我们在更新具有关联/链接的分离实体时遇到了一些困难。我们有一个与类别实体具有多对多关系的文章实体。

当通过表单向现有文章添加类别并提交时，我们会收到以下消息：

执行"INSERT INTO项目…"时发生异常。。。密钥的重复条目"测试"

这很奇怪，因为实体是一个现有的实体（带有id），为什么要使用insert？

由于文章实体是分离/序列化的，我们试图将其合并，这次我们没有收到任何错误，但没有将新的类别链接插入数据库。我们统计了合并前后的类别，发现合并时它们会重置为数据库状态，所以如果它最初有2个类别，我们添加了第三个类别，则合并前和合并后的计数分别为3和2。新类别也是一个仅包含类别id的分部实体。

这是代码：

    $connection->beginTransaction();
    try {
        // Manage model by doctrine if it's not.
        $modelState = $entityManager->getUnitOfWork()->getEntityState($model);
        if ($modelState !== UnitOfWork::STATE_MANAGED) {
            $model = $entityManager->merge($model); // Strips new categories.
        }
        $entityManager->persist($model);
        $entityManager->flush();
        $connection->commit();
    } catch ('Exception $e) {
        $connection->rollback();
    }

实体：

<entity name="Article" table="articles" repository-class="Doctrine'Repository'BaseRepository">
    <id name="id" type="integer" column="id">
        <generator strategy="IDENTITY"/>
    </id>
    <field name="title" type="string" column="title" length="50" nullable="true"/>
    <many-to-many field="categories" target-entity="ArticleCategory" inversed-by="articles">
        <cascade>
            <cascade-persist/>
        </cascade>
        <join-table name="article_category_links">
            <join-columns>
                <join-column name="article_id" referenced-column-name="id" on-delete="CASCADE"/>
            </join-columns>
            <inverse-join-columns>
                <join-column name="article_category_id" referenced-column-name="id" on-delete="CASCADE"/>
            </inverse-join-columns>
        </join-table>
    </many-to-many>
</entity>
<entity name="ArticleCategory" table="article_categories" repository-class="Doctrine'Repository'BaseRepository">
    <id name="id" type="integer" column="id">
        <generator strategy="IDENTITY"/>
    </id>
    <field name="name" type="string" column="name" length="200" nullable="true"/>
    <many-to-many field="articles" target-entity="Article" mapped-by="categories">
        <cascade>
            <cascade-persist/>
        </cascade>
    </many-to-many>
</entity>

更新

这就是我们正在做的：

1.表单$_POST数据，第三类是新的：

Array
(
    [id] => 1
    [title] => test
    [categories] => Array
        (
            [0] => Array
                (
                    [id] => 1
                )
            [1] => Array
                (
                    [id] => 2
                )
            [2] => Array
                (
                    [id] => 3
                )
        )
)

2.反序列化的文章（JMS''Serializer）：

Article Object
(
    [id:protected] => 1
    [title:protected] => test
    [categories:protected] => Array
        (
            [0] => ArticleCategory Object
                (
                    [id:protected] => 1
                    [name:protected] => 
                    [articles:protected] => 
                )
            [1] => ArticleCategory Object
                (
                    [id:protected] => 2
                    [name:protected] => 
                    [articles:protected] => 
                )
            [2] => ArticleCategory Object
                (
                    [id:protected] => 3
                    [name:protected] => 
                    [articles:protected] => 
                )
        )
)

3.合并分离/反序列化的项目，删除第三类

$article = $entityManager->merge($article);

4.Flush，更新所有文章数据，但没有链接到第三类，因为它被删除了

$entityManager->flush();

以下是更多示例/测试：

// With attached article and no merging.
// Creates the link to the article, but the category becomes a new one (new id)..
$article = $articleRepository->getById(1)->getItem();
$category = new ArticleCategory();
$category->setId(3); // This doesnt matter since it becomes a new one.
$article->addCategory($category);
$articleRepository->getEntityManager->flush();
// With attached article and merging of category.
// Creates the link to the article but it clears all the category fields..
$article = $articleRepository->getById(1)->getItem();
$category = new ArticleCategory();
$category->setId(3);
$category = $categoryRepository->getEntityManager->merge($category);
$article->addCategory($category);
$articleRepository->getEntityManager->flush();
// With detached and merged article.
// No links no errors, but other article fields gets updated.
$category = new ArticleCategory();
$category->setId(3);
$article->addCategory($category);
echo count($article->getCategories()); // 3
$article = $articleRepository->getEntityManager->merge($article);
echo count($article->getCategories()); // 2, the new one gets removed.
$articleRepository->getEntityManager->flush();

$model = $entityManager->merge($model);

$entityManager->persist($model);

$cat1 = $entityManager->find("ArticleCategory", 1);
$cat2 = $entityManager->find("ArticleCategory", 2);
$model = $entityManager->find("Article", $id);
$model->getCategories()->add($cat1);
$model->getCategories()->add($cat2);
// because the $model exists, you only need to syncronize the changes in the db
$entityManager->flush();

$detachedEntity = unserialize($model); // some detached entity
$entity = $entityManager->merge($detachedEntity);
// and then, sync the changes in db
$entityManager->flush();