mybatis实现分页
Mybatis使用RowBounds对象进行分页,它是针对ResultSet结果集执行的内存分页,而非物理分页。如果想要实现物理分页,则可以在sql内直接书写带有物理分页的参数来完成,也可以使用分页插件来完成物理分页。
分页插件的基本原理是使用Mybatis提供的插件接口,实现自定义插件,在插件的拦截方法内拦截待执行的sql,然后重写sql,根据dialect方言,添加对应的物理分页语句和物理分页参数。
分页插件
mybatis分页主要是使用了mybatis中提供的拦截器功能,实现Interceptor接口,重写intercept方法
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@Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class,Integer.class})}) public class MyPageInterceptor implements Interceptor { private int page; private int size; @SuppressWarnings("unused") private String dbType; @SuppressWarnings("unchecked") @Override public Object intercept(Invocation invocation) throws Throwable { StatementHandler statementHandler = (StatementHandler)invocation.getTarget(); MetaObject metaObject = SystemMetaObject.forObject(statementHandler); while(metaObject.hasGetter("h")){ Object object = metaObject.getValue("h"); metaObject = SystemMetaObject.forObject(object); } while(metaObject.hasGetter("target")){ Object object = metaObject.getValue("target"); metaObject = SystemMetaObject.forObject(object); } MappedStatement mappedStatement = (MappedStatement)metaObject.getValue("delegate.mappedStatement"); String mapId = mappedStatement.getId(); if(mapId.matches(".+ByPager$")){ ParameterHandler parameterHandler = (ParameterHandler)metaObject.getValue("delegate.parameterHandler"); Map<String, Object> params = (Map<String, Object>)parameterHandler.getParameterObject(); page = (int)params.get("page"); size = (int)params.get("size"); String sql = (String) metaObject.getValue("delegate.boundSql.sql"); sql += " limit "+(page-1)*size +","+size; metaObject.setValue("delegate.boundSql.sql", sql); } return invocation.proceed(); } @Override public Object plugin(Object target) { return Plugin.wrap(target, this); } @Override public void setProperties(Properties properties) { String limit = properties.getProperty("limit","10"); this.page = Integer.parseInt(limit); this.dbType = properties.getProperty("dbType", "mysql"); } }
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