Added Getting Started doc.

Author: elw00d

README.md

@@ -7,4 +7,122 @@ MyBatis FreeMarker Support
 
 MyBatis FreeMarker Scripting Support.
 
-See tests to view examples.
+Getting started
+===============
+
+## Introduction
+
+mybatis-freemarker is a plugin that helps creating big dynamic SQL queries. You can use it selectively, to only queries that need if statmenets or foreach-loops, for example. But it is possible to use this syntax by default too.
+
+If you are not familiar with FreeMarker syntax, you can view [Template Language Reference](http://freemarker.org/docs/ref.html)
+
+## Install from sources
+
+- Checkout the source code
+- Run `mvn install` to build and to automatically install it to your local maven repo
+- Add maven dependency to your project
+
+```xml
+<dependency>
+  <groupId>org.mybatis.scripting</groupId>
+  <artifactId>mybatis-freemarker</artifactId>
+  <version>1.0-SNAPSHOT</version>
+</dependency>
+```
+
+## Configuring
+
+### Common
+
+- (Optional) Create `mybatis-freemarker.properties` file in your classpath:
+
+```
+basePackage=sql
+```
+
+This will define base package to search FreeMarker templates. By default it is empty string, so you will need to provide full path to template every time.
+
+### XML-driven mappers
+
+If your are using annotations-driven mappers, you don't need to do anything more. If you are using XML-driven mappers too, you may need to do next steps:
+
+- Register the language driver alias in your mybatis configuration file:
+
+```xml
+<configuration>
+  ...
+  <typeAliases>
+    <typeAlias alias="freemarker" type="org.mybatis.scripting.freemarker.FreeMarkerLanguageDriver"/>
+  </typeAliases>
+  ...
+</configuration>
+```
+
+- (Optional) Set the freemarker as your default scripting language:
+
+```xml
+<configuration>
+  ...
+  <settings>
+      <setting name="defaultScriptingLanguage" value="freemarker"/>
+  </settings>
+  ...
+</configuration>
+```
+
+## Usage in annotations-driven mappers
+
+Just write your queries using FreeMarker syntax:
+
+```java
+@Lang(FreeMarkerLanguageDriver.class)
+@Select("select * from names where id in (${ids?join(',')})")
+List<Name> findNamesByIds(@Param("ids") List<Integer> ids);
+```
+
+If any whitespace found inside `@Select` text, it is interpreted as inline script, not template name. It is convenient to avoid creating templates when script is really small. If you have a large SQL script, you can place it in distinct template and write next code:
+
+```java
+@Lang(FreeMarkerLanguageDriver.class)
+@Select("findName.ftl")
+Name findName(@Param("n") String name);
+```
+
+Template will be searched in classpath using `basePackage` property that has already been described above.
+
+`findName.ftl` content can be:
+
+```
+SELECT *
+FROM names
+where firstName = <@p name="n"/>
+```
+
+`<@p name="n"/>` is a custom directive to generate `#{n}` markup. This markup further will be passed into MyBatis engine, and it will replace this to `?`-parameter. You can't write `#{paramName}` directly, because FreeMarker supports this syntax natively (alghough it is deprecated). So, to get `?`-parameters to prepared statements works, you need to use `${r"#{paramName}"}` verbose syntax, or this directive. By the way, in XML files `${r"#{paramName}"}` is more preferrable because you don't need wrap it using `CDATA` statements. In annotations and in external templates `<@p/>` directive is more neat.
+
+## Usage in XML-driven mappers
+
+As in annotations, you can write inline scripts or template names.
+
+```xml
+<!-- This is handled by FreeMarker too, because it is included into select nodes AS IS -->
+<sql id="cols">id, ${r"firstName"}, lastName</sql>
+
+<select id="findName" resultType="org.mybatis.scripting.freemarker.Name" lang="freemarker">
+    findName.ftl
+</select>
+
+<select id="findNamesByIds" resultType="org.mybatis.scripting.freemarker.Name" lang="freemarker">
+    select <include refid="cols"/> from names where id in (${ids?join(',')})
+</select>
+
+<!-- It is not very convenient - to use CDATA blocks. Better is to create external template
+    or use more verbose syntax: ${r"#{id}"}. -->
+<select id="find" resultType="org.mybatis.scripting.freemarker.Name" lang="freemarker">
+    select * from names where id = <![CDATA[ <@p name='id'/> ]]> and id = ${id}
+</select>
+```
+
+## Examples
+
+You can view full-featured example of configuring and of both XML-mapper and annotations-driven mapper usage in [test suite](https://github.com/elw00d/mybatis-freemarker/tree/master/src/test)