刚开始项目，需要用到mybatis分页，网上看了很多插件，其实实现原理基本都大同小异，但是大部分都只给了代码，注释不全，所以参考了很多篇文章（每篇文章偷一点代码，评出来自己的，半抄袭），才自己模仿着写出了一个适合自己项目的分页插件，话不多说，直接上代码，相比大部分文章，注释算很完整了
最重要的拦截器
package com.dnkx.interceptor;
import java.sql.*;
import java.util.HashMap;
import java.util.Properties;
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 com.dnkx.pojo.Page;
@Intercepts({
@Signature(type=StatementHandler.class,method="prepare",args={Connection.class}),
@Signature(type = ResultSetHandler.class, method = "handleResultSets", args = {Statement.class})
})
public class PageInterceptor implements Interceptor{
//拦截分页关键字
private static final String SELECt_ID="page";
//插件运行的代码，它将代替原有的方法,要重写最重要的intercept了
@Override
public Object intercept(Invocation invocation) throws Throwable {
if (invocation.getTarget() instanceof StatementHandler) {
//这里我们有一个设定 如果查询方法含有Page 就进行分页 其他方法无视
//所以就要获取方法名
StatementHandler statementHandler=(StatementHandler)invocation.getTarget();
metaObject metaObject=SystemmetaObject.forObject(statementHandler);
MappedStatement mappedStatement=(MappedStatement)metaObject.getValue("delegate.mappedStatement");
String selectId=mappedStatement.getId();
String methorName=selectId.substring(selectId.lastIndexOf(".")+1).toLowerCase();
//然后判断下 如果含有Page 就获取sql
if(methorName.contains(SELECT_ID)){
BoundSql boundSql=(BoundSql)metaObject.getValue("delegate.boundSql");
//分页参数作为参数对象parameterObject的一个属性
String sql=boundSql.getSql();
System.out.println("获取到的sql:"+sql);
HashMap map=(HashMap)(boundSql.getParameterObject());
//Page page=(Page)(boundSql.getParameterObject());
Page page=(Page)map.get("page");
// 重写sql
String countSql=concatCountSql(sql);
String pageSql=concatPageSql(sql,page);
// System.out.println("重写的 count sql :"+countSql);
System.out.println("重写的 select sql :"+pageSql);
Connection connection = (Connection) invocation.getArgs()[0];
PreparedStatement countStmt = null;
ResultSet rs = null;
int totalCount = 0;
try {
countStmt = connection.prepareStatement(countSql);
rs = countStmt.executeQuery();
if (rs.next()) {
totalCount = rs.getInt(1);
}
} catch (SQLException e) {
System.out.println("Ignore this exception"+e);
} finally {
try {
rs.close();
countStmt.close();
} catch (SQLException e) {
System.out.println("Ignore this exception"+ e);
}
}
metaObject.setValue("delegate.boundSql.sql", pageSql);
//绑定count
page.setNumCount(totalCount);
}
}
return invocation.proceed();
}
// 拦截类型StatementHandler,重写plugin方法
@Override
public Object plugin(Object target) {
if (target instanceof StatementHandler) {
return Plugin.wrap(target, this);
}else {
return target;
}
}
@Override
public void setProperties(Properties properties) {
}
//改造sql
public String concatCountSql(String sql){
//StringBuffer sb=new StringBuffer("select count(*) from ");
StringBuffer sb=new StringBuffer();
sql=sql.toLowerCase();
if(sql.lastIndexOf("order")>0){
sql=sql.substring(0,sql.indexOf("order"));
}
sb.append("select count(*) from ("+sql+") tmp");
return sb.toString();
}
public String concatPageSql(String sql,Page page){
StringBuffer sb=new StringBuffer();
sb.append(sql);
sb.append(" limit ").append(page.getPageBegin()).append(" , ").append(page.getPageSize());
return sb.toString();
}
}
分页对象Page类
[java] view plain copy
package com.dnkx.pojo;
import java.util.HashMap;
import java.util.Map;
public class Page {
//----------分页-----------
private int pageSize;//每页显示条数
private int pageCurrentPage;//第几页
private int pageBegin;//开始位置
private int numCount;//总条数
private int pageTotal;//总条数
private String orderField = "";//控制排序页面显示的
private String orderDirection = "";
public Page(){
}
public Page(int pageSize, int pageCurrentPage) {
super();
this.pageSize = pageSize;
this.pageCurrentPage = pageCurrentPage;
}
public Page(Map map){
if(map.get("pageNum")!=null){
this.setPageCurrentPage(this.pageCurrentPage = Integer.parseInt(map.get("pageNum")));//要查询的页数
}else{
this.setPageCurrentPage(1);//设置初始值
}
if(map.get("numPerPage")!=null){
this.setPageSize(Integer.parseInt(map.get("numPerPage")));//每页显示条数
}else{
this.setPageSize(5);//设置初始值
}
if(map.get("orderField")!=null){
this.setOrderField(map.get("orderField"));
}
if(map.get("orderDirection")!=null){
this.setOrderDirection(map.get("orderDirection"));
}
}
public int getPageCurrentPage() {
return pageCurrentPage;
}
public void setPageCurrentPage(int pageCurrentPage) {
this.pageCurrentPage = pageCurrentPage;
}
public int getNumCount() {
return numCount;
}
public void setNumCount(int numCount) {
this.numCount = numCount;
}
public int getPageTotal() {
return (numCount%pageSize>0)?(numCount/pageSize+1):(numCount/pageSize);
}
public void setPageTotal(int pageTotal) {
this.pageTotal = pageTotal;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getPageBegin() {
return pageSize*(pageCurrentPage-1);
}
public void setPageBegin(int pageBegin) {
this.pageBegin = pageBegin;
}
public String getOrderField() {
return orderField;
}
public void setOrderField(String orderField) {
this.orderField = orderField;
}
public String getOrderDirection() {
return orderDirection;
}
public void setOrderDirection(String orderDirection) {
this.orderDirection = orderDirection;
}
public static Page getPage(int pageSize, int pageCurrentPage){
return new Page(pageSize,pageCurrentPage);
}
public static Page getPage(Map map){
return new Page(map);
}
}
Controller里面调用方式
public String list(HttpServletRequest request) {
long a=System.currentTimeMillis();
HashMap map=GetRequestMap.getMap(request);//自己封装的方法，取request的参数
Page page= Page.getPage(map);//初始化page
map.put("page", page);//把page对象放入参数集合(这个map是mybatis要用到的，包含查询条件，排序，分页等)
//控制排序页面显示的
map.put(map.get("orderField")+"", map.get("orderDirection"));
List list=employeeService.getListPage(map);
request.setAttribute("emlist", list);
request.setAttribute("page", page);
request.setAttribute("map", map);
//取page相关属性
page.getNumCount();//总条数
page.getPageTotal();//总页数
long b=System.currentTimeMillis();
System.out.println("---------耗时:"+(b-a)+"ms");
return "basic/employee_list";
}
最后，spring里面配置插件
好了，到此结束，本文仅供参考！也期待大神提意见
