【java框架ssm-mybatis】使用mybait自定义拦截器实现分页功能
作者：互联网
使用mybatis插件实现分页功能
前言：前几天在公司发现公司框架一个好用的分页功能，使用查询的实体类继承一个分页类，并且在前端传入分页信息。mybatis执行的时候就会自动进行分页操作。遂自己研究了下，是利用了mybatis的自定义插件功能。今天实现了下，实现代码如下，具体讲解待日后补加
首先是项目结构图，就是简单的ssm项目分层
其中分页的关键类是utils包下的MybatisPluginPage.java和BasePage
首先看下关键代码
BasePage.java
package com.tff622.idea.ssm.utils;
import java.util.List;
public class BasePage {
private int pageSize = 5;
private int pageNum = 1;//默认值
private int totalNum;
private int currentPage;
private int totalPage;
private List<?> list;
public BasePage(){
}
public BasePage(int pageNum) {
this.pageNum = pageNum;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public List<?> getList() {
return list;
}
public void setList(List<?> list) {
this.list = list;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getPageNum() {
return pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getTotalNum() {
return totalNum;
}
public void setTotalNum(int totalNum) {
this.totalNum = totalNum;
}
public int getTotalPage() {
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
}
MybatisPluginPage.java
package com.tff622.idea.ssm.utils;
import org.apache.commons.lang.StringUtils;
import org.apache.ibatis.executor.Executor;
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.mapping.ParameterMapping;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.springframework.stereotype.Component;
import java.lang.reflect.Method;
import java.util.Properties;
//@Intercepts({
// @Signature(
// type = ResultSetHandler.class,//这是指拦截哪个接口
// method = "query", //这个接口内的哪个方法名，不要拼错了
// args = {Statement.class})
//})
@Component
@Intercepts(@Signature(type = Executor.class, method = "query",
args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}))
public class MybatisPluginPage implements Interceptor {
public Object intercept(Invocation invocation) throws Throwable {
// Object target = invocation.getTarget(); //被代理对象
// Method method = invocation.getMethod(); //代理方法
Object[] args = invocation.getArgs(); //方法参数
// do something ...... 方法拦截前执行代码块
final MappedStatement mappedStatement = (MappedStatement) args[0];//获取执行的时的sql
Object resultType = args[1];//获取传参的对象
int pageSize;
int pageNum;
if (args[1] != null && args[1] instanceof BasePage) {//判断是否resultType是否为BasePage对象的子类 如果是则获取分页信息
BasePage pageMessage = (BasePage) resultType;
pageSize = pageMessage.getPageSize();
pageNum = pageMessage.getPageNum();
}else{// 否则不进行分页
return invocation.proceed();
}
//获取要执行的sql信息
BoundSql boundSql = mappedStatement.getBoundSql(resultType);
String sql = "select * from (" + boundSql.getSql() + ")a limit " + (pageNum - 1) * pageSize + "," + (pageNum) * pageSize;//重新组织sql
BoundSql newBoundsql = new BoundSql(mappedStatement.getConfiguration(), sql, boundSql.getParameterMappings(), resultType);//使用新的sql组建一个boundSql
MappedStatement newMs = newMapperStatement(mappedStatement, new BoundsqlRource(newBoundsql));//使用新的boundSql组建一个MappedStatement
for (ParameterMapping mapping : boundSql.getParameterMappings()) {
String prop = mapping.getProperty();
if (boundSql.hasAdditionalParameter(prop)) {
newBoundsql.setAdditionalParameter(prop, boundSql.getAdditionalParameter(prop));
}
}
invocation.getArgs()[0] = newMs;//将新的mappedStatement对象放入invocation中
Object result = invocation.proceed();
// do something .......方法拦截后执行代码块
return result;
}
private MappedStatement newMapperStatement(MappedStatement ms, SqlSource newsql) {
MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(), newsql, ms.getSqlCommandType());
builder.resource(ms.getResource());
builder.fetchSize(ms.getFetchSize());
builder.statementType(ms.getStatementType());
builder.keyGenerator(ms.getKeyGenerator());
if (ms.getKeyProperties() != null && ms.getKeyProperties().length > 0) {
builder.keyProperty(ms.getKeyProperties()[0]);
}
builder.timeout(ms.getTimeout());
builder.parameterMap(ms.getParameterMap());
builder.resultMaps(ms.getResultMaps());
builder.resultSetType(ms.getResultSetType());
builder.cache(ms.getCache());
builder.flushCacheRequired(ms.isFlushCacheRequired());
builder.useCache(ms.isUseCache());
return builder.build();
}
class BoundsqlRource implements SqlSource {
private BoundSql boundSql;
public BoundsqlRource(BoundSql boundSql) {
this.boundSql = boundSql;
}
@Override
public BoundSql getBoundSql(Object parameterObject) {
return boundSql;
}
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
@Override
public void setProperties(Properties properties) {
}
}
写好上面俩个类之后，开始调用，首先在mybatis-config中注册自定义插件
然后在vo类中继承BasePage
最后在调用查询列表接口时传入vo类就可以了
最后我们看一下效果，mapper文件中是这样写的
经过我们添加了分页功能后，执行的sql就变成了这样。
到此分页功能实现完毕。
参考文章：
https://www.jianshu.com/p/0a72bb1f6a21
https://blog.csdn.net/qq_29034189/article/details/113624023
标签：拦截器,mybait,自定义,int,builder,boundSql,ms,import,public 来源： https://blog.csdn.net/qq_38776903/article/details/113811158