mybatis分页插件
MyBatis allows you to intercept calls to at certain points within the execution of a mapped statement.By default, MyBatis allows plug-ins to intercept method calls of:
· Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)
· ParameterHandler (getParameterObject, setParameters)
· ResultSetHandler (handleResultSets, handleOutputParameters)
· StatementHandler (prepare, parameterize, batch, update, query)
1、mybatis-config.xml配置文件添加
<plugins>
<plugin interceptor="org.flex.examples.common.PaginationPlugin">
<property name="dialectClass" value="org.flex.examples.dialect.MySql5Dialect" />
</plugin>
</plugins>
2、分页拦截器编写
@Intercepts({ @Signature(type = RoutingStatementHandler.class, method = "prepare", args = { Connection.class }) })
public class PaginationPlugin implements Interceptor {
private static final Logger logger = LoggerFactory
.getLogger(PaginationPlugin.class);
/**
*
*/
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler stmtHandler = (StatementHandler) invocation
.getTarget();
BoundSql boundSql = stmtHandler.getBoundSql();
MetaObject metaObject = SystemMetaObject.forObject(
stmtHandler);
RowBounds rowBounds = (RowBounds) metaObject
.getValue("delegate.rowBounds");
if (rowBounds == null || rowBounds == RowBounds.DEFAULT) {
return invocation.proceed();
}
Dialect dialect = null;
//方言类
dialect = (Dialect) Class.forName(dialectClass).newInstance();
String originalSql = (String) metaObject
.getValue("delegate.boundSql.sql");
metaObject.setValue("delegate.boundSql.sql", dialect
.getLimitString(originalSql, rowBounds.getOffset(),
rowBounds.getLimit()));
metaObject.setValue("delegate.rowBounds.offset",
RowBounds.NO_ROW_OFFSET);
metaObject.setValue("delegate.rowBounds.limit",
RowBounds.NO_ROW_LIMIT);
System.out.println(boundSql.getSql());
if (logger.isDebugEnabled()) {
logger.info("生成分页SQL : " + boundSql.getSql());
}
return invocation.proceed();
}
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
public void setProperties(Properties properties) {
dialectClass=properties.getProperty("dialectClass");
}
private String dialectClass;
}
拦截RoutingStatementHandler类的prepare方法，通过反射获取RowBounds和sql
结合dialectClass，修改sql添加分页语句块，实现数据库分页。
dialectClass类是根据各个数据库的不同编写，举个例子MySQL分页是limit 1,20,
而Oracle分页是采用rownum来进行分页。
3、service层调用示例
public PageResult getUserPagination(User user,PageResult pageResult){
int offset=(pageResult.getPageNo()-1)*pageResult.getPageSize();
int limit=pageResult.getPageSize();
RowBounds rb=new RowBounds(offset,limit);
List<Map<String,Object>> dataList=userMapper.getUserPagination(user,rb);
int total=userMapper.getUserTotal(user);
pageResult.setDataList(dataList);
pageResult.setTotal(total);
return pageResult;
}
分页分成2个部分，一个是取得相应页号的记录集，另一个是取得总的一个记录数。
取得总记录数这个数据查询暂时是另外写的一个sql
总结：本文也参照了网上多个大神的版本，个人感觉这样实现是比较简单
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