#365 - ENH: Add @DbComment with DDL generation of table and column comments

src/main/java/com/avaje/ebean/annotation/DbComment.java

@@ -0,0 +1,19 @@
+package com.avaje.ebean.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * A database table or column comment.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE})
+public @interface DbComment {
+
+  /**
+   * The database table or column comment.
+   */
+  String value();
+}

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/BaseTableDdl.java

@@ -21,6 +21,7 @@ import com.avaje.ebean.dbmigration.migration.DropTable;
 import com.avaje.ebean.dbmigration.migration.ForeignKey;
 import com.avaje.ebean.dbmigration.migration.UniqueConstraint;
 import com.avaje.ebean.dbmigration.model.MTable;
+import com.avaje.ebean.util.StringHelper;
 
 import java.io.IOException;
 import java.math.BigInteger;
@@ -123,7 +124,11 @@ public class BaseTableDdl implements TableDdl {
       writePrimaryKeyConstraint(apply, createTable.getPkName(), toColumnNames(pk));
     }
 
-    apply.newLine().append(")").endOfStatement();
+    apply.newLine().append(")");
+    addTableCommentInline(apply, createTable);
+    apply.endOfStatement();
+
+    addComments(apply, createTable);
 
     writeUniqueOneToOneConstraints(writer, createTable);
 
@@ -150,6 +155,37 @@ public class BaseTableDdl implements TableDdl {
 
   }
 
+  /**
+   * Add table and column comments (separate from the create table statement).
+   */
+  private void addComments(DdlBuffer apply, CreateTable createTable) throws IOException {
+    if (!platformDdl.isInlineComments()) {
+      String tableComment = createTable.getComment();
+      if (!StringHelper.isNull(tableComment)) {
+        platformDdl.addTableComment(apply, createTable.getName(), tableComment);
+      }
+
+      List<Column> columns = createTable.getColumn();
+      for (Column column : columns) {
+        if (!StringHelper.isNull(column.getComment())) {
+          platformDdl.addColumnComment(apply, createTable.getName(), column.getName(), column.getComment());
+        }
+      }
+    }
+  }
+
+  /**
+   * Add the table comment inline with the create table statement.
+   */
+  private void addTableCommentInline(DdlBuffer apply, CreateTable createTable) throws IOException {
+    if (platformDdl.isInlineComments()) {
+      String tableComment = createTable.getComment();
+      if (!StringHelper.isNull(tableComment)) {
+        platformDdl.inlineTableComment(apply, tableComment);
+      }
+    }
+  }
+
   private void writeTableColumns(DdlBuffer apply, List<Column> columns, boolean useIdentity) throws IOException {
     platformDdl.writeTableColumns(apply, columns, useIdentity);
   }

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/MySqlDdl.java

@@ -2,7 +2,12 @@ package com.avaje.ebean.dbmigration.ddlgeneration.platform;
 
 import com.avaje.ebean.config.dbplatform.DbIdentity;
 import com.avaje.ebean.config.dbplatform.DbTypeMap;
+import com.avaje.ebean.dbmigration.ddlgeneration.DdlBuffer;
 import com.avaje.ebean.dbmigration.migration.AlterColumn;
+import com.avaje.ebean.dbmigration.migration.Column;
+import com.avaje.ebeaninternal.server.lib.util.StringHelper;
+
+import java.io.IOException;
 
 /**
  * MySql specific DDL.
@@ -14,6 +19,7 @@ public class MySqlDdl extends PlatformDdl {
     this.alterColumn =  "modify";
     this.dropUniqueConstraint = "drop index";
     this.historyDdl = new MySqlHistoryDdl();
+    this.inlineComments = true;
   }
 
   /**
@@ -64,4 +70,26 @@ public class MySqlDdl extends PlatformDdl {
     // use modify
     return "alter table " + tableName + " modify " + columnName + " " + type + notnullClause;
   }
+
+  @Override
+  protected void writeColumnDefinition(DdlBuffer buffer, Column column, boolean useIdentity) throws IOException {
+    super.writeColumnDefinition(buffer, column, useIdentity);
+    String comment = column.getComment();
+    if (!StringHelper.isNull(comment)) {
+      // in mysql 5.5 column comment save in information_schema.COLUMNS.COLUMN_COMMENT(VARCHAR 1024)
+      if (comment.length() > 500) {
+        comment = comment.substring(0, 500);
+      }
+      buffer.append(String.format(" comment '%s'", comment));
+    }
+
+  }
+
+  public void inlineTableComment(DdlBuffer apply, String tableComment) throws IOException {
+    if (tableComment.length() > 1000) {
+      tableComment = tableComment.substring(0, 1000);
+    }
+    apply.append(" comment='").append(tableComment).append("'");
+  }
+
 }

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/PlatformDdl.java

@@ -37,6 +37,11 @@ public class PlatformDdl {
    */
   private final DbIdentity dbIdentity;
 
+  /**
+   * Set to true if table and column comments are included inline with the create statements.
+   */
+  protected boolean inlineComments;
+
   /**
    * Default assumes if exists is supported.
    */
@@ -116,6 +121,13 @@ public class PlatformDdl {
     return columnDefn + identitySuffix;
   }
 
+  /**
+   * Return true if the table and column comments are included inline.
+   */
+  public boolean isInlineComments() {
+    return inlineComments;
+  }
+
   /**
    * Write all the table columns converting to platform types as necessary.
    */
@@ -386,4 +398,27 @@ public class PlatformDdl {
   protected boolean isTrue(Boolean value) {
     return Boolean.TRUE.equals(value);
   }
+
+  /**
+   * Add an inline table comment to the create table statement.
+   */
+  public void inlineTableComment(DdlBuffer apply, String tableComment) throws IOException {
+    // do nothing by default (MySql only)
+  }
+
+  /**
+   * Add table comment as a separate statement (from the create table statement).
+   */
+  public void addTableComment(DdlBuffer apply, String tableName, String tableComment) throws IOException {
+
+    apply.append(String.format("comment on table %s is '%s'", tableName, tableComment)).endOfStatement();
+  }
+
+  /**
+   * Add column comment as a separate statement.
+   */
+  public void addColumnComment(DdlBuffer apply, String table, String column, String comment) throws IOException {
+
+    apply.append(String.format("comment on column %s.%s is '%s'", table, column, comment)).endOfStatement();
+  }
 }

src/main/java/com/avaje/ebean/dbmigration/model/MColumn.java

@@ -16,6 +16,7 @@ public class MColumn {
   private String references;
   private String foreignKeyName;
   private String foreignKeyIndex;
+  private String comment;
 
   private boolean historyExclude;
   private boolean notnull;
@@ -43,6 +44,7 @@ public class MColumn {
     this.checkConstraint = column.getCheckConstraint();
     this.checkConstraintName = column.getCheckConstraintName();
     this.defaultValue = column.getDefaultValue();
+    this.comment = column.getComment();
     this.references = column.getReferences();
     this.foreignKeyName = column.getForeignKeyName();
     this.foreignKeyIndex = column.getForeignKeyIndex();
@@ -76,6 +78,7 @@ public class MColumn {
     copy.checkConstraintName = checkConstraintName;
     copy.defaultValue = defaultValue;
     copy.references = references;
+    copy.comment = comment;
     copy.foreignKeyName = foreignKeyName;
     copy.foreignKeyIndex = foreignKeyIndex;
     copy.historyExclude = historyExclude;
@@ -198,6 +201,19 @@ public class MColumn {
     return uniqueOneToOne;
   }
 
+  /**
+   * Return the column comment.
+   */
+  public String getComment() {
+    return comment;
+  }
+
+  /**
+   * Set the column comment.
+   */
+  public void setComment(String comment) {
+    this.comment = comment;
+  }
 
   /**
    * Set the draftOnly status for this column.
@@ -237,6 +253,7 @@ public class MColumn {
     c.setForeignKeyName(foreignKeyName);
     c.setForeignKeyIndex(foreignKeyIndex);
     c.setDefaultValue(defaultValue);
+    c.setComment(comment);
     c.setUnique(unique);
     c.setUniqueOneToOne(uniqueOneToOne);
 

src/main/java/com/avaje/ebean/dbmigration/model/MTable.java

@@ -325,6 +325,10 @@ public class MTable {
     return comment;
   }
 
+  public void setComment(String comment) {
+    this.comment = comment;
+  }
+
   public String getTablespace() {
     return tablespace;
   }

src/main/java/com/avaje/ebean/dbmigration/model/build/ModelBuildBeanVisitor.java

@@ -35,6 +35,7 @@ public class ModelBuildBeanVisitor implements BeanVisitor {
     }
 
     MTable table = new MTable(descriptor.getBaseTable());
+    table.setComment(descriptor.getDbComment());
     if (descriptor.isHistorySupport()) {
       table.setWithHistory(true);
       BeanProperty whenCreated = descriptor.findWhenCreatedProperty();

src/main/java/com/avaje/ebean/dbmigration/model/build/ModelBuildPropertyVisitor.java

@@ -230,6 +230,7 @@ public class ModelBuildPropertyVisitor extends BaseTablePropertyVisitor {
     }
 
     MColumn col = new MColumn(p.getDbColumn(), ctx.getColumnDefn(p));
+    col.setComment(p.getDbComment());
     col.setDraftOnly(p.isDraftOnly());
 
     if (p.isId()) {

src/main/java/com/avaje/ebeaninternal/server/deploy/BeanDescriptor.java

@@ -155,6 +155,11 @@ public class BeanDescriptor<T> implements MetaBeanInfo, SpiBeanType<T> {
 
   private final String draftTable;
 
+  /**
+   * DB table comment.
+   */
+  private final String dbComment;
+
   /**
    * Set to true if read auditing is on for this bean type.
    */
@@ -397,6 +402,7 @@ public class BeanDescriptor<T> implements MetaBeanInfo, SpiBeanType<T> {
     this.baseTable = InternString.intern(deploy.getBaseTable());
     this.baseTableAsOf = deploy.getBaseTableAsOf();
     this.baseTableVersionsBetween = deploy.getBaseTableVersionsBetween();
+    this.dbComment = deploy.getDbComment();
     this.autoTunable = EntityType.ORM.equals(entityType) && (beanFinder == null);
 
     // helper object used to derive lists of properties
@@ -1936,6 +1942,13 @@ public class BeanDescriptor<T> implements MetaBeanInfo, SpiBeanType<T> {
     return EntityType.SQL.equals(entityType);
   }
 
+  /**
+   * Return the DB comment for the base table.
+   */
+  public String getDbComment() {
+    return dbComment;
+  }
+
   /**
    * Return the base table. Only properties mapped to the base table are by
    * default persisted.

src/main/java/com/avaje/ebeaninternal/server/deploy/BeanProperty.java

@@ -211,6 +211,11 @@ public class BeanProperty implements ElPropertyValue {
    */
   final String dbColumnDefn;
 
+  /**
+   * Database DDL column comment.
+   */
+  final String dbComment;
+
   /**
    * DB Constraint (typically check constraint on enum)
    */
@@ -298,6 +303,7 @@ public class BeanProperty implements ElPropertyValue {
     this.setter = deploy.getSetter();
 
     this.dbColumn = tableAliasIntern(descriptor, deploy.getDbColumn(), false, null);
+    this.dbComment = deploy.getDbComment();
     this.sqlFormulaJoin = InternString.intern(deploy.getSqlFormulaJoin());
     this.sqlFormulaSelect = InternString.intern(deploy.getSqlFormulaSelect());
     this.formula = sqlFormulaSelect != null;
@@ -377,6 +383,7 @@ public class BeanProperty implements ElPropertyValue {
     this.secondaryTableJoin = source.secondaryTableJoin;
     this.secondaryTableJoinPrefix = source.secondaryTableJoinPrefix;
 
+    this.dbComment = source.dbComment;
     this.dbBind = source.getDbBind();
     this.dbEncrypted = source.isDbEncrypted();
     this.dbEncryptedType = source.getDbEncryptedType();
@@ -999,6 +1006,13 @@ public class BeanProperty implements ElPropertyValue {
     return dbColumn;
   }
 
+  /**
+   * Return the comment for the associated DB column.
+   */
+  public String getDbComment() {
+    return dbComment;
+  }
+
   /**
    * Return the database jdbc data type this is mapped to.
    */

src/main/java/com/avaje/ebeaninternal/server/deploy/meta/DeployBeanDescriptor.java

@@ -165,6 +165,9 @@ public class DeployBeanDescriptor<T> {
 
   private ChangeLogFilter changeLogFilter;
 
+  private String dbComment;
+
+
   /**
    * Construct the BeanDescriptor.
    */
@@ -207,6 +210,14 @@ public class DeployBeanDescriptor<T> {
     return readAuditing;
   }
 
+  public void setDbComment(String dbComment) {
+    this.dbComment = dbComment;
+  }
+
+  public String getDbComment() {
+    return dbComment;
+  }
+
   public void setDraftable() {
     draftable = true;
   }

src/main/java/com/avaje/ebeaninternal/server/deploy/meta/DeployBeanProperty.java

@@ -193,6 +193,8 @@ public class DeployBeanProperty {
 
   private boolean softDelete;
 
+  private String dbComment;
+
   public DeployBeanProperty(DeployBeanDescriptor<?> desc, Class<?> propertyType, ScalarType<?> scalarType, ScalarTypeConverter<?, ?> typeConverter) {
     this.desc = desc;
     this.propertyType = propertyType;
@@ -898,4 +900,11 @@ public class DeployBeanProperty {
     return softDelete;
   }
 
+  public void setDbComment(String dbComment) {
+    this.dbComment = dbComment;
+  }
+
+  public String getDbComment() {
+    return dbComment;
+  }
 }

src/main/java/com/avaje/ebeaninternal/server/deploy/parse/AnnotationClass.java

@@ -9,6 +9,7 @@ import javax.persistence.UniqueConstraint;
 
 import com.avaje.ebean.annotation.CacheStrategy;
 import com.avaje.ebean.annotation.CacheTuning;
+import com.avaje.ebean.annotation.DbComment;
 import com.avaje.ebean.annotation.Draftable;
 import com.avaje.ebean.annotation.DraftableElement;
 import com.avaje.ebean.annotation.EntityConcurrencyMode;
@@ -120,6 +121,11 @@ public class AnnotationClass extends AnnotationParser {
       descriptor.setHistorySupport();
     }
 
+    DbComment comment = cls.getAnnotation(DbComment.class);
+    if (comment != null) {
+      descriptor.setDbComment(comment.value());
+    }
+
     UpdateMode updateMode = cls.getAnnotation(UpdateMode.class);
     if (updateMode != null) {
       descriptor.setUpdateChangesOnly(updateMode.updateChangesOnly());

src/main/java/com/avaje/ebeaninternal/server/deploy/parse/AnnotationFields.java

@@ -166,6 +166,10 @@ public class AnnotationFields extends AnnotationParser {
       prop.setSoftDelete();
     }
 
+    DbComment comment = get(prop, DbComment.class);
+    if (comment != null) {
+      prop.setDbComment(comment.value());
+    }
     DbJson dbJson = get(prop, DbJson.class);
     if (dbJson != null) {
       util.setDbJsonType(prop, dbJson);