Merge pull request #288 from domaframework/example

Put example code in README.md

Author: nakamura-to

README.md

@@ -3,23 +3,70 @@ Doma [![Build Status](https://travis-ci.org/domaframework/doma.svg?branch=master
 
 [![Join the chat at https://gitter.im/domaframework/doma](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/domaframework/doma?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-Doma is a Database access framework for Java. 
+Doma is a database access framework for Java. 
+Doma uses [Pluggable Annotation Processing API][apt] to generate source code and validate sql mappings **at compile time**.
 
-Doma uses [Pluggable Annotation Processing API][apt] to generate source code and validate sql mappings at **compile time**.
+Example
+---------------------
+
+Define an entity class:
+```java
+@Entity
+public class Employee {
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE)
+    @SequenceGenerator(sequence = "EMPLOYEE_SEQ")
+    public Integer id;
+    public String name;
+    public Integer age;
+    @Version
+    public Integer version;
+}
+```
+
+Define a DAO interface:
+```java
+@Dao(config = AppConfig.class)
+public interface EmployeeDao {
+    @Select
+    List<Employee> selectAll();
+    @Update
+    int update(Employee employee);
+}
+```
 
-![doma](https://github.com/domaframework/doma/blob/master/docs/images/doma.png)
+Execute queries:
+```java
+public class App {
+    public static void main(String[] args) {
+        TransactionManager tm = AppConfig.singleton().getTransactionManager();
+        tm.required(() -> {
+            EmployeeDao dao = new EmployeeDaoImpl();
+            Employee employee = dao.selectById(1);
+            employee.age++;
+            dao.update(employee);
+        });
+    }
+}
+```
+
+
+Documentation
+---------------------
+
+https://doma.readthedocs.io/
 
 Major versions
 ---------------------
 
+### Status and Repository
+
 | Version                                | Status            | Repository                             | Branch |
 | -------------------------------------- | ----------------- | -------------------------------------- | ------ |
 | [Doma 1](http://doma.seasar.org/)      | stable            | https://github.com/seasarorg/doma/     | master |
 | [Doma 2](http://doma.readthedocs.org/) | stable            | https://github.com/domaframework/doma/ | master |
 
-
-Compatibility matrix
--------------------------
+### Compatibility matrix
 
 |         | Doma 1 | Doma 2 |
 | ------- | ------ | ------ |