Mybatis框架中Interceptor接口该如何使用

Mybatis框架中Interceptor接口该如何使用，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。

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

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：

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：

                        SELECT * FROM city WHERE ID=#{id,jdbcType=INTEGER}

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 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 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 paramIndex) {        //处理参数        Map 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 paramMap, BoundSql boundSql, CacheKey pageKey, ArrayList 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 paramIndex) {        if (boundSql.getParameterMappings() != null) {            List 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})@Configurationpublic class ParamIntecepterAutoConfiguration {    @Autowired    private List 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);        }    }}

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