今天学了点Mybatis拦截器，参考了Mybatis-Plus部分代码
首先是使用@Intercepts注解，它的源码注释告诉我们可以这样使用：
mybatis-plus中使用的就是这种方式，参考：
这里可以传入@Signature，指定它的type为：
Executor，执行器，我们可以看到它包含了如下方法，说明它是一个比较全能的范围，可以做很多事情参数如处理、返回处理、重写sql等
我们依葫芦画瓢写两个：
代码语言：javascript复制package com.ruben.simplescaffold.plugin;
import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.lang.Opt;
import cn.hutool.core.util.StrUtil;
import com.baomidou.mybatisplus.core.enums.SqlKeyword;
import com.ruben.simplescaffold.entity.UserDetail;
import org.apache.ibatis.cache.CacheKey;
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.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.springframework.stereotype.Component;
import java.lang.reflect.Method;
import java.util.ArrayList;
/**
* @author <achao1441470436@gmail.com>
* @since 2022/4/10 13:54
*/
@Component
@Intercepts(
{
@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class, CacheKey.class, BoundSql.class}),
}
)
public class MybatisExecutorQueryPlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
Executor executor = (Executor) invocation.getTarget();
Object[] args = invocation.getArgs();
Method method = invocation.getMethod();
MappedStatement ms = (MappedStatement) args[0];
Object parameter = args[1];
BoundSql boundSql;
if (args.length == 4) {
boundSql = ms.getBoundSql(parameter);
} else {
boundSql = (BoundSql) args[5];
}
// 反射工具类，可以修改sql语句等
MetaObject metaObject = SystemMetaObject.forObject(boundSql);
String sql = (String) metaObject.getValue("sql");
if (!StrUtil.containsIgnoreCase(sql, SqlKeyword.ORDER_BY.getSqlSegment())) {
// 更改sql
metaObject.setValue("sql", sql " order by id asc");
}
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
}写完了查询，再写一个更新的
代码语言：javascript复制package com.ruben.simplescaffold.plugin;
import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.lang.func.Func1;
import cn.hutool.core.lang.func.LambdaUtil;
import cn.hutool.core.util.ReflectUtil;
import com.baomidou.mybatisplus.core.conditions.AbstractWrapper;
import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.conditions.update.Update;
import com.baomidou.mybatisplus.core.exceptions.MybatisPlusException;
import com.baomidou.mybatisplus.core.mapper.Mapper;
import com.baomidou.mybatisplus.core.metadata.TableFieldInfo;
import com.baomidou.mybatisplus.core.metadata.TableInfoHelper;
import com.baomidou.mybatisplus.core.toolkit.Constants;
import com.baomidou.mybatisplus.core.toolkit.ReflectionKit;
import com.baomidou.mybatisplus.core.toolkit.Wrappers;
import com.ruben.simplescaffold.entity.UserDetail;
import com.ruben.simplescaffold.pojo.common.BaseEntity;
import lombok.extern.slf4j.Slf4j;
import org.apache.http.Consts;
import org.apache.ibatis.binding.MapperMethod;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.springframework.stereotype.Component;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.time.LocalDateTime;
import java.util.List;
import java.util.Map;
import java.util.Objects;
/**
* Mybatis拦截器
*
* @author <achao1441470436@gmail.com>
* @since 2022/3/31 22:22
*/
@Component
@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})})
public class MybatisExecutorUpdatePlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
Object[] args = invocation.getArgs();
MappedStatement ms = (MappedStatement) args[0];
if (SqlCommandType.INSERT.equals(ms.getSqlCommandType())) {
// 新增
fillTime(args[1], UserDetail::getGmtCreate);
fillTime(args[1], UserDetail::getGmtModified);
}
if (SqlCommandType.UPDATE.equals(ms.getSqlCommandType()) && args[1] instanceof MapperMethod.ParamMap) {
// 更新
MapperMethod.ParamMap<?> paramMap = (MapperMethod.ParamMap<?>) args[1];
Object bean = paramMap.get(Constants.ENTITY);
if (paramMap.containsKey(Constants.WRAPPER)) {
// 通过Wrapper更新
Object wrapper = paramMap.get(Constants.WRAPPER);
if (wrapper instanceof AbstractWrapper && wrapper instanceof Update) {
String fieldName = LambdaUtil.getFieldName(UserDetail::getGmtModified);
String mapperClassName = ms.getId().substring(0, ms.getId().lastIndexOf('.'));
Class<?> entityClass = ReflectionKit.getSuperClassGenericType(Class.forName(mapperClassName), Mapper.class, 0);
List<TableFieldInfo> fieldList = TableInfoHelper.getTableInfo(entityClass).getFieldList();
String columnName = fieldList.stream().filter(fieldInfo -> fieldInfo.getProperty().equals(fieldName)).findAny().map(TableFieldInfo::getColumn).orElseThrow(() -> new MybatisPlusException("未找到字段" fieldName));
final Map<String, Object> paramNameValuePairs = ((AbstractWrapper<?, ?, ?>) wrapper).getParamNameValuePairs();
String placeholder = "#" fieldName "#";
paramNameValuePairs.put(placeholder, LocalDateTime.now());
((Update<?, ?>) wrapper).setSql(String.format("%s = #{%s.%s}", columnName, "ew.paramNameValuePairs", placeholder));
}
} else if (Objects.nonNull(bean)) {
// 通过id更新
fillTime(bean, UserDetail::getGmtModified);
}
}
return invocation.proceed();
}
/**
* 给bean填充时间
*
* @param bean 对象
* @param func 填充方法，只用于获取属性名
* @param <T> 对象类型
*/
private <T> void fillTime(Object bean, Func1<T, ?> func) {
String fieldName = LambdaUtil.getFieldName(func);
if (ReflectUtil.hasField(bean.getClass(), fieldName)) {
BeanUtil.setFieldValue(bean, fieldName, LocalDateTime.now());
}
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
}然后是指定@Signature的type为StatementHandler，也是有各种方法
我们演示一个隔离级别设置、日志打印、sql修改(此处只是取出来再设置进去，可以按需自己处理)
package com.ruben.simplescaffold.plugin;
import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.springframework.stereotype.Component;
import java.sql.Connection;
/**
* @author <achao1441470436@gmail.com>
* @since 2022/4/10 20:49
*/
@Slf4j
@Component
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class MybatisStatementHandlerPreparePlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
Object[] args = invocation.getArgs();
Connection connection = (Connection) args[0];
connection.prepareStatement("set transaction isolation level read committed");
MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
String sql = (String) metaObject.getValue("delegate.boundSql.sql");
log.info("sql: {}", sql);
metaObject.setValue("delegate.boundSql.sql", sql);
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
}然后是@Signature的type为ParameterHandler，一看名字就是用来处理参数的
简单演示下
代码语言：javascript复制package com.ruben.simplescaffold.plugin;
import cn.hutool.core.lang.func.LambdaUtil;
import cn.hutool.core.util.ReflectUtil;
import com.ruben.simplescaffold.entity.UserDetail;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.plugin.*;
import org.springframework.stereotype.Component;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
/**
* @author <achao1441470436@gmail.com>
* @since 2022/4/10 21:16
*/
@Component
@Intercepts({@Signature(type = ParameterHandler.class, method = "setParameters", args = {PreparedStatement.class})})
public class MybatisParameterHandlerSetParametersPlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
ParameterHandler parameterHandler = (ParameterHandler) invocation.getTarget();
Object[] args = invocation.getArgs();
PreparedStatement preparedStatement = (PreparedStatement) args[0];
Object parameterObject = parameterHandler.getParameterObject();
if (parameterObject instanceof UserDetail) {
ReflectUtil.setFieldValue(parameterObject, LambdaUtil.getFieldName(UserDetail::getTenantId), 1L);
}
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
}最后就是@Signature为ResultSetHandler，用于处理结果
演示这里查询过滤掉密码
代码语言：javascript复制package com.ruben.simplescaffold.plugin;
import cn.hutool.core.collection.CollUtil;
import com.ruben.simplescaffold.entity.UserDetail;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
import org.apache.ibatis.plugin.*;
import org.springframework.stereotype.Component;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
/**
* @author <achao1441470436@gmail.com>
* @since 2022/4/10 21:40
*/
@Component
@Intercepts(@Signature(type = ResultSetHandler.class, method = "handleResultSets", args = {Statement.class}))
public class MybatisResultSetHandlerHandleResultSetsPlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
List<?> resultList = (List<?>) invocation.proceed();
Object bean = CollUtil.get(resultList, 0);
if (bean instanceof UserDetail) {
@SuppressWarnings("unchecked")
ArrayList<UserDetail> userList = (ArrayList<UserDetail>) resultList;
userList.forEach(user -> user.setPassword(null));
return userList;
}
return resultList;
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
}对了，顺便一提Plugin.wrap使用动态代理的方式，对我们方法进行了代理，其中还判断了拦截器触发的时机等操作
