Mybatis框架中Interceptor接口的使用说明
Mybatis Interceptor接口的使用
关于Mybatis中插件的声明需要在configuration的配置文件中进行配置，配置文件的位置使用configLocation属性指定。
测试中使用的config文件内容如下
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--plugins插件之 分页拦截器 -->
<plugins>
<plugin interceptor="com.interceptors.LogInterceptor" ></plugin>
</plugins>
</configuration>
在配置文件中配置了一个Interceptor的实现类
LogInterceptor的代码如下：
public class LogInterceptor implements Interceptor{
@Override
public Object intercept(Invocation invocation) throws Throwable {
System.out.println("LogInterceptor : intercept");
return null;
}
@Override
public Object plugin(Object target) {
if(target instanceof StatementHandler){
RoutingStatementHandler handler = (RoutingStatementHandler)target;
//打印出当前执行的sql语句
System.out.println(handler.getBoundSql().getSql());
}
return target;
}
@Override
public void setProperties(Properties properties) {
System.out.println("LogInterceptor : setProperties");
}
}
在工程的配置文件中，在配置SqlSessionFactoryBean时需要指明config配置文件的位置，配置文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
<bean id="user1" class="com.beans.User">
<property name="userName" value="zhuyuqiang"/>
</bean>
<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
<property name="name" value="mysql"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/world"/>
<property name="username" value="root"/>
<property name="password" value="zh4y4q5ang"/>
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
</bean>
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="mapperLocations" value="classpath:mybatis/*.xml"/>
<property name="typeAliasesPackage" value="com.entities"/>
<property name="configLocation" value="classpath:config/configuration.xml"/>
</bean>
<bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.interfaces"/>
</bean>
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<context:component-scan base-package="com"/>
</beans>
基本上这样配置以后，在工程中声明的plugin就已经生效了，实际中打印出来的log如下：
SELECT * FROM city WHERE ID=?
执行的CityMapper如下：
<?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.interfaces.CityMapper">
<resultMap id="BaseResultMap" type="com.entities.City">
<id column="ID" jdbcType="INTEGER" property="id"/>
<result column="Name" jdbcType="CHAR" property="name"/>
<result column="CountryCode" jdbcType="CHAR" property="countrycode"/>
<result column="District" jdbcType="CHAR" property="district"/>
<result column="Population" jdbcType="INTEGER" property="population"/>
</resultMap>
<select id="selectCityById" parameterType="int" resultType="com.entities.City">
SELECT * FROM city WHERE ID=#{id,jdbcType=INTEGER}
</select>
</mapper>
简单的测试了一下，可以打印出sql语句。在使用mybatis提供的plugin接口时需要注意，在构建ParameterHandler 、ResultSetHandler 、StatementHandler 和Executor 的时候都会调用在项目中实现的插件接口，一般情况下，如果只是为了打印显示当前执行的sql语句，可以只在当target为StatementHandler类型的时候再进行处理即可。
public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
return parameterHandler;
}
public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, RowBounds rowBounds, ParameterHandler parameterHandler,
ResultHandler resultHandler, BoundSql boundSql) {
ResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, mappedStatement, parameterHandler, resultHandler, boundSql, rowBounds);
resultSetHandler = (ResultSetHandler) interceptorChain.pluginAll(resultSetHandler);
return resultSetHandler;
}
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
System.out.println("newStatementHandler......");
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
return statementHandler;
}
public Executor newExecutor(Transaction transaction) {
return newExecutor(transaction, defaultExecutorType);
}
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
executorType = executorType == null ? defaultExecutorType : executorType;
executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
Executor executor;
if (ExecutorType.BATCH == executorType) {
executor = new BatchExecutor(this, transaction);
} else if (ExecutorType.REUSE == executorType) {
executor = new ReuseExecutor(this, transaction);
} else {
executor = new SimpleExecutor(this, transaction);
}
if (cacheEnabled) {
executor = new CachingExecutor(executor);
}
executor = (Executor) interceptorChain.pluginAll(executor);
return executor;
}
在实际测操作中，在项目中定义实现的plugin都会被添加保存到interceptorChain对象的一个集合中，在内部会对集合里的对象进行遍历，分别调用每个插件的plugin方法。
其中target就是在调用pluginAll传入的具体对象。。。
Interceptor修改执行sql及传入参数
项目中途遇到业务需求更改，在查询某张表时需要增加条件，由于涉及的sql语句多而且依赖其他服务的jar，逐个修改sql语句和接口太繁杂。项目使用mybatis框架，因此借鉴PageHelper插件尝试使用mybatis的Interceptor来实现改需求。
总体思路
- 从BoundSql中获取sql，通过正则匹配替换表名为子查询REPLACE_TXT
- 添加子查询REPLACE_TXT 中需要用到的参数到mybatis参数列表中
- 添加参数与占位符映射，即添加ParameterMapping对象到ParameterMappings中，由于statement在执行时是按照ParameterMappings的元素索引定位占位符封装参数（即ParameterMappings中的第一个参数会封装到第一个占位符上），因此ParameterMappings中的参数顺序需要和占位符保持一致。其次ParameterMappings的元素个数需要和占位符个数保持一致。
- 为了保证该intercept在最后执行，使用AutoConfiguration将intercept添加到SqlSessionFactory的Configuration中，并在spring.factories文件中添加AutoConfiguration
- 未测试性能以及是否存在未知缺陷
1、Interceptor 代码实现
package org.cnbi.project.other.sql.intercept;
import cn.hutool.core.util.NumberUtil;
import com.cnbi.cloud.common.core.exception.ServiceException;
import com.github.pagehelper.Page;
import com.github.pagehelper.util.ExecutorUtil;
import com.github.pagehelper.util.MetaObjectUtil;
import org.apache.ibatis.builder.annotation.ProviderSqlSource;
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.mapping.ParameterMapping;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.cnbi.project.other.sql.aop.PeriodHolder;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* @ClassName ParamInterceptor
* @Description 修改接口太繁琐，直接用mybatis拦截器对查询sql进行拦截，将期间参数注入sql
* @Author Wangjunkai
* @Date 2019/10/23 11:36
**/
@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 ParamInterceptor implements Interceptor {
private final static Pattern DW_DIMCOMPANY = Pattern.compile("dw_dimcompany", Pattern.CASE_INSENSITIVE);
private final static String REPLACE_TXT = "(select * from dw_dimcompany where cisdel = '0' and START_PERIOD <= ? and END_PERIOD > ?)";
@Override
public Object intercept(Invocation invocation) throws Throwable {
Object[] args = invocation.getArgs();
MappedStatement ms = (MappedStatement) args[0];
Object parameter = args[1];
RowBounds rowBounds = (RowBounds) args[2];
ResultHandler resultHandler = (ResultHandler) args[3];
Executor executor = (Executor) invocation.getTarget();
CacheKey cacheKey;
BoundSql boundSql;
if(args.length == 4){
boundSql = ms.getBoundSql(parameter);
} else {
boundSql = (BoundSql) args[5];
}
//获取sql语句，使用正则忽略大小写匹配
String sql = boundSql.getSql();
Matcher matcher = DW_DIMCOMPANY.matcher(sql);
//没有需要替换的表名则放行
if(!matcher.find()){
return invocation.proceed();
}
//收集占位符个数（即paramIndex 的size）以及占位符次序（slot：即参数在ParameterMappings中的顺序）
int index = 0;
ArrayList<Integer> paramIndex = new ArrayList<>();
while(matcher.find(index)){
index = matcher.end();
String sqlPart = sql.substring(0, index);
int slot = index - sqlPart.replace("?", "").length() + paramIndex.size() ;
paramIndex.add(slot);
paramIndex.add(slot + 1);
}
//替换子查询
String companyPeriodSql = matcher.replaceAll(REPLACE_TXT);
cacheKey = args.length == 4 ? executor.createCacheKey(ms, parameter, rowBounds, boundSql) : (CacheKey) args[4];
//处理参数
Object parameterObject = processParameterObject(ms, parameter, boundSql, cacheKey, paramIndex);
BoundSql companyPeriodBoundSql = new BoundSql(ms.getConfiguration(), companyPeriodSql, boundSql.getParameterMappings(), parameterObject);
Map<String, Object> additionalParameters = ExecutorUtil.getAdditionalParameter(boundSql);
//设置动态参数
for (String key : additionalParameters.keySet()) {
companyPeriodBoundSql.setAdditionalParameter(key, additionalParameters.get(key));
}
return executor.query(ms, parameterObject, RowBounds.DEFAULT, resultHandler, cacheKey, companyPeriodBoundSql);
}
public Object processParameterObject(MappedStatement ms, Object parameterObject, BoundSql boundSql, CacheKey pageKey, ArrayList<Integer> paramIndex) {
//处理参数
Map<String, Object> paramMap = null;
if (parameterObject == null) {
paramMap = new HashMap<>();
} else if (parameterObject instanceof Map) {
//解决不可变Map的情况
paramMap = new HashMap<>();
paramMap.putAll((Map) parameterObject);
} else {
paramMap = new HashMap<>();
// sqlSource为ProviderSqlSource时，处理只有1个参数的情况
if (ms.getSqlSource() instanceof ProviderSqlSource) {
String[] providerMethodArgumentNames = ExecutorUtil.getProviderMethodArgumentNames((ProviderSqlSource) ms.getSqlSource());
if (providerMethodArgumentNames != null && providerMethodArgumentNames.length == 1) {
paramMap.put(providerMethodArgumentNames[0], parameterObject);
paramMap.put("param1", parameterObject);
}
}
//动态sql时的判断条件不会出现在ParameterMapping中，但是必须有，所以这里需要收集所有的getter属性
//TypeHandlerRegistry可以直接处理的会作为一个直接使用的对象进行处理
boolean hasTypeHandler = ms.getConfiguration().getTypeHandlerRegistry().hasTypeHandler(parameterObject.getClass());
MetaObject metaObject = MetaObjectUtil.forObject(parameterObject);
//需要针对注解形式的MyProviderSqlSource保存原值
if (!hasTypeHandler) {
for (String name : metaObject.getGetterNames()) {
paramMap.put(name, metaObject.getValue(name));
}
}
//下面这段方法，主要解决一个常见类型的参数时的问题
if (boundSql.getParameterMappings() != null && boundSql.getParameterMappings().size() > 0) {
for (ParameterMapping parameterMapping : boundSql.getParameterMappings()) {
String name = parameterMapping.getProperty();
if (!name.equals(GLOBALPERIOD)
&& paramMap.get(name) == null) {
if (hasTypeHandler
|| parameterMapping.getJavaType().equals(parameterObject.getClass())) {
paramMap.put(name, parameterObject);
break;
}
}
}
}
}
return processPageParameter(ms, paramMap, boundSql, pageKey, paramIndex);
}
private final static String GLOBALPERIOD = "globalPeriod";
public Object processPageParameter(MappedStatement ms, Map<String, Object> paramMap, BoundSql boundSql, CacheKey pageKey, ArrayList<Integer> paramIndex) {
paramMap.put(GLOBALPERIOD, getPeriod());
//处理pageKey
pageKey.update(getPeriod());
//处理参数配置
handleParameter(boundSql, ms, paramIndex);
return paramMap;
}
protected void handleParameter(BoundSql boundSql, MappedStatement ms, ArrayList<Integer> paramIndex) {
if (boundSql.getParameterMappings() != null) {
List<ParameterMapping> newParameterMappings = new ArrayList<>(boundSql.getParameterMappings());
for (Integer index : paramIndex) {
if(index < newParameterMappings.size()) {
newParameterMappings.add(index, new ParameterMapping.Builder(ms.getConfiguration(), GLOBALPERIOD, String.class).build());
}else{
newParameterMappings.add(new ParameterMapping.Builder(ms.getConfiguration(), GLOBALPERIOD, String.class).build());
}
}
MetaObject metaObject = MetaObjectUtil.forObject(boundSql);
metaObject.setValue("parameterMappings", newParameterMappings);
}
}
private final static String Q = "Q";
private final static String H = "H";
private String getPeriod(){
//使用threadlocal保存从request中获取的参数，此处不再描述
String period = PeriodHolder.getPeriod();
if(NumberUtil.isNumber(period)){
return period;
}else if(period.contains(Q)){
return period.substring(0, 4) + Integer.parseInt(period.substring(5)) * 3;
}else if(period.contains(H)){
return period.substring(0, 4) + Integer.parseInt(period.substring(5)) * 6;
}else{
throw new ServiceException("非法期间:" + period);
}
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
@Override
public void setProperties(Properties properties) {
//nothing to do...
}
}
2、AutoConfiguration代码实现
package org.cnbi.project.autoconfig;
import com.github.pagehelper.autoconfigure.PageHelperAutoConfiguration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.cnbi.project.other.sql.intercept.ParamInterceptor;
import org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.context.annotation.Configuration;
import javax.annotation.PostConstruct;
import java.util.Iterator;
import java.util.List;
/**
* @ClassName ParamIntecepterAutoConfiguration
* @Description
* @Author Wangjunkai
* @Date 2019/10/23 15:41
**/
@AutoConfigureAfter({MybatisAutoConfiguration.class, PageHelperAutoConfiguration.class})
@Configuration
public class ParamIntecepterAutoConfiguration {
@Autowired
private List<SqlSessionFactory> sqlSessionFactoryList;
public ParamIntecepterAutoConfiguration() {
}
@PostConstruct
public void addParamInterceptor() {
ParamInterceptor interceptor = new ParamInterceptor();
Iterator var3 = this.sqlSessionFactoryList.iterator();
while(var3.hasNext()) {
SqlSessionFactory sqlSessionFactory = (SqlSessionFactory)var3.next();
sqlSessionFactory.getConfiguration().addInterceptor(interceptor);
}
}
}
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。