4.参数绑定

代码分支：04-parameter-binding-with-param-annotation

本章节包含如下三种方式的参数解析

1. @Param注解
2. 单个参数
3. 简单POJO对象

TypeHandler接口用于不同数据类型参数的处理，TypeHandlerRegistry负责注册TypeHandler，其中包含了像String，Integer等常用类型的处理器；LanguageDriver可以创建参数处理器ParameterHandler和SQL资源SqlSource，其中ParameterHandler可以设置PreparedStatement的参数，SqlSource可以获取sql语句和参数集合信息；ParamNameResolver用于参数名称解析；GenericTokenParser和TokenHandler共同实现了解析xml中sql为可执行的预处理sql，同时，提取sql参数信息为ParameterMapping。

单元测试：

public class SqlSessionTest {

    /**
     * Param注解绑定参数
     */
    @Test
    public void insertWithParam() {
        Configuration configuration = new Configuration();
        configuration.setDataSource(DataSourceBuilderTest.build());
        configuration.addMapper(UserMapper.class);
        SqlSession sqlSession = new DefaultSqlSession(configuration);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.insertWithParam("Alice", 23);
    }

    /**
     * 支持传null
     */
    @Test
    public void insertWithParamNullable() {
        Configuration configuration = new Configuration();
        configuration.setDataSource(DataSourceBuilderTest.build());
        configuration.addMapper(UserMapper.class);
        SqlSession sqlSession = new DefaultSqlSession(configuration);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.insertWithParam("Jack", null);
    }

    /**
     * 无Param注解的单个参数
     * 单个参数没有设置Param注解时，无需参数名称和xml中变量名相同
     */
    @Test
    public void insertWithoutParam() {
        Configuration configuration = new Configuration();
        configuration.setDataSource(DataSourceBuilderTest.build());
        configuration.addMapper(UserMapper.class);
        SqlSession sqlSession = new DefaultSqlSession(configuration);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.insertWithoutParam("Tom");
    }

    /**
     * 简单对象
     */
    @Test
    public void insertWithPOJO() {
        Configuration configuration = new Configuration();
        configuration.setDataSource(DataSourceBuilderTest.build());
        configuration.addMapper(UserMapper.class);
        SqlSession sqlSession = new DefaultSqlSession(configuration);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        UserDO user = new UserDO();
        user.setName("Sam");
        user.setAge(20);
        userMapper.insertWithPOJO(user);
    }
}