写在前面

以前有点懒，一直没有分享技术新的的习惯，这次居然有心情写点东西分享出来。
作为一个从很老很老的jdk就开始码java代码的码农，对Mybatis却一直都是一无所知，一直固守在Hibernate持久层框架上。虽然这个红的发紫的MyBatis 是一款优秀的持久层框架，而我居然都没有了解过，也没有用过。想想也觉得汗颜呀。
言归正传，现在切入正题。
还有需要先申明一下：本文档为本人原创，欢迎引用，本着方便字节，也方便大家的原则，独乐乐，众乐乐，不若与众的精神，只有能给大家工作带来用处，本老农就心满意足了。

背景，为什么要学习

因项目需要，决定采用springboot+Mybatis。于是，我也加入了这个码农圈无人不知，无人不晓的Mybatis开发大队伍里。据说：这个可是各个大厂的御用持久层技术框架，一时用一时爽，一直用就一直爽；还听说，Mybatis能够让你随心所欲写SQL。
以前使用hibernate，对hibernate的一些使用习惯还是念念不忘，总想Mybatis能有该多好。真的是如假包换，百分百的hibernate的添狗一只。
因项目，在这个项目开始前开始学习Mybatis，翻资料，网上找例子，就差去整一本《二十一天精通Mybatis》来了。不过，从开始学习，接触Mybatis开始算起，已经2周左右了，马上就差不多要到21天了，感觉离精通还有十万八千里路远。
就这样子，还班门弄斧，各位看官，莫笑。如不听劝，牙齿掉了，还请自负其责，自费补牙。

Mybatis的典型规范

典型的规范：

1. 写个实体EntityBean类，描述数据库表或查询结构之间的映射关系。

@Entity
@Table(name = "User")
public class User{@Idprivate int id;private String name;……} 

2. 写个Mapper接口，定义访问数据库表的方法。Mybatis采用JDK本身的接口动态代理实现。

public interface UserMapper {  //根据用户id查询用户信息  public User findUserById(int id) throws Exception;  //查询用户列表  public List<User> findUserByUsername(String username) throws Exception;  //添加用户信息  public void insertUser(User user)throws Exception;   ……}

3. 写一个.XML文件，配置Mapper接口方法所需要的SQL语句，为了实现一定的动态能力，还定义了一套XML标签来标记条件、循环等。

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE mapper  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"  
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">  
<mapper namespace="com.xxx.UserMapper">  
<!-- 注意这里的 namespace必须对应着map接口的全类名-->  <select id="findUserById" parameterType="int" resultType="user">  select * from user where id = #{id}  </select>  <select id="findUserByUsername" parameterType="java.lang.String"  resultType="user">  select * from user where username like '%${value}%'  </select>  <insert id="insertUser" parameterType="user">  <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">  select LAST_INSERT_ID()  </selectKey>  insert into user(username,birthday,sex,address)  values(#{username},#{birthday},#{sex},#{address})  </insert>  
……
</mapper>  

为了写好这三个文件，还有大拿提供了专门的脚手架插件来完成这个事情，不过，为了与前端页面配合，编辑调试XML的工作还是有不少的。

懒人的想法

1.以前用Hibernate时，只定义了一个基础接口，把常用的增删改查放在基类接口中，在扩展接口中定义少量的个性化方法，利用注解的方式和JDK和CGLIB的动态代理机制，实现接口功能。Mybatis能不能也像Hibernate一样，直接定义个通用接口就好了，再也不用配置XML或注解SQL。减少码代码的工作量和测试工作量。
2.Mybatis分页方式，大多采用应用层分页方式实现，应用层分页，数据会从数据库服务器向应用服务器传输。当数据集特别大，比如十万级百万级甚至千万级时，数据从数据库服务器向应用服务器传输，给网络带来了非常大的压力。那能不能实现任意字段方式的查询，以及真正的数据库端的分页呢？
说干就干，本着辛苦我一人，造福兄弟伙的国际奉献主义精神，我不当垫脚石谁来当垫脚石的牺牲精神。我这个21天都不到的Mybatis的婴儿码农脱了衣服，再撸起袖子加油干。

突破口在哪儿

翻了一堆的资料，找下手的突破口。功夫不负我心，找到了两个下手地。首先，我来看看Mybatis的执行过程。

1.Mybatis提供有方法拦截器的切入口。Mybatis支持对Executor、StatementHandler、PameterHandler和ResultSetHandler 接口的方法进行拦截，也就是说会对这4类对象的方法进行代理拦截。

在mybatis中可被拦截的类型有四种(按照拦截顺序)：

1. Executor：拦截执行器的方法。
2. ParameterHandler：拦截参数的处理。
3. ResultHandler：拦截结果集的处理。
4. StatementHandler：拦截Sql语法构建的处理。

2.针对动态拼接SQL, Mybatis3中增加了使用注解来配置Mapper的新特性，我们主要用到@SelectProvider、@UpdateProvider、@InsertProvider和@DeleteProvider几个注解来实现。
有了这些注解，就可以让我们在运行时将SQL构造出来。实现动态SQL生成，处理数据。换句话说，就是可以根据传进来的实体类型及字段值，就可以组装出你想要的SQL。这样做是不是很爽。
有了这两个切入点，我们就可以在完全不破坏Mybatis架构的前提下，把我们的私心暗恋想法悄无声息地注入进去。光想一下都让我有点鸡冻不已。激动让我语无伦次，必须马上动手实现它。不能光临渊羡鱼，还得退而结网
让我们来看看下面这幅图，我们要下手的地方在哪儿。

进入正题

为了少写点代码，把经常用到的通用方法放在基类接口中，不使用XML，子类接口直接继承就好了。
废话就不BB了，直接上代码:
由于文档篇幅，下面提供主要类的部分代码片段。进行示例。

A. 基类接口

定义基类接口，基类接口实现　
1.数据处理操作，包括insert,update,delete,save(自动判断使用insert或update)方法，
2.数据库查询操作，包括分页查询。查询条件参数支持map、dto对象，EntityBean对象
Mapper接口泛型GenericMapper，提供子类对具体实体类的支持。

public interface GenericMapper<T> {@SelectProvider(type = GenericSelectProvider.class, method = "getById")T getById(@Param("entityClass") Class<T> entityClass, @Param("entityId") Object params);@SelectProvider(type = GenericSelectProvider.class, method = "query")List<T> query(@Param("entityClass") Class<T> entityClass,@Param("params") Map params,String orderBy);@SelectProvider(type = GenericSelectProvider.class, method = "pagedQuery")Paginate<T> pagedQuery(@Param("entityClass") Class<T> entityClass,@Param("paginate") Paginate<T> paginate,@Param("params") Map params,String orderBy);@SelectProvider(type = GenericSelectProvider.class, method = "count")int count(@Param("entityClass") Class<T> entityClass,@Param("params") Map params);@SelectProvider(type = GenericSelectProvider.class, method = "queryByDto")List<T> queryByDto(@Param("entityClass") Class<T> entityClass,@Param("params") Object params,String orderBy);@SelectProvider(type = GenericSelectProvider.class, method = "queryByFilterRules")List<T> queryByFilterRules(@Param("entityClass") Class<T> entityClass,@Param("filterRules") List<DataFilterRule> filterRules,String orderBy);@InsertProvider(type = GenericSaveProvider.class, method = "insert")Integer insert(@Param("entityBean") T entityBean);@UpdateProvider(type = GenericSaveProvider.class, method = "update")Integer update(@Param("entityBean") T entityBean);@DeleteProvider(type = GenericSaveProvider.class, method = "delete")Integer remove(@Param("entityBean") T entityBean);@UpdateProvider(type = GenericSaveProvider.class, method = "save")Integer save(@Param("entityBean") T entityBean);}

B. 提供Mybatis使用的Providor

Providor提供动态sql切入点。GenericSelectProvidor提供实体类或查询对象的动态数据查询的切入点，GenericSaveProvidor提供对通用实体类的动态增删改操作。

1. GenericSelectProvidor代码

public class GenericSelectProvider {private final Logger logger = LoggerFactory.getLogger(this.getClass());	protected static final String SQL_END_DELIMITER = ";";  @SelectProvider(type = GenericSelectProvider.class, method = "getById")public <T> String getById(@Param("entityClass") Class<T> entityClass, @Param("entityId") Object params){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}String sql=dmi.getGetByIdSQL();return sql;}public <T> String query(@Param("entityClass") Class<T> entityClass, @Param("params") Map<String,Object> params,String orderBy){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}String sql=dmi.getSelectSQL();		Map<String,ColumnInfo> columns=dmi.getColumns();String whereClause = whereClause(columns,params);		String _orderBy = orderByClause(dmi.getColumns(),orderBy);if (whereClause!=null && whereClause.length()>0){sql=insertWhereClause(sql,whereClause);}if (_orderBy!=null && _orderBy.length()>0){sql=sql+"\r\n order by " + _orderBy;}logger.debug("mybatis get query sql:{}", sql);return sql;}private String insertWhereClause(String sql,String whereClause){int wherePos=SqlUtil.indexOfKeywordInSql(sql, "where");if (wherePos<1){sql=sql+"\r\n where " + whereClause;				}else{int groupPos = SqlUtil.indexOfKeywordInSql(sql, "group", wherePos + 5);int orderPos = SqlUtil.indexOfKeywordInSql(sql, "order", wherePos + 5);int insertPos = wherePos < groupPos ? groupPos : wherePos;insertPos = insertPos < orderPos ? orderPos : insertPos;if (insertPos != wherePos) {sql = sql.substring(0, insertPos) + "\r\n and " + whereClause + "\r\n" + sql.substring(insertPos);} else {sql = sql + "\r\n and " + whereClause;}}return sql;}public <T> String pagedQuery(@Param("entityClass") Class<T> entityClass,@Param("paginate") Paginate<T> paginate,@Param("params") Map params,String orderBy){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}Map<String,ColumnInfo> columns=dmi.getColumns();String whereClause = whereClause(columns,params);		String _orderBy = orderByClause(dmi.getColumns(),orderBy);String slctSql=dmi.getSelectSQL();		if (whereClause!=null && whereClause.length()>0){slctSql=insertWhereClause(slctSql,whereClause);}if (_orderBy!=null && _orderBy.length()>0){slctSql=slctSql+"\r\n order by " + _orderBy;}logger.debug("GenericSelectProvider.pagedquery() sql:{}", slctSql);//System.out.println("slctsql:"+slctSql);return slctSql;		}public <T> String count(@Param("entityClass") Class<T> entityClass, @Param("params") Map<String,Object> params){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}String sql=dmi.getCountSQL();		Map<String,ColumnInfo> columns=dmi.getColumns();String whereClause = whereClause(columns,params);		if (whereClause!=null && whereClause.length()>0){sql=sql+"\r\n where " + whereClause;}logger.debug("GenericSelectProvider.count() sql:{}", sql);//System.out.println("count sql:"+sql);return sql;}private String whereClause(Map<String,ColumnInfo> columns, Map<String,Object> params){StringBuffer whereClause=new StringBuffer();params.forEach((paraName,paraValue)->{getCondition(paraName,paraValue,columns,whereClause);});return whereClause.toString();}public <T> String queryByDto(@Param("entityClass") Class<T> entityClass,@Param("params") Object params,String orderBy){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}String sql=dmi.getSelectSQL();		Map<String,ColumnInfo> columns=dmi.getColumns();String whereClause = whereClause(columns,params);String _orderBy = orderByClause(dmi.getColumns(),orderBy);if (whereClause!=null && whereClause.length()>0){sql=insertWhereClause(sql,whereClause);}if (_orderBy!=null && _orderBy.length()>0){sql=sql+"\r\n order by " + _orderBy;}logger.debug("GenericSelectProvider.queryByDto() sql:{}", sql);return sql;		}private String whereClause(Map<String,ColumnInfo> columns, Object params){StringBuffer whereClause=new StringBuffer();Field[] fields=params.getClass().getDeclaredFields();String paraName;Object paraValue;for(Field field:fields){paraName=field.getName();try {paraValue=BeanUtils.forceGetProperty(params, paraName);if (paraValue==null)continue;} catch (NoSuchFieldException e) {continue;}getCondition(paraName,paraValue,columns,whereClause);}return whereClause.toString();}public <T> String queryByFilterRules(@Param("entityClass") Class<T> entityClass, @Param("filterRules") List<DataFilterRule> filterRules,String orderBy){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(entityClass);if (dmi==null){throw new RuntimeException("不是数据库映射对象");}String sql=dmi.getSelectSQL();		Map<String,ColumnInfo> columns=dmi.getColumns();String whereClause = whereClause(columns,filterRules);String _orderBy = orderByClause(dmi.getColumns(),orderBy);if (whereClause!=null && whereClause.length()>0){sql=insertWhereClause(sql,whereClause);}if (_orderBy!=null && _orderBy.length()>0){sql=sql+"\r\n order by " + _orderBy;}logger.debug("GenericSelectProvider.queryByFilterRules() sql:{}", sql);return sql;}private String whereClause(Map<String,ColumnInfo> columns, List<DataFilterRule> filterRules){StringBuffer whereClause=new StringBuffer();String paraName;Object paraValue;for(DataFilterRule rule:filterRules){paraName=rule.getField();paraValue=rule.getValue();if (paraValue==null)continue;getCondition(paraName,paraValue,columns,whereClause);}return whereClause.toString();}private void getCondition(String paraName,Object paraValue,Map<String,ColumnInfo> columns,StringBuffer whereClause){//基本条件：属性等于属性值String field,queryMode;ColumnInfo column=columns.get(paraName);Class<?> type;if (column != null){if (!column.isFilterable()){return;}if (whereClause.length()>0)whereClause.append(" and ");type=column.getJavaType();whereClause.append(column.getFilterName()).append(" = #{params.").append(paraName).append("}");return ;}//复杂条件：参数为 属性名_条件类型//条件类型为：包含，多值，大于，小于等。int pos;pos=paraName.lastIndexOf("_");if (pos<0){//单值查询field=paraName;queryMode="";}else{field=paraName.substring(0,pos);queryMode=paraName.substring(pos+1);			}column=columns.get(field);if (column==null || !column.isFilterable())return;type=column.getJavaType();if (queryMode.indexOf("multiple")<0){if (paraValue==null) return;if ((paraValue instanceof String) && ((String )paraValue).trim().length()==0 )return;getCondition(column.getFilterName(),paraName,queryMode,type,paraValue,whereClause);}else{if (paraValue instanceof Collection) {String value="";for(Object str:((Collection<?>)paraValue)){value+=str+",";}getCondition(column.getFilterName(),paraName,queryMode,type,value.substring(0,value.length()-1),whereClause);	}}}private void getCondition(String field,String paraName,String queryMode,Class<?> type,Object value,StringBuffer whereClause){if (queryMode.length()==0){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" = #{params.").append(paraName).append("}");}else{if ("begin".equalsIgnoreCase(queryMode)){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" >= #{params.").append(paraName).append("}");}if ("end".equalsIgnoreCase(queryMode)){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" <= #{params.").append(paraName).append("}");}if ("like".equalsIgnoreCase(queryMode)){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" like concat(#{params.").append(paraName).append("},'%')");}if ("likeAll".equalsIgnoreCase(queryMode)){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" like concat('%',#{params.").append(paraName).append("},'%')");}//多值in查询if ("multiple[]".equalsIgnoreCase(queryMode)){createInClause(field,type,value,whereClause);}}}protected String castType(Class<?> type,Object value){if (type==null){return value.toString();}if (type == String.class){return "'"+value+"'";}if (type == Boolean.class || type == boolean.class){return 	"'"+value+"'";}if (type == java.sql.Date.class){return "'"+value+"'";}if (type == java.util.Date.class){return "'"+value+"'";}if (type == Timestamp.class){return "'"+value+"'";}if (type == Integer.class || type == int.class){return value.toString();}if (type == Long.class || type == long.class){return value.toString();}if (type == Float.class || type == float.class){return value.toString();}if (type == Double.class || type == double.class){return value.toString();}return value.toString();}//构造多值IN查询protected void createInClause(String field,Class<?> type,Object value,StringBuffer whereClause){String[] strs=value.toString().split("\r\n|\r|\n| |,");StringBuffer sb=new StringBuffer();for (String str:strs){str=str.trim();if (str.length()==0)continue;str=str.replace("'", "''");//转义单引号，预防SQL注入sb.append(castType(type,str)+",");}if (sb.length()>1){if (whereClause.length()>0)whereClause.append(" and ") ;whereClause.append(field).append(" in (").append(sb.substring(0,sb.length()-1)).append(")");}}public String orderByClause( Map<String, ColumnInfo> columns,String orderBy){if (orderBy==null)return "";StringBuffer orderByClause=new StringBuffer();String[] orderProps=orderBy.trim().split(",");for(String op : orderProps){if (op==null)continue;orderByClause(columns,op.trim(),orderByClause);}return orderByClause.toString();}private void orderByClause(Map<String, ColumnInfo> columns,String orderBy,StringBuffer orderByClause){int pos;String propName,orderType;pos=orderBy.indexOf(" ");if (pos>1){propName=orderBy.substring(0,pos);orderType=orderBy.substring(pos+1).toLowerCase();}else{propName=orderBy;orderType="asc";}ColumnInfo columnInfo=columns.get(propName);if (columnInfo!=null){if (orderByClause.length()>0)orderByClause.append(",");orderByClause.append(columnInfo.getColumnName()).append(" ").append(orderType);}}
}

2. GenericSaveProvidor代码

public class GenericSaveProvider {public static String SAVE_ENTITY_BEAN="save";public static String SAVE_OR_UPDATE_ENTITY_BEAN="saveOrUpdate";public <T>  String update(@Param("entityBean") T entityBean){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(BeanUtils.getEntityClass(entityBean));String sql=dmi.getUpdateSQL();return sql;}public <T> String insert(@Param("entityBean") T entityBean){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(BeanUtils.getEntityClass(entityBean));		return dmi.getInsertSQL();}public <T> String delete(@Param("entityBean") T entityBean){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(BeanUtils.getEntityClass(entityBean));		String sql=dmi.getDeleteSQL();return sql;}public <T> String save(@Param("entityBean") T entityBean){EntityBeanInfo dmi=EntityBeanInfo.getDtoMaperInfo(BeanUtils.getEntityClass(entityBean));		String sql=dmi.getSaveSQL();return sql;}
}

C. 实体EntityBean描述类EntityBeanInfo

EntityBeanInfo用以描述bean信息，这个类既可以描述有@Entity和@Table注解的实体对象，也可以描述有自定义注解@BeanSQLMap注解的查询结果对象。他缓存了用于查询和修改实体对象的基本的sql语句。
用于描述EntityBean字段与数据库映射的ColumnInfo类。ColumnInfo描述了字段的属性名，读取数据时数据库字段名，查询数据库时的字段名，是否可以用于查询等，供生产动态SQL时使用。

1. EntityBeanInfo类

public class EntityBeanInfo implements Iterable<Map.Entry<Class<?>, EntityBeanInfo>>{public static Map<Class<?>, EntityBeanInfo> entityBeanInfos=new HashMap<>();private Class<?> entityClass;private Method[] methods;private Field[] fields;private BeanMappingType dataObjectType=BeanMappingType.Table;private String tableName;private String getByIdSQL;private String selectSQL;private String countSQL;private String existSQL;private String insertSQL;private String updateSQL;private String deleteSQL;private String saveSQL;private boolean hasWhereClause = false;private Map<String,ColumnInfo> columns=new HashMap<>();private List<ColumnInfo> IdColumns=new ArrayList<>();public static EntityBeanInfo getDtoMaperInfo(Class<?> entityClass){EntityBeanInfo beanInfo=entityBeanInfos.get(entityClass);if (beanInfo==null)beanInfo=createDtoMaperInfo(entityClass);return beanInfo;}public static EntityBeanInfo createDtoMaperInfo(Class<?> entityClass){EntityBeanInfo dmi=new EntityBeanInfo(entityClass);entityBeanInfos.put(entityClass, dmi);return dmi;}private EntityBeanInfo(Class<?> entityClass){this.entityClass=entityClass;getFields();	getMethods();getTableInfo();createColumns();generateIdList();createCountSQL();createSelectSQL();createInsertSQL();createUpdateSQL();createDeleteSQL();createGetByIdSQL();createExistSQL();createSaveSQL();}private void getFields(){Field[] newFieldArr=new Field[0];Field[] FieldArr,oldFieldArr;for (Class<?> superClass = entityClass; superClass != Object.class; superClass = superClass.getSuperclass()) {FieldArr=superClass.getDeclaredFields();oldFieldArr=newFieldArr;newFieldArr=new Field[oldFieldArr.length+FieldArr.length];System.arraycopy(oldFieldArr, 0, newFieldArr, 0, oldFieldArr.length);System.arraycopy(FieldArr, 0, newFieldArr, oldFieldArr.length, FieldArr.length);}fields=newFieldArr;}private void getMethods(){methods=entityClass.getMethods();Method[] newMethodArr=new Method[0];Method[] methodArr,oldMethodArr;for (Class<?> superClass = entityClass; superClass != Object.class; superClass = superClass.getSuperclass()) {methodArr=superClass.getDeclaredMethods();oldMethodArr=newMethodArr;newMethodArr=new Method[oldMethodArr.length+methodArr.length];System.arraycopy(oldMethodArr, 0, newMethodArr, 0, oldMethodArr.length);System.arraycopy(methodArr, 0, newMethodArr, oldMethodArr.length, methodArr.length);}methods=newMethodArr;}private void getTableInfo(){//对象映射到SQLBeanSQLMap sqlmap=entityClass.getAnnotation(BeanSQLMap.class);if (sqlmap != null ){String mappingSQL=sqlmap.mappingSQL();if (mappingSQL!=null && mappingSQL.trim().length()>0){selectSQL=mappingSQL;dataObjectType=BeanMappingType.Select;hasWhereClause=sqlmap.hasWhereClause();}countSQL=sqlmap.countSQL();return;}//对象映射到数据库表Table table=entityClass.getAnnotation(Table.class);if (table!=null){tableName=table.name();dataObjectType=BeanMappingType.Table;}}public List<ColumnInfo> getIdColumns() {return IdColumns;}private void generateIdList(){columns.forEach((field,column)->{if (column.getIsId())IdColumns.add(column);});}private void createColumns(){Column column;Id id;String fieldName;ColumnInfo columnInfo;ConditionColumn filter;//处理属性上有Column注解的属性for (Field field:fields){if (field.getAnnotation(Transient.class) != null)continue;fieldName=field.getName();column=field.getAnnotation(Column.class);if (column != null){fieldName=field.getName();columnInfo=new ColumnInfo(fieldName, column.table(), column.name(),  field.getType(),java.sql.Types.NULL);filter=field.getAnnotation(ConditionColumn.class);if (filter!=null){columnInfo.setFilterable(filter.filterable());if (filter.filterable() && filter.filterName()!=null && filter.filterName().length()>0){columnInfo.setFilterName(filter.filterName());}}}else{columnInfo=getFieldColumn(fieldName, field);				}if (columnInfo != null ){id=field.getAnnotation(Id.class);columnInfo.setIsId(id != null);columns.put(fieldName, columnInfo);}}//方法上注解，没有标准对应的属性。for(Method method:methods){columnInfo=getColumnFromMethod(method);if (columnInfo!=null ){id=method.getAnnotation(Id.class);boolean isId=(id != null);columnInfo.setIsId(isId);if (!columns.containsKey(columnInfo.getFieldName())){columns.put(columnInfo.getFieldName(),columnInfo);}//根据方法或属性上标志位Id,设置位主键字段columnInfo=columns.get(columnInfo.getFieldName());isId=isId||columnInfo.getIsId();columnInfo.setIsId(isId);				}}}//处理属性对应的方法上有Column注解的方法private ColumnInfo getFieldColumn(String fieldName,Field field){Column column;String methodName;String fieldGetName;ColumnInfo columnInfo;for(Method method:methods){fieldGetName=methodName=method.getName();if (methodName.startsWith("get")){fieldGetName=methodName.substring(3);}else if (methodName.startsWith("is")){fieldGetName=methodName.substring(2);}if (fieldGetName.length()==0){System.out.println("methodName:"+methodName);continue;}fieldGetName=fieldGetName.substring(0,1).toLowerCase()+fieldGetName.substring(1);if (!fieldGetName.equals(fieldName) ){continue;}if (method.getAnnotation(Transient.class) != null)continue;column=method.getAnnotation(Column.class);if (column != null){columnInfo=new ColumnInfo(fieldName, column.table(), column.name(),  field.getType(),java.sql.Types.NULL);}else{columnInfo=new ColumnInfo(fieldName, "", fieldName,  field.getType(),java.sql.Types.NULL);				}ConditionColumn filter=field.getAnnotation(ConditionColumn.class);if (filter!=null) {columnInfo.setFilterable(filter.filterable());if (filter.filterable() && filter.filterName()!=null && filter.filterName().length()>0){columnInfo.setFilterName(filter.filterName());}}Id id=field.getAnnotation(Id.class);columnInfo.setIsId(id != null);return columnInfo;}return null;		}private ColumnInfo getColumnFromMethod(Method method){String methodName;String fieldGetName;ColumnInfo columnInfo;fieldGetName=methodName=method.getName();if (methodName.startsWith("get")){fieldGetName=methodName.substring(3);}else if (methodName.startsWith("is")){fieldGetName=methodName.substring(2);}fieldGetName=fieldGetName.substring(0,1).toLowerCase()+fieldGetName.substring(1);String fieldName=fieldGetName;Column column = method.getAnnotation(Column.class);Class<?> type=method.getReturnType();if (column != null){columnInfo=new ColumnInfo(fieldName, column.table(), column.name(),  type,java.sql.Types.NULL);ConditionColumn filter=method.getAnnotation(ConditionColumn.class);if (filter!=null){columnInfo.setFilterName(filter.filterName());}return columnInfo;}else{return null;}}private void createSelectSQL(){if (dataObjectType==BeanMappingType.Select){checkSQL();return;}StringBuffer selectFrom=new StringBuffer("select ");columns.forEach((field,column)->selectFrom.append(column.getColumnName()).append(","));selectFrom.replace(selectFrom.length()-1, selectFrom.length(), " ");selectSQL =selectFrom.append("\r\n from ").append(tableName).toString();} private void checkSQL(){int[] indexes=SqlUtil.indexAllOfKeywordInSql(selectSQL, "select");if (indexes.length!=1){throw new RuntimeException("暂时不支持Union功能 ，selectSQL只能包含了1个select,selectSQL:"+selectSQL);}indexes=SqlUtil.indexAllOfKeywordInSql(selectSQL, "from");if (indexes.length!=1){throw new RuntimeException("暂时不支持Union功能 ，selectSQL只能包含了1个from,selectSQL:"+selectSQL);}}private void createCountSQL(){		if (dataObjectType==BeanMappingType.Select){checkSQL();return;}countSQL ="select count(*) \r\n from "+tableName;}private void createInsertSQL(){if (dataObjectType==BeanMappingType.Select){return ;}StringBuffer fields=new StringBuffer();StringBuffer values=new StringBuffer();Iterator<Entry<String,ColumnInfo>> colInfos=columns.entrySet().iterator();ColumnInfo column;for (int i=0;colInfos.hasNext();i++){column=colInfos.next().getValue();String columnName=column.getColumnName();if (columnName == null || columnName.length() == 0)continue;if (i>0){fields.append(",");values.append(",");}fields.append(column.getColumnName());values.append("#{entityBean.").append(column.getFieldName()).append("}");}insertSQL="insert into "+tableName+" ("+fields+") values ("+values+")";}private void createExistSQL(){StringBuffer existSql=new StringBuffer();existSql.append(" select count(*) from ").append(tableName).append(" where ");		int i=0;for(ColumnInfo col:IdColumns){if (i>0)existSql.append(" and ");existSql.append(col.getColumnName()).append(" = #{entityBean.").append(col.getFieldName()).append("}");	i++;}this.existSQL=existSql.toString();}private void createDeleteSQL(){if (dataObjectType==BeanMappingType.Select){return ;}StringBuffer dltSql=new StringBuffer();dltSql.append("delete from ").append(tableName).append(" where ");int i=0;for(ColumnInfo col:IdColumns){if (i>0)dltSql.append(" and ");dltSql.append(col.getColumnName()).append(" = #{entityBean.").append(col.getFieldName()).append("}");	i++;}this.deleteSQL=dltSql.toString();}private void createUpdateSQL(){if (dataObjectType==BeanMappingType.Select){return ;}StringBuffer updtSql=new StringBuffer();updtSql.append("update ").append(tableName).append(" set ");int i=0;String columnName;ColumnInfo column;for (Entry<String,ColumnInfo> colEntry:columns.entrySet()){column=colEntry.getValue();columnName=column.getColumnName();if (columnName == null || columnName.length() == 0)continue;if (column.getIsId())continue;if (i>0)updtSql.append(",");updtSql.append(column.getColumnName()).append(" = #{entityBean.").append(column.getFieldName()).append("}");i++;}i=0;updtSql.append(" where ");for(ColumnInfo col:IdColumns){if (i>0)updtSql.append(" and ");updtSql.append(col.getColumnName()).append(" = #{entityBean.").append(col.getFieldName()).append("}");	i++;}this.updateSQL=updtSql.toString();}private void createSaveSQL(){if (dataObjectType==BeanMappingType.Select){return ;}StringBuffer fields=new StringBuffer();StringBuffer values=new StringBuffer();Iterator<Entry<String,ColumnInfo>> colInfos=columns.entrySet().iterator();ColumnInfo column;for (int i=0;colInfos.hasNext();i++){column=colInfos.next().getValue();String columnName=column.getColumnName();if (columnName == null || columnName.length() == 0)continue;if (i>0){fields.append(",");values.append(",");}fields.append(column.getColumnName());values.append("#{entityBean.").append(column.getFieldName()).append("}");}StringBuffer savesql=new StringBuffer();savesql.append("insert into ").append(tableName).append(" (").append(fields).append(") values (").append(values).append(") ON DUPLICATE KEY UPDATE ");int i=0;String columnName;for (Entry<String,ColumnInfo> colEntry:columns.entrySet()){column=colEntry.getValue();columnName=column.getColumnName();if (columnName == null || columnName.length() == 0)continue;if (column.getIsId())continue;if (i>0)savesql.append(",");savesql.append(column.getColumnName()).append(" = #{entityBean.").append(column.getFieldName()).append("}");i++;}this.saveSQL=savesql.toString();}private void createGetByIdSQL(){if (dataObjectType==BeanMappingType.Select){return ;}StringBuffer getSql=new StringBuffer();getSql.append("select * from ").append(tableName).append(" where ");int i=0;for(ColumnInfo col:IdColumns){if (i>0)getSql.append(" and ");getSql.append(col.getColumnName()).append(" = #{entityId.").append(col.getFieldName()).append("}");	i++;}this.getByIdSQL=getSql.toString();}public String getSelectFrom(){return selectSQL;}public String getTableName() {return tableName;}public void setTableName(String tableName) {this.tableName = tableName;}public String getSelectSQL() {return selectSQL;}public void setSelectSQL(String selectString) {this.selectSQL = selectString;}……(略去部分)@Overridepublic Iterator<Entry<Class<?>, EntityBeanInfo>> iterator() {return entityBeanInfos.entrySet().iterator();	} 
}

2. ColumnInfo类

public class ColumnInfo {private String fieldName;private boolean isId=false;private String tableName;//结果集字段名private String columnName;//条件字段名private String filterName;private boolean filterable=true;private Class<?> javaType;private int jdbcType;public ColumnInfo(String fieldName, String tableName, String columnName, Class<?> javaType,int jdbcType){this.fieldName=fieldName;this.tableName=tableName;this.columnName=columnName;this.javaType=javaType;this.jdbcType=jdbcType;if (this.columnName==null || this.columnName.trim().length()==0){this.columnName=this.fieldName;}filterName=this.columnName;}public String getFieldName() {return fieldName;}public void setFieldName(String fieldName) {this.fieldName = fieldName;}public boolean getIsId() {return isId;}public void setIsId(boolean isId) {this.isId = isId;}public String getTableName() {return tableName;}public void setTableName(String tableName) {this.tableName = tableName;}……(略去部分)}

D. 扩展ExecutorInterceptor。

对于分页查询，需要提供数据库端分页，同时获取满足条件的数据行数，需要分两次执行，第一次执行select count(*) from ……,获得记录数后，再执行select …… from ……获取查询记录，因此定义一个PagedExecutorInterceptor，截获掉框架的Executor，分两次调用Executor的query方法，并组装成分页数据，返回给调用者。

PagedExecutorInterceptor类代码：

@Service
@Intercepts({ @Signature(type = Executor.class, method = "query", args = {  MappedStatement.class, Object.class, RowBounds.class,  ResultHandler.class }) })  
public class PagedExecutorInterceptor implements Interceptor {private final Logger logger = LoggerFactory.getLogger(this.getClass());static int MAPPED_STATEMENT_INDEX = 0;  static int PARAMETER_INDEX = 1;  static int ROWBOUNDS_INDEX = 2;  static int RESULT_HANDLER_INDEX = 3;  IDialect dialect=new MySQLDialect();  private Properties properties;public Object intercept(Invocation invocation) throws Throwable {  Object[] queryArgs = invocation.getArgs();Object parameter = queryArgs[PARAMETER_INDEX];  Paginate<?> paginate=getPaginate((HashMap<String,Object>)parameter);if (paginate != null && parameter instanceof HashMap ){return execute(invocation,queryArgs,paginate);    }return invocation.proceed();     }  protected Object execute(Invocation invocation,Object[] queryArgs,Paginate<?> paginate) throws Throwable{MappedStatement ms = (MappedStatement) queryArgs[MAPPED_STATEMENT_INDEX];List<ResultMap> resultMaps=ms.getResultMaps();int paginateIndex=getIndexInResultMap(resultMaps,Paginate.class);Object parameter = queryArgs[PARAMETER_INDEX];  BoundSql boundSql = ms.getBoundSql(parameter);  String sql = boundSql.getSql().trim();  HashMap<String,Object>  params=(HashMap<String,Object>) parameter;Class<?> beanClass=(Class<?>)params.get("entityClass");// 获取统计行数String cntSql=getRowCountSQL(sql);processIntercept(boundSql,queryArgs, paginate, Integer.class, paginateIndex, cntSql);Object rowCount = invocation.proceed();if (rowCount instanceof List) {List<Integer> rows = (List<Integer>) rowCount;int totalRows = rows.get(0);paginate.setTotalRows(totalRows);int totalPages = (totalRows + paginate.getPageSize() - 1) / paginate.getPageSize();paginate.setTotalPages(totalPages);}//获取分页数据String pagedSql=getPagedSQL(sql,paginate);processIntercept(boundSql,queryArgs,paginate,beanClass,paginateIndex,pagedSql);  Object rows=invocation.proceed();paginate.setDatas((List)rows);List result=new ArrayList();result.add(paginate);return result;}/*** 获取生成行数sql，本方法只是简单找到FROM位置和order by 位置。* 暂时不支持对 包含union 字句的功能,支持包含有子查询的sql* @param sql* @return*/protected String getRowCountSQL(String sql){int selectPos=SqlUtil.indexOfKeywordInSql(sql, "select");int[] fromPoses=SqlUtil.indexAllOfKeywordInSql(sql, "from");String lowsql=sql.toLowerCase();String cntSql="select count(*) from ";if (fromPoses.length==1){int orderPos = lowsql.indexOf("order ",fromPoses[0]);if (orderPos>0)cntSql=sql.substring(0,selectPos)+cntSql+sql.substring(fromPoses[0]+5,orderPos);elsecntSql=sql.substring(0,selectPos)+cntSql+sql.substring(fromPoses[0]+5);}else{cntSql=cntSql+"("+sql+") as t";}logger.debug("mybatis get rowCount sql:{}", cntSql);return cntSql;}protected String getPagedSQL(String sql,Paginate<?> paginate){String slctSql=sql;if (paginate.getPageNo() < 1) {paginate.setPageNo(1);}int offset = (paginate.getPageNo() - 1) * paginate.getPageSize();int limit = paginate.getPageSize();if (dialect.supportsLimitOffset()) {  slctSql = dialect.getLimitString(slctSql, offset, limit);  } else {  slctSql = dialect.getLimitString(slctSql, 0, limit);  }logger.debug("mybatis pagedQuery sql:{}", slctSql);return slctSql;}protected void processIntercept(BoundSql boundSql,final Object[] queryArgs,Paginate<?> paginate,Class<?> type,int index,String sql) {  MappedStatement ms = (MappedStatement) queryArgs[MAPPED_STATEMENT_INDEX];  final RowBounds rowBounds = (RowBounds) queryArgs[ROWBOUNDS_INDEX];  if (dialect.supportsLimit() ) {  MappedStatement newMs = createMappedStatement(type,index,ms,sql,boundSql);  queryArgs[MAPPED_STATEMENT_INDEX] = newMs;                          queryArgs[ROWBOUNDS_INDEX]=new PagedRowBounds(type,paginate, rowBounds);}}  private Paginate<?> getPaginate(HashMap<String,Object> params){for (Map.Entry<String, Object> param : params.entrySet()) {if (param.getValue() instanceof Paginate)return (Paginate) param.getValue();}    		return null;}private int getIndexInResultMap(List<ResultMap> resultMaps,Class<?> type){ResultMap rm;Class<?> entityClass;for(int i=0;i<resultMaps.size();i++){rm=resultMaps.get(i);entityClass=rm.getType();if (entityClass.equals(type)){return i;}        	}return -1;}private MappedStatement createMappedStatement(Class<?> beanClass,int index,MappedStatement ms,String sql,BoundSql boundSql){BoundSql newBoundSql = new PagedBoundSql(beanClass,ms.getConfiguration(), sql,  boundSql.getParameterMappings(),  boundSql.getParameterObject());  MappedStatement newMs =InterceptorUtil.copyFromMappedStatement(beanClass,index,ms,   new BoundSqlSqlSource(newBoundSql));  return newMs;}public Object plugin(Object target) {  return Plugin.wrap(target, this);  }  public void setProperties(Properties properties) {  this.properties = properties; }  }

如何使用

只需要写好EntityBean，Mapper只需要扩展GenericMapper，就可以调用基类接口中的方法了。
1.定义个EntityBean或者定义一个查询Bean

先来个实体bean

@Entity
@Table(name = "AppInfo")
public class AppInfo {@Idprivate String appId;private String name;……(部分省略)public String getAppId() {return appId;}public void setAppId(String appId) {this.appId = appId;}public String getName() {return name;}public void setName(String name) {this.name = name;}……(部分省略)
}

再来个查询bean

@Entity
@BeanSQLMap(mappingSQL = "select d.*,c.name as confName,c.value as configValue "+ "from RfcServiceDef d join RfcServiceConfig c on d.id=c.serviceId ",countSQL = "select count(*) "+ "from RfcServiceDef d join RfcServiceConfig c on d.id=c.serviceId ")
public class RfcServiceAndConfig {private int id;private String name;……(部分省略)@Column(name="confName")@ConditionColumn(filterName="c.name")private String confName;@Column(name="configValue")@ConditionColumn(filterName="c.value")private String configValue;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getConfName() {return confName;}public void setConfName(String confName) {this.confName = confName;}public String getConfigValue() {return configValue;}public void setConfigValue(String configValue) {this.configValue = configValue;}
}

2.继承扩展一下GenericMapper

@Mapper
public interface AppInfoMapper extends GenericMapper<AppInfo> {
}

@Mapper
public interface RfcServiceAndConfigMapper extends GenericMapper<RfcServiceAndConfig> {}

现在，你不用写基类方法，也不用配XML，就可以使用了，下面来个例子。

	@Autowiredprivate AppInfoMapper appInfoMapper;@AutowiredRfcServiceAndConfigMapper rfcServiceAndConfigMapper;……(部分省略)Map<String,Object> paras=new HashMap<>(); 
paras.put("appId_like","2019");
paras.put("name","零售抽奖");
List<AppInfo> result =appInfoMapper.query(AppInfo.class, paras);
……(部分省略)
Map<String,Object> paras=new HashMap<>(); 
paras.put("chnName_like", "会员");
Paginate<RfcServiceAndConfig> paginate=new Paginate<>();
paginate.setPageNo(2);
paginate.setPageSize(10);
Paginate<RfcServiceAndConfig> result = rfcServiceAndConfigMapper.pagedQuery(RfcServiceAndConfig.class,paginate, paras,"");

写在后面

通过粗浅的学习了解，个人觉得：
１．Hibernate学习的成本比Mybatis大，特别是他基于对象的视角看待数据，表与表数据关系体现为实体数据间关系，数据操作主要采用Hql，要掌握Hql，需要开发人员从对象及对象关系的视角重新审视SQL，对开发人员OOP的能力要求稍微更高一些。
２．Mybatis主要以手动编写SQL语句以及ResultMap的方式使用，重点关注在数据上。而Hibernate映射机制封装度的抽象层级更高，开发人员不需要关心SQL的生成与结果映射，让开发人员更专注于业务流程和数据关系上。
３. 相比Hibernate来看，Mybatis还是要简陋一些，在持久化层要低一些。Mybatis宣称让开发人员可以自由写SQL，成为他流行的两点，降低开发人员门槛，也就降低了开发的成本。当然使用Hibernate，如果遇到性能问题时一样可以直接使用SQL，这在以前的Hibernate项目中依然将SQL作为性能调优的强有力的手段。
４．Hibernate的HQL语句与具体使用的数据库无关，移植性很好。MyBatis项目中所有的SQL语句都是依赖所用的数据库的，所以数据库移植的支持度相对差。

这只是个人的一些使用体会，不是为了评价或测评这两个框架的优缺点，当然也不是为了挑起两大阵营间的论战，这不是我的初衷。
再有就是，由于使用还没有三周，一定会有很多地方理解错误，或者使用上的错误，还望不吝赐教，批评指正。