurationIsTrue() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      sqlSessionFactory.getConfiguration().setNullableOnForEach(true);
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      User user = new User();
+      user.setFriendList(null);
+      mapper.countUserWithNullableIsFalse(user);
+      Assertions.fail();
+    } catch (PersistenceException e) {
+      Assertions.assertEquals("The expression 'friendList' evaluated to a null value.", e.getCause().getMessage());
+    }
+  }
+
 }