SqlTemplate 是sql模板引擎，主要解决动态拼接sql字符串 。原理是比较简单，把模板内容构建成完成的xml，这样可以解析成相关的数据结构， 再结合Ognl强大表达式计算条件。设计上参考了MyBatis动态sql部分，为了减少学习成本，兼容Mybatis大部分用法。目前能支持以下标签：
- if
- choose (when, otherwise)
- trim ， where, set
- foreach
详细用法，请参考MyBatis
例1：动态查询
SqlTemplateEngin sqlTemplateEngin = new SqlTemplateEngin();
String sqlTpl = "select * from user_info <where><if test=' username != null' > and username = #{username} </if><if test=' email != null' > and email = #{email} </if></where> ";
//从字符串读取sql模板内容,还可以从单独的文件读取
SqlTemplate sqlTemplate = sqlTemplateEngin.getSqlTemplate(sqlTpl) ;
Bindings bind = new Bindings().bind("email", "[email protected]");
SqlMeta sqlMeta = sqlTemplate.process(bind) ; //可传map对象或javabean对象
//System.out.println(sqlMeta.getSql());
Assert.assertEquals("select * from user_info WHERE email = ? ", sqlMeta.getSql());
List<Object> parameter = sqlMeta.getParameter(); //取出参数
Assert.assertEquals(1, parameter.size());
bind.bind("username", "wenzuojing") ;
sqlMeta = sqlTemplate.process(bind) ;
Assert.assertEquals("select * from user_info WHERE username = ? and email = ? ", sqlMeta.getSql());
List<Object> parameter2 = sqlMeta.getParameter();//取出参数
Assert.assertEquals( 2 ,parameter2.size() );
例2：动态更新 SqlTemplateEngin sqlTemplateEngin = new SqlTemplateEngin();
Map<String ,Object > userInfo = new HashMap<String,Object>() ;
userInfo.put("id", "123456") ;
userInfo.put("email", "[email protected]") ;
String sqlTpl =" update userinfo <set> <if test ='email != null '> email = #{email} </if>, <if test='age'> age = #{age} </if> </set> where id = #{id}" ;
SqlTemplate sqlTemplate = sqlTemplateEngin.getSqlTemplate(sqlTpl) ;
SqlMeta sqlMeta = sqlTemplate.process(userInfo) ;
Assert.assertEquals(" update userinfo SET email = ? where id = ? ", sqlMeta.getSql());
List<Object> parameter = sqlMeta.getParameter(); //取出参数
Assert.assertEquals(2, parameter.size());
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