mybatis拦截器

mybatis拦截器基础知识

编写类继承mybatis的Interceptor接口，并实现其相关方法。mybatis的拦截器，是被动态代理类主动调用的。

intercept：在拦截时，需要执行的业务逻辑
plugin：是否代理Executor、ParameterHandler、ResultSetHandler、StatementHandler对象中的某个或某些，
如果代理，则返回相应对象的代理对象，否则返回原对象。根据类上Intercepts注解决定是否返回代理对象。
setProperties：配置时，向拦截器设置相关参数配置

Intercepts注解：设置该拦截器需要代理的类型及其方法

Signature注解：拦截哪个类的哪个方法
type参数：被代理对象类型，只能是Executor、ParameterHandler、ResultSetHandler、StatementHandler这几种的一种。
method参数：被代理对象的方法，如Executor对象的update方法
args参数：方法参数，Java是支持重载，因此需要参数和方法名才能唯一确定某类的某个方法

比如：我们需要代理Executor的query方法，而查询方法有2个，一个有（CacheKey cacheKey, BoundSql boundSql）参数一个没有，如果我们要代理的是没有这2个参数的方法，那么需要在配置中的args参数里就不写这2个参数

被代理类型执行顺序：Executor -> ParameterHandler -> ResultSetHandler -> StatementHandler

/**
* 这个示例表示该拦截器需要拦截Executor类的update和query方法
*/
@Intercepts({@Signature(type = Executor.class, method = "update", args = { MappedStatement.class, Object.class }),@Signature(type = Executor.class, method = "query", args={MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})
})
@Slf4j
public class MyBatisInterceptor implements Interceptor{@Overridepublic Object intercept(Invocation invocation) throws Throwable {//被代理对象的被代理方法参数，如Executor的update方法，那么args[0]为MappedStatement类型对象，args[1]为类型object对象//args[1]具体为什么对象呢：当前执行查询的mapper方法对应的参数及其值//如：当前我执行的是UserMapper的fundUser(@Param("user")User oneUser)，那么这里的args[1]为一个map，key为user，值为形参oneUser对应的的值Object[] args = invocation.getArgs();//return invocation.proceed();}@Overridepublic Object plugin(Object target) {return Plugin.wrap(target, this);}@Overridepublic void setProperties(Properties properties) {}
}
/**
* 向配置中添加拦截器
*/
@Configuration
public class MyBatisConfig {@Autowiredprivate SqlSessionFactory sqlSessionFactory;@PostConstructpublic void addMySqlInterceptor() {MyBatisInterceptor interceptor = new MyBatisInterceptor();sqlSessionFactory.getConfiguration().addInterceptor(interceptor);}
}

mybatis拦截器原理

https://www.jianshu.com/p/b82d0a95b2f3

mybatis拦截器结合了动态代理和责任链2个模式。

动态代理类Plugin：

实现了InvocationHandler接口。
属性为目标对象和拦截器，通过私有的构造方法初始化数据
invoke方法：调用拦截器的拦截方法。
wrap静态方法：参数为目标对象和某个拦截器，如果某拦截器上的配置适合被代理类，则返回代理类，否则返回原始类。

拦截器类Interceptor：

intercept方法：参数为Invocation，拦截器具体业务逻辑，并在合适的位置调用invocation对象的执行方法；
wrap方法：该拦截器是否适用于被代理对象，一般直接调用Plugin的wrap方法即可。

责任链类InterceptorChain：

包含一个拦截器集合，并可以向拦截器集合添加拦截器。
pluginAll方法：参数为被代理对象，遍历拦截器，并调用拦截器的wrap方法，将返回的结果作为下个拦截器调用wrap方法的参数。
假设被代理对象为A，有多个拦截器，如A1，A2，A3，且wrap都返回代理对象，那么最终的结果为A3代理了A2，A2代理了A1，A1代理了最原始的被代理对象A

被代理类信息Invocation：

里面包含被代理类型，被代理方法，方法参数，以及一个执行方法（通过反射的方式调用被代理类的被代理方法）。
被代理类可能是最原始的被代理对象，也可能是另外一个代理类

示例

需求：

使用mybatis实现对数据的逻辑删除。

如果执行删除操作，则将表中status字段修改成1
查询和修改时，需要将status=0作为where条件

对于新增和修改，如果有username和phone字段，则需要动态添加字段username_enc和phone_enc为对应字段的密文，并保存到数据库

根据上述需求，需要在mybatis拦截器中解析sql，并动态重写sql。

maven 依赖

<?xml version="1.0"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><!--<version>2.2.5.RELEASE</version>--><version>1.5.5.RELEASE</version><relativePath/></parent><groupId>com.example</groupId><artifactId>test-shardingsphere</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><description>Demo project for Spring Boot</description><dependencies><!--swagger ui--><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger2</artifactId><version>2.9.2</version></dependency><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger-ui</artifactId><version>2.9.2</version></dependency><!--springboot--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-configuration-processor</artifactId></dependency><!--mybatis starter--><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>1.3.2</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.41</version></dependency><!--lombok--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.16.10</version></dependency><dependency><groupId>org.aspectj</groupId><artifactId>aspectjrt</artifactId><version>1.8.13</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-aop</artifactId></dependency><!--sql解析--><dependency><groupId>com.github.jsqlparser</groupId><artifactId>jsqlparser</artifactId><version>3.1</version></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><executions><execution><goals><goal>repackage</goal></goals></execution></executions></plugin><plugin><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-maven-plugin</artifactId><version>1.3.2</version><configuration> <!--配置文件的位置--><configurationFile>src/main/resources/generatorConfig.xml</configurationFile><verbose>true</verbose><overwrite>true</overwrite></configuration><executions><execution><id>Generate MyBatis Artifacts</id><goals><goal>generate</goal></goals></execution></executions><dependencies><dependency><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-core</artifactId><version>1.3.2</version></dependency></dependencies></plugin></plugins></build>
</project>

mybatis拦截器配置

@Configuration
public class MyBatisConfig {@Autowiredprivate SqlSessionFactory sqlSessionFactory;@PostConstructpublic void addMySqlInterceptor() {MyBatisInterceptor interceptor = new MyBatisInterceptor();sqlSessionFactory.getConfiguration().addInterceptor(interceptor);}
}

自定义拦截器

/**
*
*/
@Intercepts({@Signature(type = Executor.class, method = "update", args = { MappedStatement.class, Object.class }),@Signature(type = Executor.class, method = "query", args={MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})
})
@Slf4j
public class MyBatisInterceptor implements Interceptor{@Overridepublic Object intercept(Invocation invocation) throws Throwable {// 拦截sqlObject[] args = invocation.getArgs();MappedStatement statement = (MappedStatement) args[0];Object parameterObject = args[1];BoundSql boundSql = statement.getBoundSql(parameterObject);String sql = boundSql.getSql();if (sql==null||"".equals(sql)) {return invocation.proceed();}// 重写sqlresetSql2Invocation(invocation,sql);return invocation.proceed();}private void resetSql2Invocation(Invocation invocation,String sql) throws SQLException {final Object[] args = invocation.getArgs();MappedStatement statement = (MappedStatement) args[0];MapperMethod.ParamMap parameterObject = (MapperMethod.ParamMap)args[1];final BoundSql boundSql = statement.getBoundSql(parameterObject);List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();//根据不同的sql类型重新构建新的sql语句String newsql = "";MyOperationType myOperationType = null;switch (statement.getSqlCommandType()) {case INSERT:myOperationType = new MyInsertOperationType();newsql = myOperationType.handle(statement,parameterMappings, parameterObject, sql);break;case UPDATE:myOperationType = new MyUpdateOperationType();newsql = myOperationType.handle(statement,parameterMappings, parameterObject, sql);break;case DELETE:myOperationType = new MyDeleteOperationType();newsql = myOperationType.handle(statement,parameterMappings, parameterObject, sql);break;case SELECT:myOperationType = new MySelectOperationType();newsql = myOperationType.handle(statement,parameterMappings, parameterObject, sql);break;default:break;}// 重新new一个查询语句对像BoundSql newBoundSql = new BoundSql(statement.getConfiguration(), newsql, parameterMappings,parameterObject);// 把新的查询放到statement里MappedStatement newStatement = copyFromMappedStatement(statement, new BoundSqlSqlSource(newBoundSql));// 重新设置新的参数args[0] = newStatement;System.out.println("sql语句："+newsql);}//构造新的statementprivate MappedStatement copyFromMappedStatement(MappedStatement ms, SqlSource newSqlSource) {MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(), newSqlSource,ms.getSqlCommandType());builder.resource(ms.getResource());builder.fetchSize(ms.getFetchSize());builder.statementType(ms.getStatementType());builder.keyGenerator(ms.getKeyGenerator());if (ms.getKeyProperties() != null && ms.getKeyProperties().length != 0) {StringBuilder keyProperties = new StringBuilder();for (String keyProperty : ms.getKeyProperties()) {keyProperties.append(keyProperty).append(",");}keyProperties.delete(keyProperties.length() - 1, keyProperties.length());builder.keyProperty(keyProperties.toString());}builder.timeout(ms.getTimeout());builder.parameterMap(ms.getParameterMap());builder.resultMaps(ms.getResultMaps());builder.resultSetType(ms.getResultSetType());builder.cache(ms.getCache());builder.flushCacheRequired(ms.isFlushCacheRequired());builder.useCache(ms.isUseCache());return builder.build();}@Overridepublic Object plugin(Object target) {return Plugin.wrap(target, this);}@Overridepublic void setProperties(Properties properties) {// TODO Auto-generated method stub}class BoundSqlSqlSource implements SqlSource {private BoundSql boundSql;public BoundSqlSqlSource(BoundSql boundSql) {this.boundSql = boundSql;}@Overridepublic BoundSql getBoundSql(Object parameterObject) {return boundSql;}}}

使用jsqlparser重写sql

jsqlparser基本api操作参考：https://blog.csdn.net/qq_35986709/article/details/109806402

public interface MyOperationType {String handle(MappedStatement statement,List<ParameterMapping> parameterMappings, MapperMethod.ParamMap parameterObject, String sql);default boolean isNotIn(ParameterMapping parameterMapping,List<ParameterMapping> parameterMappings){if(parameterMappings!=null){for(ParameterMapping it:parameterMappings){if(it.getProperty().equals(parameterMapping.getProperty())){return false;}}}return true;}default List<String> encList(String tableName,List<Column> columns){List<String> result = new ArrayList<>();List<String> list = getEncMap().get(tableName);if(list!=null&&columns!=null){for(Column col:columns){if(list.contains(col.getColumnName())){result.add(col.getColumnName());}}}return result;}default String getColumnValue(MapperMethod.ParamMap parameterObject,List<ParameterMapping> parameterMappings,List<Column> columns,String column){if(columns!=null){for(int i=0;i<columns.size();i++){Column col = columns.get(i);if(column.equals(col.getColumnName())){ParameterMapping parameterMapping = parameterMappings.get(i);String property = parameterMapping.getProperty();Object result = parameterObject.get(property);return (String)result;}}}return null;}Map<String,List<String>> getEncMap();
}public abstract class MyDefaultOperationType implements MyOperationType{Map<String,List<String>> encMaps = new HashMap<>();/*** 假设只对t_user表的username和phone2个字段进行加密存储*/public MyDefaultOperationType(){encMaps.put("t_user", Arrays.asList("username","phone"));}@Overridepublic Map<String, List<String>> getEncMap() {return encMaps;}
}public class MyInsertOperationType extends MyDefaultOperationType{@Overridepublic String handle(MappedStatement mystatement,List<ParameterMapping> parameterMappings, MapperMethod.ParamMap parameterObject, String sql) {try {//解析sql语句Statement statement = CCJSqlParserUtil.parse(sql);//强制转换成insert对象Insert insert = (Insert) statement;//从insert中获取表名Table table = insert.getTable();//从insert中获取字段名List<Column> columns = insert.getColumns();List<String> needEncs = encList(table.getName(), columns);if (!needEncs.isEmpty()) {ExpressionList list = (ExpressionList) insert.getItemsList();for(String col:needEncs) {String newCol = col+"_enc";Column miwen = new Column(newCol);//在insert里添加一个字段columns.add(miwen);//在insert的value里添加一个占位符？list.getExpressions().add(new JdbcParameter());//将新增的字段添加到mybatis框架的字段集合中ParameterMapping parameterMapping = new ParameterMapping.Builder(mystatement.getConfiguration(),newCol,String.class).build();if(isNotIn(parameterMapping,parameterMappings)) {parameterMappings.add(parameterMapping);}//添加参数值parameterObject.put(newCol, getColumnValue(parameterObject,parameterMappings,columns,col)+"123");}insert.setItemsList(list);}return insert.toString();}catch (Exception e){throw new RuntimeException("解析sql异常",e);}}
}public class MyUpdateOperationType extends MyDefaultOperationType {@Overridepublic String handle(MappedStatement mystatement,List<ParameterMapping> parameterMappings, MapperMethod.ParamMap parameterObject, String sql) {try {Statement statement = CCJSqlParserUtil.parse(sql);Update update = (Update)statement;Table table = update.getTable();List<Column> columns = update.getColumns();List<String> needEncs = encList(table.getName(), columns);if (!needEncs.isEmpty()) {List<Expression> expressions = update.getExpressions();for(String col:needEncs) {String newCol = col+"_enc";Column miwen = new Column(table,newCol);Expression expression = new JdbcParameter();expressions.add(expression);//添加参数keyParameterMapping parameterMapping = new ParameterMapping.Builder(mystatement.getConfiguration(),newCol,String.class).build();if(isNotIn(parameterMapping,parameterMappings)) {int index = parameterMappings.size()-(parameterMappings.size()- columns.size());parameterMappings.add(index,parameterMapping);}columns.add(miwen);//添加参数值parameterObject.put(newCol, getColumnValue(parameterObject,parameterMappings,columns,col)+"123");}Expression where = update.getWhere();EqualsTo status = new EqualsTo();status.setLeftExpression(new Column(table, "status"));StringValue stringValue = new StringValue("0");status.setRightExpression(stringValue);if(where!=null) {AndExpression lastwhere = new AndExpression(where, status);update.setWhere(lastwhere);}else{update.setWhere(status);}update.setExpressions(expressions);}return update.toString();}catch (Exception e){throw new RuntimeException("解析sql异常",e);}}
}public class MyDeleteOperationType extends MyDefaultOperationType {@Overridepublic String handle(MappedStatement mystatement,List<ParameterMapping> parameterMappings, MapperMethod.ParamMap parameterObject, String sql) {try {Statement statement = CCJSqlParserUtil.parse(sql);Delete delete = (Delete) statement;Table table = delete.getTable();Update update = new Update();update.setTable(table);update.setColumns(Arrays.asList(new Column(table,"status")));update.setExpressions(Arrays.asList(new StringValue("1")));update.setWhere(delete.getWhere());return update.toString();}catch (Exception e){throw new RuntimeException("解析sql异常",e);}}
}public class MySelectOperationType extends MyDefaultOperationType {@Overridepublic String handle(MappedStatement mystatement,List<ParameterMapping> parameterMappings, MapperMethod.ParamMap parameterObject, String sql) {try {Statement statement = CCJSqlParserUtil.parse(sql);Select select = (Select) statement;PlainSelect plain = (PlainSelect) select.getSelectBody();FromItem fromItem = plain.getFromItem();String tableName = fromItem.toString();Table table = new Table();table.setAlias(fromItem.getAlias());table.setName(tableName);Expression where = plain.getWhere();EqualsTo status = new EqualsTo();status.setLeftExpression(new Column(table, "status"));StringValue stringValue = new StringValue("0");status.setRightExpression(stringValue);if(where!=null) {AndExpression lastwhere = new AndExpression(where, status);plain.setWhere(lastwhere);}else{plain.setWhere(status);}return select.toString();}catch (Exception e){throw new RuntimeException("解析sql异常",e);}}
}

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