#2641 - Provide a decent default toString() implementation for entity beans

ebean-api/src/main/java/io/ebean/bean/BeanCollection.java

@@ -18,7 +18,7 @@ import java.util.Set;
  * <em>java.util.Collection</em>. The reason being that java.util.Map is not a
  * Collection. I realise this makes this name confusing so I apologise for that.
  */
-public interface BeanCollection<E> extends Serializable {
+public interface BeanCollection<E> extends Serializable, ToStringAware {
 
   enum ModifyListenMode {
     /**

ebean-api/src/main/java/io/ebean/bean/EntityBean.java

@@ -11,7 +11,7 @@ import java.io.Serializable;
  * general application consumption.
  * </p>
  */
-public interface EntityBean extends Serializable {
+public interface EntityBean extends Serializable, ToStringAware {
 
   /**
    * Return all the property names in defined order.
@@ -109,4 +109,8 @@ public interface EntityBean extends Serializable {
     throw new NotEnhancedException();
   }
 
+  @Override
+  default void toString(ToStringBuilder builder) {
+    throw new NotEnhancedException();
+  }
 }

ebean-api/src/main/java/io/ebean/bean/ToStringAware.java

@@ -0,0 +1,12 @@
+package io.ebean.bean;
+
+/**
+ * A type that can participate in building toString content with ToStringBuilder.
+ */
+public interface ToStringAware {
+
+  /**
+   * Append to the ToStringBuilder.
+   */
+  void toString(ToStringBuilder builder);
+}

ebean-api/src/main/java/io/ebean/bean/ToStringBuilder.java

@@ -0,0 +1,153 @@
+package io.ebean.bean;
+
+import java.util.Collection;
+import java.util.IdentityHashMap;
+
+/**
+ * Helps build toString content taking into account recursion.
+ * <p>
+ * That is, it detects and handles the case where there are relationships that recurse
+ * and would otherwise become an infinite loop (e.g. bidirectional parent child).
+ */
+public final class ToStringBuilder {
+
+  /**
+   * The max number of objects that we allow before stopping content being appended.
+   */
+  private static final int MAX = 100;
+
+  /**
+   * Max length of content in string form added for any given value.
+   */
+  private static final int TRIM_LENGTH = 500;
+
+  /**
+   * The max total content after which we stop content being appended.
+   */
+  private static final int MAX_TOTAL_CONTENT = 2000;
+
+  private final IdentityHashMap<Object, Integer> id = new IdentityHashMap<>();
+  private final StringBuilder sb = new StringBuilder(50);
+  private boolean first = true;
+  private int counter;
+
+  @Override
+  public String toString() {
+    return sb.toString();
+  }
+
+  /**
+   * Set of an object being added.
+   */
+  public void start(Object bean) {
+    if (counter == 0) {
+      id.putIfAbsent(bean, 0);
+    }
+    if (counter <= MAX) {
+      sb.append(bean.getClass().getSimpleName()).append("@").append(counter).append("(");
+    }
+  }
+
+  /**
+   * Add a property as name value pair.
+   */
+  public void add(String name, Object value) {
+    if (value != null && counter <= MAX) {
+      key(name);
+      value(value);
+    }
+  }
+
+  /**
+   * Add raw content.
+   */
+  public void addRaw(String content) {
+    sb.append(content);
+  }
+
+  /**
+   * End of an object.
+   */
+  public void end() {
+    if (counter <= MAX) {
+      sb.append(")");
+    }
+  }
+
+  private void key(String name) {
+    if (counter > MAX) {
+      return;
+    }
+    if (first) {
+      first = false;
+    } else {
+      sb.append(", ");
+    }
+    sb.append(name).append(":");
+  }
+
+  private void value(Object value) {
+    if (counter > MAX) {
+      return;
+    }
+    if (value instanceof ToStringAware) {
+      if (push(value)) {
+        ((ToStringAware) value).toString(this);
+      }
+    } else if (value instanceof Collection) {
+      addCollection((Collection<?>) value);
+    } else {
+      String content = String.valueOf(value);
+      if (content.length() > TRIM_LENGTH) {
+        content = content.substring(0, TRIM_LENGTH) + " <trimmed>";
+      }
+      sb.append(content);
+      if (sb.length() >= MAX_TOTAL_CONTENT) {
+        sb.append(" ...");
+        counter += MAX;
+      }
+    }
+  }
+
+  /**
+   * Add a collection of values.
+   */
+  public void addCollection(Collection<?> c) {
+    if (c == null || c.isEmpty()) {
+      sb.append("[]");
+      return;
+    }
+    int collectionPos = 0;
+    sb.append("[");
+    for (Object o : c) {
+      if (collectionPos++ > 0) {
+        sb.append(", ");
+      }
+      value(o);
+      if (counter > MAX) {
+        return;
+      }
+    }
+    sb.append("]");
+  }
+
+  private boolean push(Object bean) {
+    if (counter > MAX) {
+      return false;
+    }
+    if (counter == MAX) {
+      sb.append(" ...");
+      counter++;
+      return false;
+    }
+    Integer idx = id.putIfAbsent(bean, counter++);
+    if (idx != null) {
+      --counter;
+      sb.append(bean.getClass().getSimpleName()).append("@").append(idx);
+      return false;
+    }
+    first = true;
+    return true;
+  }
+
+}

ebean-api/src/main/java/io/ebean/common/BeanList.java

@@ -1,9 +1,6 @@
 package io.ebean.common;
 
-import io.ebean.bean.BeanCollection;
-import io.ebean.bean.BeanCollectionAdd;
-import io.ebean.bean.BeanCollectionLoader;
-import io.ebean.bean.EntityBean;
+import io.ebean.bean.*;
 
 import java.io.Serializable;
 import java.util.ArrayList;
@@ -47,6 +44,11 @@ public final class BeanList<E> extends AbstractBeanCollection<E> implements List
     super(loader, ownerBean, propertyName);
   }
 
+  @Override
+  public void toString(ToStringBuilder builder) {
+    builder.addCollection(list);
+  }
+
   @Override
   public void reset(EntityBean ownerBean, String propertyName) {
     this.ownerBean = ownerBean;

ebean-api/src/main/java/io/ebean/common/BeanMap.java

@@ -3,6 +3,7 @@ package io.ebean.common;
 import io.ebean.bean.BeanCollection;
 import io.ebean.bean.BeanCollectionLoader;
 import io.ebean.bean.EntityBean;
+import io.ebean.bean.ToStringBuilder;
 
 import java.util.Collection;
 import java.util.Collections;
@@ -40,6 +41,19 @@ public final class BeanMap<K, E> extends AbstractBeanCollection<E> implements Ma
     super(ebeanServer, ownerBean, propertyName);
   }
 
+  @Override
+  public void toString(ToStringBuilder builder) {
+    if (map == null || map.isEmpty()) {
+      builder.addRaw("{}");
+    } else {
+      builder.addRaw("{");
+      for (Entry<K, E> entry : map.entrySet()) {
+        builder.add(String.valueOf(entry.getKey()), entry.getValue());
+      }
+      builder.addRaw("}");
+    }
+  }
+
   @Override
   public void reset(EntityBean ownerBean, String propertyName) {
     this.ownerBean = ownerBean;

ebean-api/src/main/java/io/ebean/common/BeanSet.java

@@ -1,9 +1,6 @@
 package io.ebean.common;
 
-import io.ebean.bean.BeanCollection;
-import io.ebean.bean.BeanCollectionAdd;
-import io.ebean.bean.BeanCollectionLoader;
-import io.ebean.bean.EntityBean;
+import io.ebean.bean.*;
 
 import java.io.Serializable;
 import java.util.Collection;
@@ -41,6 +38,11 @@ public final class BeanSet<E> extends AbstractBeanCollection<E> implements Set<E
     super(loader, ownerBean, propertyName);
   }
 
+  @Override
+  public void toString(ToStringBuilder builder) {
+    builder.addCollection(set);
+  }
+
   @Override
   public void reset(EntityBean ownerBean, String propertyName) {
     this.ownerBean = ownerBean;

ebean-api/src/test/java/io/ebean/bean/ToStringBuilderTest.java

@@ -0,0 +1,124 @@
+package io.ebean.bean;
+
+import io.ebean.common.BeanList;
+import io.ebean.common.BeanMap;
+import io.ebean.common.BeanSet;
+import org.junit.jupiter.api.Test;
+
+import java.util.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ToStringBuilderTest {
+
+  @Test
+  void basic() {
+    ToStringBuilder builder = new ToStringBuilder();
+    builder.start(new Object());
+    builder.end();
+    assertThat(builder.toString()).isEqualTo("Object@0()");
+  }
+
+  @Test
+  void fields() {
+    ToStringBuilder builder = new ToStringBuilder();
+    builder.start(new Object());
+    builder.add("a", 1);
+    builder.add("b", "B");
+    builder.end();
+    assertThat(builder.toString()).isEqualTo("Object@0(a:1, b:B)");
+  }
+
+  @Test
+  void flatBean() {
+    Recurse instance0 = new Recurse(42, "java");
+    assertThat(instance0.toString()).isEqualTo("Recurse@0(id:42, nm:java)");
+  }
+
+  @Test
+  void recursive_expect_reference() {
+    Recurse instance0 = new Recurse(42, "java");
+    instance0.other = instance0;
+
+    assertThat(instance0.toString()).isEqualTo("Recurse@0(id:42, nm:java, other:Recurse@0)");
+  }
+
+  @Test
+  void notRecursive() {
+    Recurse instance0 = new Recurse(42, "java");
+    instance0.other = new Recurse(43, "jvm");
+    assertThat(instance0.toString()).isEqualTo("Recurse@0(id:42, nm:java, other:Recurse@1(id:43, nm:jvm))");
+  }
+
+  @Test
+  void beanList_null_empty() {
+    assertThat(toStringFor(new BeanList<String>(null))).isEqualTo("[]");
+    assertThat(toStringFor(new BeanList<String>(Collections.emptyList()))).isEqualTo("[]");
+  }
+
+  @Test
+  void beanSet_null_empty() {
+    assertThat(toStringFor(new BeanSet<String>(null))).isEqualTo("[]");
+    assertThat(toStringFor(new BeanSet<String>(Collections.emptySet()))).isEqualTo("[]");
+  }
+
+  @Test
+  void beanMap_null_empty() {
+    assertThat(toStringFor(new BeanMap<String, String>(null))).isEqualTo("{}");
+    assertThat(toStringFor(new BeanMap<String, String>(Collections.emptyMap()))).isEqualTo("{}");
+  }
+
+  @Test
+  void beanList_some() {
+    BeanList<Recurse> list = new BeanList<>(List.of(new Recurse(1, "a"), new Recurse(2, "b")));
+    assertThat(toStringFor(list)).isEqualTo("[Recurse@1(id:1, nm:a), Recurse@2(id:2, nm:b)]");
+  }
+
+  @Test
+  void beanSet_some() {
+    BeanSet<Recurse> list = new BeanSet<>(new LinkedHashSet<>(List.of(new Recurse(1, "a"), new Recurse(2, "b"))));
+    assertThat(toStringFor(list)).isEqualTo("[Recurse@1(id:1, nm:a), Recurse@2(id:2, nm:b)]");
+  }
+
+  @Test
+  void beanMap_some() {
+    Map<String, Recurse> under = new LinkedHashMap<>();
+    under.put("a", new Recurse(1, "a"));
+    under.put("b", new Recurse(2, "b"));
+    BeanMap<String, Recurse> list = new BeanMap<>(under);
+    assertThat(toStringFor(list)).isEqualTo("{a:Recurse@1(id:1, nm:a), b:Recurse@2(id:2, nm:b)}");
+  }
+
+  private String toStringFor(ToStringAware aware) {
+    ToStringBuilder builder = new ToStringBuilder();
+    aware.toString(builder);
+    return builder.toString();
+  }
+
+  static class Recurse implements ToStringAware {
+
+    final int id;
+    final String nm;
+    Recurse other;
+
+    Recurse(int id, String nm) {
+      this.id = id;
+      this.nm = nm;
+    }
+
+    public String toString() {
+      ToStringBuilder builder = new ToStringBuilder();
+      toString(builder);
+      return builder.toString();
+    }
+
+    @Override
+    public void toString(ToStringBuilder builder) {
+      builder.start(this);
+      builder.add("id", id);
+      builder.add("nm", nm);
+      builder.add("other", other);
+      builder.end();
+    }
+  }
+}

ebean-core/src/main/resources/META-INF/ebean-version.mf

@@ -1 +1 @@
-ebean-version: 129
+ebean-version: 133