iBATIS is a persistence framework which automates the mapping between SQL databases and 1 Usage; 2 Availability; 3 History; 4 See also; 5 References; 6 Bibliography It was a complete redesign while keeping the same features. Reference Documentation; Introduction; Getting Started · Configuration MyBatis is a first class persistence framework with support for custom SQL, MyBatis can use simple XML or Annotations for configuration and map. Reference Documentation; Introduction · Getting Started One of the most powerful features of MyBatis has always been its Dynamic SQL capabilities. While working with Dynamic SQL will never be a party, MyBatis.
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If you have any experience with JDBC or any similar framework, you understand how painful it is to conditionally concatenate strings of SQL together, making sure not to forget spaces or to omit a comma at the referende of a list of columns. Dynamic SQL can be downright painful to deal with. In previous versions of MyBatis, there were a lot of elements to know and understand.
MyBatis 3 greatly improves upon this, and now there are less than half of those elements to work with. The most common clmplete to do in dynamic SQL is conditionally include a part of a where clause.
Apache iBATIS – Wikipedia
This statement would provide an optional text search type of functionality. Compldte you passed in no title, then all active Blogs would be returned. But if you do pass in a title, it will look for a title like that for the keen eyed, yes in this case your parameter value would need to include any masking or wildcard characters.
What if we wanted to optionally search by title and author? Then simply add another condition. Similar to a switch statement in Java, MyBatis offers a choose element. The previous examples have been conveniently dancing around a notorious dynamic SQL challenge. What happens if none of the conditions are met? You would end up with SQL that looked like this:. What if only the compplete condition was met? This would also fail. With one simple change, complette works fine:.
Part 1 Introduction
The where element knows to only insert “WHERE” if there is any content returned by the containing tags. If the where element does not behave exactly as you like, you can customize it by defining rreference own trim element. For example, the trim equivalent to the where element is:.
The prefixOverrides attribute takes a pipe delimited list of text to override, where whitespace is relevant. The result is the removal of anything specified in the prefixOverrides attribute, and the insertion of anything in the prefix attribute.
There is a similar solution for dynamic update statements called set. The set element can be used to dynamically include columns to update, and leave out others. Here, the set element will dynamically prepend the SET keyword, and also eliminate any extraneous commas that might trail kbatis value assignments after the conditions are applied.
Another common necessity for dynamic SQL is referebce need to iterate over a collection, often to build an IN condition. The foreach element is very powerful, and allows you to specify a collection, declare item and index variables that can be used inside the body of the element. It also allows you to specify opening and closing strings, and add a separator to place in between iterations.
When using an Iterable or Array, index will be the number of current iteration and value item will be the element retrieved in this iteration. When using a Map or Collection of Map. Entry objectsindex will be the key object and item will be the value object. The bind element lets you create a variable out of an OGNL expression and bind it to the context.
Have a look at the following example:.
Starting from version 3. Once you have your custom language driver you refeerence set it to be the default by configuring it in the mybatis-config. Instead of changing the default, you can specify the language for an specific statement by adding the lang attribute as follows:. Have a look at the MyBatis-Velocity project for the details. All the xml tags you have seen in the previous sections are provided by the default MyBatis language that is provided by the driver org.
XmlLanguageDriver which is aliased as xml. Have a look at the following example: You can plug a language by implementing the following interface: