ScrollableStatementHandlerInterceptor.java

package org.quickbundle.third.mybatis;

import java.sql.Connection;
import java.util.Properties;

import org.apache.ibatis.executor.statement.StatementHandler;
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;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.factory.DefaultObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.RowBounds;
import org.quickbundle.third.mybatis.dialect.DB2Dialect;
import org.quickbundle.third.mybatis.dialect.Dialect;
import org.quickbundle.third.mybatis.dialect.H2Dialect;
import org.quickbundle.third.mybatis.dialect.MySql5Dialect;
import org.quickbundle.third.mybatis.dialect.OracleDialect;
import org.quickbundle.third.mybatis.dialect.PostgreSQLDialect;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
public class ScrollableStatementHandlerInterceptor implements Interceptor {

	private final static Logger log = LoggerFactory.getLogger(ScrollableStatementHandlerInterceptor.class);

	public Object intercept(Invocation invocation) throws Throwable {
		StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
		BoundSql boundSql = statementHandler.getBoundSql();
		MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, new DefaultObjectFactory(), new DefaultObjectWrapperFactory());
		RowBounds rowBounds = (RowBounds) metaStatementHandler.getValue("delegate.rowBounds");
		if (rowBounds == null || rowBounds == RowBounds.DEFAULT || rowBounds.getOffset() < 0 || rowBounds.getLimit() < 0) {
			return invocation.proceed();
		}
		Configuration configuration = (Configuration) metaStatementHandler.getValue("delegate.configuration");
		Dialect.Type databaseType = null;
		try {
			databaseType = Dialect.Type.valueOf(configuration.getVariables().getProperty("dialect").toUpperCase());
		} catch (Exception e) {
			// ignore
		}
		if (databaseType == null) {
			throw new RuntimeException("the value of the dialect property in configuration.xml is not defined : "
					+ configuration.getVariables().getProperty("dialect"));
		}
		Dialect dialect = null;
		switch (databaseType) {
		//TODO 新的数据库支持
		case MYSQL:
			dialect = new MySql5Dialect();
			break;
		case POSTGRESQL:
			dialect = new PostgreSQLDialect();
			break;
		case H2:
			dialect = new H2Dialect();
			break;
		case ORACLE:
			dialect = new OracleDialect();
			break;
		case DB2:
			dialect = new DB2Dialect();
			break;
		}

		String originalSql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");
		metaStatementHandler.setValue("delegate.boundSql.sql", dialect.getLimitString(originalSql, rowBounds.getOffset(), rowBounds.getLimit()));
		metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
		metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
		if (log.isDebugEnabled()) {
			log.debug("Generating scrollable SQL : " + boundSql.getSql());
		}
		return invocation.proceed();
	}

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

	public void setProperties(Properties properties) {
	}
}