mybatis物理分页
拦截器的写法
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.List;
import java.util.Properties;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
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.SystemMetaObject;
import org.apache.ibatis.scripting.defaults.DefaultParameterHandler;
import org.apache.log4j.Logger;
/**
* @description mybatis分页拦截器，目前只实现了oracle和MySQL的
* @author wangming
* @date 2016年2月15日 下午2:51:13
*/
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class}),
@Signature(type = ResultSetHandler.class, method = "handleResultSets", args = {Statement.class})})
@SuppressWarnings("rawtypes")
public class PageHelper implements Interceptor {
private static final Logger logger = Logger.getLogger(PageHelper.class);
//数据库类型，从配置文件中获取
private String databaseType;
public String getDatabaseType() {
return databaseType;
}
public void setDatabaseType(String databaseType) {
this.databaseType = databaseType;
}
private static final ThreadLocal<Page> localPage = new ThreadLocal<Page>();
/**
* 开始分页
* @param pageNum
* @param pageSize
*/
public static void startPage(int pageNum, int pageSize) {
localPage.set(new Page(pageNum, pageSize));
}
/**
* 结束分页并返回结果，该方法必须被调用，否则localPage会一直保存下去，直到下一次startPage
* @return
*/
public static Page endPage() {
Page page = localPage.get();
localPage.remove();
return page;
}
@SuppressWarnings("unchecked")
@Override
public Object intercept(Invocation invocation) throws Throwable {
if (localPage.get() == null) {
return invocation.proceed();
}
if (invocation.getTarget() instanceof StatementHandler) {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
MetaObject metaStatementHandler = SystemMetaObject.forObject(statementHandler);
// 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 = SystemMetaObject.forObject(object);
}
// 分离最后一个代理对象的目标类
while (metaStatementHandler.hasGetter("target")) {
Object object = metaStatementHandler.getValue("target");
metaStatementHandler = SystemMetaObject.forObject(object);
}
MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
//分页信息if (localPage.get() != null) {
Page page = localPage.get();
BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
// 分页参数作为参数对象parameterObject的一个属性
String sql = boundSql.getSql();
// 重写sql
String pageSql = buildPageSql(sql, page);
//重写分页sql
metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
Connection connection = (Connection) invocation.getArgs()[0];
// 重设分页参数里的总页数等
setPageParameter(sql, connection, mappedStatement, boundSql, page);
// 将执行权交给下一个拦截器
return invocation.proceed();
} else if (invocation.getTarget() instanceof ResultSetHandler) {
Object result = invocation.proceed();
Page page = localPage.get();
page.setResult((List) result);
return result;
}
return null;
}
/**
* 只拦截这两种类型的
* <br>StatementHandler
* <br>ResultSetHandler
* @param target
* @return
*/
@Override
public Object plugin(Object target) {
if (target instanceof StatementHandler || target instanceof ResultSetHandler) {
return Plugin.wrap(target, this);
} else {
return target;
}
}
@Override
public void setProperties(Properties properties) {
}
/**
* 修改原SQL为分页SQL
* @param sql 原始sql
* @param page 分页信息
* @return
*/
private String buildPageSql(String sql, Page page) {
StringBuilder pageSql = new StringBuilder(200);
pageSql.append(sql);
if ("mysql".equalsIgnoreCase(databaseType)) {
return getMysqlPageSql(page, pageSql);
} else if ("oracle".equalsIgnoreCase(databaseType)) {
return getOraclePageSql(page, pageSql);
}
return pageSql.toString();
}
/**
* 获取Mysql数据库的分页查询语句
* @param page 分页对象
* @param pageSql 包含原sql语句的StringBuffer对象
* @return Mysql数据库分页语句
*/
private String getMysqlPageSql(Page page, StringBuilder pageSql) {
// 计算第一条记录的位置，Mysql分页是通过limit进行的，而Mysql的行是从0开始的
pageSql.append(" limit ").append(page.getStartRow()).append(" , ").append(page.getPageSize());
return pageSql.toString();
}
/**
* 获取Oracle数据库的分页查询语句
* @param page 分页对象
* @param pageSql 包含原sql语句的StringBuffer对象
* @return Oracle数据库的分页查询语句
*/
private String getOraclePageSql(Page page, StringBuilder pageSql) {
// 计算第一条记录的位置，Oracle分页是通过rownum进行的，而rownum是从1开始的
final int offset = (page.pageNum - 1) * page.getPageSize() + 1;
pageSql.insert(0, " select u.*, rownum r from ( ").append(") u where rownum < ")
.append(offset + page.getPageSize());
pageSql.insert(0, "select * from ( ").append(" ) where r >= ").append(offset);
return pageSql.toString();
}
/**
* 获取总记录数
* @param sql
* @param connection
* @param mappedStatement
* @param boundSql
* @param page
*/
private void setPageParameter(String sql, Connection connection, MappedStatement mappedStatement,
BoundSql boundSql, Page page) {
// 记录总记录数
String countSql = "select count(0) from (" + sql + ")";
PreparedStatement countStmt = null;
ResultSet rs = null;
try {
countStmt = connection.prepareStatement(countSql);
BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql,
boundSql.getParameterMappings(), boundSql.getParameterObject());
setParameters(countStmt, mappedStatement, countBS, boundSql.getParameterObject());
rs = countStmt.executeQuery();
int totalCount = 0;
if (rs.next()) {
totalCount = rs.getInt(1);
}
page.setTotal(totalCount);
int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0) ? 0 : 1);
page.setPages(totalPage);
} catch (SQLException e) {
logger.error("Ignore this exception", e);
} finally {
try {
rs.close();
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
try {
countStmt.close();
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
}
}
/**
* 代入参数值
* @param ps
* @param mappedStatement
* @param boundSql
* @param parameterObject
* @throws SQLException
*/
private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql,
Object parameterObject) throws SQLException {
ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
parameterHandler.setParameters(ps);
}
/**
* @description 分页信息
* @author wangming
* @date 2016年2月15日 下午2:54:52
*/
public static class Page<E> {
private int pageNum;//当前页码
private int pageSize;//页大小
private int startRow;//起始行，插件会自动计算
private int endRow;//结束行，插件会自动计算
private long total;//总记录数，插件会自动计算
private int pages;//总页数，插件会自动计算
private List<E> result;//数据
public Page(int pageNum, int pageSize) {
this.pageNum = pageNum;
this.pageSize = pageSize;
this.startRow = pageNum > 0 ? (pageNum - 1) * pageSize : 0;
this.endRow = pageNum * pageSize;
}
public List<E> getResult() {
return result;
}
public void setResult(List<E> result) {
this.result = result;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public int getEndRow() {
return endRow;
}
public void setEndRow(int endRow) {
this.endRow = endRow;
}
public int getPageNum() {
return pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getStartRow() {
return startRow;
}
public void setStartRow(int startRow) {
this.startRow = startRow;
}
public long getTotal() {
return total;
}
public void setTotal(long total) {
this.total = total;
}
@Override
public String toString() {
return "Page{" +
"pageNum=" + pageNum +
", pageSize=" + pageSize +
", startRow=" + startRow +
", endRow=" + endRow +
", total=" + total +
", pages=" + pages +
'}';
}
}
}
配置文件
<!-- sqlSession工厂类 --> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="configLocation" value="classpath:mybatis-config.xml" /> <property name="dataSource" ref="dataSource" /> <!-- <property name="typeAliasesPackage" value="com.fairyland.jdp.**.domain,com.tzxm.invest.**.domain" /> --> <property name="mapperLocations"> <list> <value>classpath:com/fairyland/jdp/framework/**/*-Mapper.xml</value> <value>classpath:com/tzxm/**/mapper/*.xml</value> </list> </property> <property name="plugins"> <list> <bean class="com.tzxm.mybatis.PageHelper" > <property name="databaseType"> <value>oracle</value> </property> </bean> </list> </property> </bean>
service中调用
public PageHelper.Page<HashMap<String, Object>> selectByExample(RiskDef vo, com.tzxm.mybatis.PageHelper.Page page) {
PageHelper.startPage(page.getPageNum(), page.getPageSize());
_RiskDefMapper.selectByExample(vo);
return PageHelper.endPage();
}
调用service
PageHelper.Page<HashMap<String, Object>> page=riskdefservice.selectByExample(vo,new PageHelper.Page(1,10));
此page中就含有了分页所需要的各种信息。