全栈笔记

import java.lang.reflect.Field;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import org.apache.ibatis.executor.resultset.ResultSetHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;

@Intercepts({ @Signature(method = "handleResultSets", type = ResultSetHandler.class, args = { Statement.class }) })
public class MapInterceptor implements Interceptor {

@SuppressWarnings("unused")
private Properties properties;

@Override
public Object intercept(Invocation invocation) throws Throwable {
ResultSetHandler resultSetHandler = (ResultSetHandler) invocation.getTarget();
Class clazz = resultSetHandler.getClass();
// 反射读取boundSql 获得sql语句
Field field = clazz.getDeclaredField("boundSql");
field.setAccessible(true);
BoundSql boundsql = (BoundSql) field.get(resultSetHandler);
String sql = boundsql.getSql();
// 如果sql中包含 MAP_KEY 和 MAP_VALUE 则被认为需要该将结果集转为Map类型
if (sql.contains("MAP_KEY") && sql.contains("MAP_VALUE")) {
try {
List> list = new ArrayList>();
Map map = new HashMap();
Statement statement = (Statement) invocation.getArgs()[0]; // 取得方法的参数Statement
ResultSet rs = statement.getResultSet(); // 取得结果集
while (rs.next()) {
String mapKey = rs.getString("MAP_KEY");
Object mapValue = rs.getObject("MAP_VALUE");
map.put(mapKey, mapValue); // 取得结果集后K、V关联后放到MAP当中
}
list.add(map);
// 这里返回list，而不是直接返回map
return list;
} catch (Exception e) {
// 如果出现异常，可能是冲突，则...
return invocation.proceed();
}

}
// 如果没有进行拦截处理，则执行默认逻辑
return invocation.proceed();
}

@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}

@Override
public void setProperties(Properties properties) {
this.properties = properties;
}

}