NEW: PersistVisitor

ebean-api/src/main/java/io/ebean/DB.java

@@ -477,6 +477,19 @@ public final class DB {
   public static int saveAll(Object... beans) throws OptimisticLockException {
     return getDefault().saveAll(beans);
   }
+  
+  /**
+   * This will visit all beans in the persist graph on a given object
+   * <code>start</code>. It will call the visitor for each dirty bean that would
+   * be saved with {@link #save(Object)} or {@link #saveAll(Collection)}. You can
+   * use this method to implement custom validations.
+   * 
+   * @param start   could be a bean, a list of beans or a map of beans.
+   * @param visitor the visitor
+   */
+  public static void visitSave(Object start, PersistVisitor visitor) {
+    getDefault().visitSave(start, visitor);
+  }
 
   /**
    * This method checks the uniqueness of a bean. I.e. if the save will work. It will return the

ebean-api/src/main/java/io/ebean/Database.java

@@ -1017,6 +1017,17 @@ public interface Database {
    * Save all the beans.
    */
   int saveAll(Object... beans) throws OptimisticLockException;
+  
+  /**
+   * This will visit all beans in the persist graph on a given object
+   * <code>start</code>. It will call the visitor for each dirty bean that would
+   * be saved with {@link #save(Object)} or {@link #saveAll(Collection)}. You can
+   * use this method to implement custom validations.
+   * 
+   * @param start   could be a bean, a list of beans or a map of beans.
+   * @param visitor the visitor
+   */
+  void visitSave(Object start, PersistVisitor visitor);
 
   /**
    * Delete the bean.

ebean-api/src/main/java/io/ebean/PersistVisitor.java

@@ -0,0 +1,29 @@
+package io.ebean;
+
+import java.util.Collection;
+import java.util.Map;
+
+import io.ebean.bean.EntityBean;
+import io.ebean.plugin.Property;
+
+@FunctionalInterface
+public interface PersistVisitor {
+
+  PersistVisitor visitBean(EntityBean bean);
+
+  default PersistVisitor visitProperty(Property prop) {
+    return this;
+  };
+
+  default PersistVisitor visitCollection(Collection<?> collection) {
+    return this;
+  };
+
+  default PersistVisitor visitMap(Map<?, ?> map) {
+    return this;
+  };
+
+  default void visitEnd() {
+  }
+
+}

ebean-core/src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -18,6 +18,7 @@ import io.ebean.FutureRowCount;
 import io.ebean.MergeOptions;
 import io.ebean.MergeOptionsBuilder;
 import io.ebean.PagedList;
+import io.ebean.PersistVisitor;
 import io.ebean.PersistenceContextScope;
 import io.ebean.ProfileLocation;
 import io.ebean.Query;
@@ -1628,6 +1629,11 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     persister.save(checkEntityBean(bean), transaction);
   }
 
+  @Override
+  public void visitSave(Object start, PersistVisitor visitor) {
+    new VisitHandler(descriptorManager).visit(start, visitor);
+  }
+
   @Override
   public void markAsDirty(Object bean) {
     if (!(bean instanceof EntityBean)) {

ebean-core/src/main/java/io/ebeaninternal/server/core/VisitHandler.java

@@ -0,0 +1,121 @@
+package io.ebeaninternal.server.core;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.Set;
+
+import io.ebean.PersistVisitor;
+import io.ebean.bean.EntityBean;
+import io.ebean.bean.EntityBeanIntercept;
+import io.ebeaninternal.server.deploy.BeanDescriptor;
+import io.ebeaninternal.server.deploy.BeanDescriptorManager;
+import io.ebeaninternal.server.deploy.BeanPropertyAssocMany;
+import io.ebeaninternal.server.deploy.BeanPropertyAssocOne;
+
+/**
+ * Handler to process persist graphs. It will allow you to visit a persist
+ * action (insert/update) and get information about all beans that will be
+ * affected by that action. This allows you to do validation and other things on
+ * a set of beans.
+ * 
+ * @author Roland Praml, FOCONIS AG
+ *
+ */
+class VisitHandler {
+
+  private final Set<Object> seen = Collections.newSetFromMap(new IdentityHashMap<Object, Boolean>());
+  private final BeanDescriptorManager beanDescriptorManager;
+
+  public VisitHandler(BeanDescriptorManager beanDescriptorManager) {
+    this.beanDescriptorManager = beanDescriptorManager;
+  }
+
+  public void visit(Object start, PersistVisitor visitor) {
+    if (start != null) {
+      if (start instanceof EntityBean) {
+        visitBean((EntityBean) start, visitor);
+      } else {
+        visitMany(start, visitor);
+      }
+    }
+    visitor.visitEnd();
+  }
+
+  private void visitBean(EntityBean bean, PersistVisitor visitor) {
+    if (!seen.add(bean)) {
+      return;
+    }
+    visitor = visitor.visitBean(bean);
+    if (visitor != null) {
+      BeanDescriptor<?> desc = beanDescriptorManager.descriptor(bean.getClass());
+      visitOnes(bean, visitor, desc, desc.propertiesOneImportedSave());
+      visitOnes(bean, visitor, desc, desc.propertiesOneExportedSave());
+      visitManys(bean, visitor, desc, desc.propertiesManySave());
+      visitor.visitEnd();
+    }
+  }
+
+  private void visitManys(EntityBean bean, PersistVisitor visitor, BeanDescriptor<?> desc,
+      BeanPropertyAssocMany<?>[] manys) {
+    EntityBeanIntercept ebi = bean._ebean_getIntercept();
+    for (BeanPropertyAssocMany<?> many : manys) {
+      // check that property is loaded and collection should be cascaded to
+      if (ebi.isLoadedProperty(many.propertyIndex()) && !many.isSkipSaveBeanCollection(bean, ebi.isNew())) {
+        Object manyValue = many.getValue(bean);
+        if (manyValue != null) {
+          PersistVisitor propertyVisitor = visitor.visitProperty(many);
+          if (propertyVisitor != null) {
+            visitMany(manyValue, propertyVisitor);
+            propertyVisitor.visitEnd();
+          }
+        }
+      }
+    }
+  }
+
+  private void visitMany(Object many, PersistVisitor visitor) {
+    if (!seen.add(many)) {
+      return;
+    }
+    if (many instanceof Collection) {
+      Collection<?> coll = (Collection<?>) many;
+      PersistVisitor collectionVisitor = visitor.visitCollection(coll);
+      if (collectionVisitor != null) {
+        for (Object elem : coll) {
+          visitBean((EntityBean) elem, collectionVisitor);
+        }
+        collectionVisitor.visitEnd();
+      }
+    } else if (many instanceof Map) {
+      Map<?, ?> map = (Map<?, ?>) many;
+      PersistVisitor mapVisitor = visitor.visitMap(map);
+      if (mapVisitor != null) {
+        for (Object elem : ((Map<?, ?>) many).values()) {
+          visitBean((EntityBean) elem, mapVisitor);
+        }
+        mapVisitor.visitEnd();
+      }
+    } else {
+      throw new IllegalArgumentException("Object " + many + " cannot be visited in persist graph");
+    }
+  }
+
+  private void visitOnes(EntityBean bean, PersistVisitor visitor, BeanDescriptor<?> desc,
+      BeanPropertyAssocOne<?>[] ones) {
+    EntityBeanIntercept ebi = bean._ebean_getIntercept();
+    for (BeanPropertyAssocOne<?> prop : ones) {
+      if (ebi.isLoadedProperty(prop.propertyIndex())) {
+        EntityBean detailBean = prop.getValueAsEntityBean(bean);
+        if (detailBean != null && !prop.isSaveRecurseSkippable(detailBean) && !prop.isReference(detailBean)) {
+          PersistVisitor propertyVisitor = visitor.visitProperty(prop);
+          if (propertyVisitor != null) {
+            visitBean(detailBean, propertyVisitor);
+            propertyVisitor.visitEnd();
+          }
+        }
+      }
+    }
+  }
+}

ebean-test/src/test/java/io/ebeaninternal/api/TDSpiServer.java

@@ -293,6 +293,11 @@ public class TDSpiServer implements SpiServer {
     return 0;
   }
 
+  @Override
+  public void visitSave(Object start, PersistVisitor visitor) {
+
+  }
+
   @Override
   public boolean delete(Object bean) throws OptimisticLockException {
     return false;

ebean-test/src/test/java/org/tests/basic/TPersistVisitor.java

@@ -0,0 +1,69 @@
+package org.tests.basic;
+
+import java.util.Collection;
+
+import io.ebean.DB;
+import io.ebean.PersistVisitor;
+import io.ebean.bean.EntityBean;
+import io.ebean.plugin.Property;
+/**
+ * Sample persist visitor that converts the visited beans in a XML-like structure
+ */
+public class TPersistVisitor implements PersistVisitor {
+
+    private final StringBuilder sb;
+    private final String indent;
+    private final String tag;
+    private boolean empty = true;
+    
+    public TPersistVisitor() {
+      this(new StringBuilder(), "", "root"); 
+    }
+    private TPersistVisitor(StringBuilder sb, String indent, String tag) {
+      this.sb = sb;
+      this.indent = indent;
+      this.tag = tag;
+      this.sb.append(indent).append('<').append(tag);
+    }
+    
+    TPersistVisitor newVisitor(String tag) {
+      if (empty) {
+        sb.append(">\n");
+        empty = false;
+      }
+      return new TPersistVisitor(sb, indent + "  ", tag);
+    }
+
+    @Override
+    public void visitEnd() {
+      if (empty) {
+        sb.append("/>\n");
+      } else {
+        this.sb.append(indent).append("</").append(tag).append(">\n");
+      }
+    }
+    
+    TPersistVisitor attr(String attr, Object value) {
+      sb.append(' ').append(attr).append('=').append('\'').append(value).append('\'');
+      return this;
+    }
+    
+    public TPersistVisitor visitBean(EntityBean bean) {
+      return newVisitor("bean").attr("type", bean.getClass().getSimpleName()).attr("newOrDirty", DB.beanState(bean).isNewOrDirty());
+    }
+
+    @Override
+    public PersistVisitor visitProperty(Property prop) {
+      return newVisitor("property").attr("name", prop.name());
+    }
+
+   @Override
+  public PersistVisitor visitCollection(Collection<?> collection) {
+     return newVisitor("collection").attr("size", collection.size());
+    }
+    
+    @Override
+    public String toString() {
+      return sb.toString();
+    }
+  }

ebean-test/src/test/java/org/tests/basic/TestM2MCascadeOne.java

@@ -3,12 +3,15 @@ package org.tests.basic;
 import io.ebean.BaseTestCase;
 import io.ebean.DB;
 import io.ebean.Query;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
 import org.junit.jupiter.api.Test;
 import org.tests.model.basic.MRole;
 import org.tests.model.basic.MUser;
 
 public class TestM2MCascadeOne extends BaseTestCase {
-
+  
   @Test
   public void test() {
 
@@ -30,8 +33,31 @@ public class TestM2MCascadeOne extends BaseTestCase {
     u1.addRole(r0);
     u1.addRole(r1);
 
+    TPersistVisitor tv = new TPersistVisitor();
+    DB.visitSave(u1, tv);
+    assertThat(tv.toString()).isEqualTo("<root>\n"
+        + "  <bean type='MUser' newOrDirty='false'>\n"
+        + "    <property name='roles'>\n"
+        + "      <collection size='2'>\n"
+        + "        <bean type='MRole' newOrDirty='false'/>\n"
+        + "        <bean type='MRole' newOrDirty='true'/>\n"
+        + "      </collection>\n"
+        + "    </property>\n"
+        + "  </bean>\n"
+        + "</root>\n");
+    
     DB.save(u1);
-
+    
+    u1 = DB.find(MUser.class, u.getUserid());
+    
+    tv = new TPersistVisitor();
+    DB.visitSave(u1, tv);
+    // collection is unloaded
+    assertThat(tv.toString()).isEqualTo("<root>\n"
+        + "  <bean type='MUser' newOrDirty='false'/>\n"
+        + "</root>\n");
+    
+    
   }
 
   @Test