typeHandler
typeHandler有什么用？
你可以重寫類型處理器或創建你自己的類型處理器來處理不支持的或非標準的類型。 具體做法為：實現 org.apache.ibatis.type.TypeHandler 接口， 或繼承一個很便利的類 org.apache.ibatis.type.BaseTypeHandler， 然后可以選擇性地將它映射到一個 JDBC 類型
用法
參考官網的示例：
package com.xh.mybatisLearn.utils;import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;
import org.apache.ibatis.type.MappedTypes;import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;/*** Created by root on 3/2/18.*/
@MappedJdbcTypes(JdbcType.VARCHAR)
@MappedTypes(String.class)
public class ExampleTypeHandler extends BaseTypeHandler<String> {public void setNonNullParameter(PreparedStatement preparedStatement, int i, String s, JdbcType jdbcType) throws SQLException {preparedStatement.setString(i, "in>>" + s);}public String getNullableResult(ResultSet resultSet, String s) throws SQLException {return resultSet.getString(s);}public String getNullableResult(ResultSet resultSet, int i) throws SQLException {return resultSet.getString(i);}public String getNullableResult(CallableStatement callableStatement, int i) throws SQLException {return callableStatement.getString(i);}
}
注冊TypeHandler
<typeHandlers><typeHandler handler="com.xh.mybatisLearn.utils.ExampleTypeHandler"/></typeHandlers>插入時指定TypeHandler
<insert id="addUser" useGeneratedKeys="true"keyProperty="id">insert into user_tb (username,age) VALUES (#{username,typeHandler=com.xh.mybatisLearn.utils.ExampleTypeHandler},#{age})</insert>
結果：
getAll>>User{id=17, username='in>>u1', age=21}plugin
plugin有什么用？
MyBatis 允許你在已映射語句執行過程中的某一點進行攔截調用。默認情況下，MyBatis 允許使用插件來攔截的方法調用包括：
Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)
ParameterHandler (getParameterObject, setParameters)
ResultSetHandler (handleResultSets, handleOutputParameters)
StatementHandler (prepare, parameterize, batch, update, query)
用法
通過 MyBatis 提供的強大機制，使用插件是非常簡單的，只需實現 Interceptor 接口，并指定了想要攔截的方法簽名即可。
參考官網示例：
package com.xh.mybatisLearn.utils;import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.util.Properties;/*** Created by root on 3/2/18.*/
@Intercepts({@Signature(type = Executor.class,method = "query",args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})})
public class ExamplePlugin implements Interceptor {private final Logger logger = LoggerFactory.getLogger(ExamplePlugin.class);public Object intercept(Invocation invocation) throws Throwable {MappedStatement ms = (MappedStatement) invocation.getArgs()[0];BoundSql boundSql = ms.getBoundSql(invocation.getArgs()[1]);logger.info("==================== sql:{}", boundSql.getSql());return invocation.proceed();}public Object plugin(Object target) {return Plugin.wrap(target, this);}public void setProperties(Properties properties) {String some_string = properties.getProperty("some_string");logger.info("==================== some_string:{}", some_string);}
}這個插件就是打印查詢的sql，
其中type對應：
Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)
ParameterHandler (getParameterObject, setParameters)
ResultSetHandler (handleResultSets, handleOutputParameters)
StatementHandler (prepare, parameterize, batch, update, query)
method對應：上面各項括號的方法
args對應：method的參數
plugin注冊
<plugins><plugin interceptor="com.xh.mybatisLearn.utils.ExamplePlugin"><property name="some_string" value="some_string_xxxxxx"/></plugin></plugins>logger
<dependency><groupId>org.slf4j</groupId><artifactId>slf4j-simple</artifactId><version>1.7.21</version></dependency>輸出
[main] INFO com.xh.mybatisLearn.utils.ExamplePlugin - ==================== some_string:some_string_xxxxxx
[main] INFO com.xh.mybatisLearn.utils.ExamplePlugin - ==================== sql:select * from user_tb where id=?
getOne>>User{id=12, username='u1', age=21}
)
)
