mybatis plugin编写

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尝试使用了一下mybati的插件功能

写了一个基础类备以后使用

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.mapping.MappedStatement;
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.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.RowBounds;

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

	private static final ObjectFactory OBJECT_FACTORY = new DefaultObjectFactory();
	private static final ObjectWrapperFactory OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
	
	private Properties properties;
	
	public abstract void preIntercept(MetaObject metaStatementHandler, Configuration configuration, MappedStatement mappedStatement, BoundSql boundSql, RowBounds rowBounds);
	
	@Override
	public final Object intercept(Invocation invocation) throws Throwable {
		
		StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
		MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, OBJECT_FACTORY, OBJECT_WRAPPER_FACTORY);
		
		// 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环可以分离出最原始的的目标类)
		while (metaStatementHandler.hasGetter("h")) {
			Object object = metaStatementHandler.getValue("h");
			metaStatementHandler = MetaObject.forObject(object, OBJECT_FACTORY, OBJECT_WRAPPER_FACTORY);
		}
		// 分离最后一个代理对象的目标类
		while (metaStatementHandler.hasGetter("target")) {
			Object object = metaStatementHandler.getValue("target");
			metaStatementHandler = MetaObject.forObject(object, OBJECT_FACTORY, OBJECT_WRAPPER_FACTORY);
		}
		
		Configuration configuration     = (Configuration) metaStatementHandler.getValue("delegate.configuration");
		MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
		BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
		RowBounds rowBounds = (RowBounds) metaStatementHandler.getValue("delegate.rowBounds");
		
		preIntercept(metaStatementHandler, configuration, mappedStatement, boundSql, rowBounds);
		
		return invocation.proceed();
	}

	@Override
	public final Object plugin(Object target) {
		if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
	}
	
	public Properties getProperties() {
		return properties;
	}

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

}