zoukankan      html  css  js  c++  java
  • MyBatis拦截器(插件)分页

    1、MyBatis核心配置文件:

    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration
    PUBLIC "-//ibatis.apache.org//DTD Config 3.0//EN"
    "http://ibatis.apache.org/dtd/ibatis-3-config.dtd">
    <configuration>
        <!-- 设置别名 -->
        <typeAliases>
            <!-- 2. 指定扫描包,会把包内所有的类都设置别名,别名的名称就是类名,大小写不敏感 -->
            <package name="com.sgl.entity" />
        </typeAliases>
        
        <plugins>
            <plugin interceptor="com.sgl.interceptor.PageInterceptor">
                <property name="limit" value="10"/>
                <property name="dbType" value="mysql"/>
            </plugin>
        </plugins>
    </configuration>

    PageInfo.java

    package com.sgl.interceptor;
    
    import java.util.List;
    
    import com.alibaba.fastjson.JSONObject;
    
    public class PageInfo {
        
        private int pageIndex;// 当前页
        private int pageSize = 10;// 每页记录数
        private int totalCount;// 总记录数
        private int pageCount;// 总页数
        private boolean hasPre;// 是否首页,true表示不是首页
        private boolean hasNext;// 是否尾页,true表示不是尾页
        private JSONObject filter;// 查询过滤条件
        private List<?> results;// 结果集
    
        public PageInfo() {
            super();
        }
    
        public PageInfo(int pageIndex, int pageSize) {
            super();
            this.pageIndex = pageIndex;
            this.pageSize = pageSize;
        }
    
        public int getPageIndex() {
            return pageIndex;
        }
    
        public void setPageIndex(int pageIndex) {
            this.pageIndex = pageIndex;
        }
    
        public int getPageSize() {
            return pageSize;
        }
    
        public void setPageSize(int pageSize) {
            this.pageSize = pageSize;
        }
    
        public int getTotalCount() {
            return totalCount;
        }
    
        public void setTotalCount(int totalCount) {
            this.totalCount = totalCount;
        }
    
        public int getPageCount() {
            return totalCount%pageSize==0?(totalCount/pageSize):(totalCount/pageSize+1);
        }
    
    
        public boolean getHasPre(){
            return (pageIndex>1);
        }
        
        public boolean getHasNext(){
            return (pageIndex<getPageCount());
        }
    
        public JSONObject getFilter() {
            return filter;
        }
    
        public void setFilter(JSONObject filter) {
            this.filter = filter;
        }
    
        public List<?> getResults() {
            return results;
        }
    
        public void setResults(List<?> results) {
            this.results = results;
        }
    
        @Override
        public String toString() {
            return "PageInfo [pageIndex=" + pageIndex + ", pageSize=" + pageSize + ", totalCount=" + totalCount
                    + ", pageCount=" + pageCount + ", hasPre=" + hasPre + ", hasNext=" + hasNext + ", filter=" + filter
                    + ", results=" + results + "]";
        }
    
    }

    2、简单例子:

    package com.sgl.interceptor;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.text.DateFormat;
    import java.util.Date;
    import java.util.List;
    import java.util.Locale;
    import java.util.Properties;
    
    import org.apache.ibatis.executor.parameter.ParameterHandler;
    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.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.session.Configuration;
    import org.apache.ibatis.type.TypeHandlerRegistry;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    @Intercepts({
            @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class, Integer.class }) })
    public class PageInterceptor implements Interceptor {
    
        private static Logger logger = LoggerFactory.getLogger(PageInterceptor.class);
    
        private static final String SELECT_ID = "selectpage";
    
        @Override
        public Object intercept(Invocation invocation) throws Throwable {
            StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
            Connection connection = (Connection) invocation.getArgs()[0];
            // 获取statementHandler包装类
            MetaObject statmentHandlerObject = SystemMetaObject.forObject(statementHandler);
            // 获取操作数据库接口映射的相关信息
            MappedStatement mappedStatement = (MappedStatement) statmentHandlerObject.getValue("delegate.mappedStatement");
            ParameterHandler parameterHandler = (ParameterHandler) statmentHandlerObject
                    .getValue("delegate.parameterHandler");
    
            String id = mappedStatement.getId();
            String sql = statementHandler.getBoundSql().getSql();// 获取执行的sql语句
            Object param = statementHandler.getBoundSql().getParameterObject();// 获取sql中的参数
    
            // 对id为selectPage的查询进行分页处理
            if (SELECT_ID.equals(id.substring(id.lastIndexOf(".") + 1).toLowerCase())) {
                // 获取分页参数
                PageInfo pageInfo = (PageInfo) parameterHandler.getParameterObject();
                int pageIndex = pageInfo.getPageIndex();
                int pageSize = pageInfo.getPageSize();
    
                // 获取查询总记录数
                int totalCount = getTotalCount(mappedStatement, statementHandler, connection);
                pageInfo.setTotalCount(totalCount);
                // 拼接分页查询sql语句
                String limitSql = sql.trim() + " limit " + (pageIndex - 1) * pageSize + " , " + pageSize;
    
                logger.info("执行的sql[方法]:=====》{}", id);
                logger.info("执行的sql[语句]:=====》{}", limitSql.replaceAll("[\s]+", " "));
                logger.info("执行的sql[参数]:=====》{}", param);
    
                // 将构建完成的分页sql语句赋值个体'delegate.boundSql.sql',替换原来的sql语句
                statmentHandlerObject.setValue("delegate.boundSql.sql", limitSql);
            } else {
                logger.info("执行的sql[方法]:=====》{}", id);
                logger.info("执行的sql[语句]:=====》{}", sql.replaceAll("[\s]+", " "));
                logger.info("执行的sql[参数]:=====》{}", param);
            }
    
            return invocation.proceed();
        }
    
        // 拦截类型StatementHandler
        @Override
        public Object plugin(Object object) {
            if (object instanceof StatementHandler) {
                return Plugin.wrap(object, this);
            } else {
                return object;
            }
        }
    
        @Override
        public void setProperties(Properties properties) {
    
        }
    
        // 获取查询的总记录数
        private int getTotalCount(MappedStatement mappedStatement, StatementHandler statementHandler,
                Connection connection) {
            StringBuffer sb = new StringBuffer();
            sb.append("SELECT COUNT(1) as count FROM (" + showSql(mappedStatement, statementHandler) + ") t ");
    
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
            int totalCount = 0;
            try {
                preparedStatement = connection.prepareStatement(sb.toString());
                resultSet = preparedStatement.executeQuery();
                if (resultSet.next()) {
                    totalCount = resultSet.getInt(1);
                }
            } catch (Exception e) {
                logger.info("分页查询获取总记录数发生异常====》{}", e.getMessage());
            } finally {
                try {
                    if (resultSet != null) {
                        resultSet.close();
                    }
                    if (preparedStatement != null) {
                        preparedStatement.close();
                    }
                } catch (Exception e2) {
                    logger.info("关闭资源异常====>{}" + e2.getMessage());
                }
            }
            return totalCount;
        }
    
        /**
         * 把sql语句中的?替换成实际参数值,并返回sql语句
         * 
         * @return
         */
        private String showSql(MappedStatement mappedStatement, StatementHandler statementHandler) {
            Configuration configuration = mappedStatement.getConfiguration();
            BoundSql boundSql = statementHandler.getBoundSql();
            String sql = boundSql.getSql().replaceAll("[\s]+", " ");
            List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
            Object parameterObject = boundSql.getParameterObject();
            if (parameterMappings.size() > 0 && parameterObject != null) {
                // 获取基础类型处理器注册器
                TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
                if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {// 判断参数类型是否已注册(判断是否是基本参数类型)
                    sql = sql.replaceFirst("\?", getParameterValue(parameterObject));
                } else {
                    MetaObject metaObject = configuration.newMetaObject(parameterObject);
                    for (ParameterMapping parameterMapping : parameterMappings) {
                        String propertyName = parameterMapping.getProperty();
                        if (metaObject.hasGetter(propertyName)) {
                            Object value = metaObject.getValue(propertyName);
                            sql = sql.replaceFirst("\?", getParameterValue(value));
                        } else if (boundSql.hasAdditionalParameter(propertyName)) {
                            Object additionalParameter = boundSql.getAdditionalParameter(propertyName);
                            sql = sql.replaceFirst("\?", getParameterValue(additionalParameter));
                        }
                    }
                }
            }
            return sql;
        }
    
        /**
         * 对参数值进行分类处理
         * 
         * @param object
         * @return
         */
        private String getParameterValue(Object object) {
            String value = null;
            if (object instanceof String) {
                value = "'" + object.toString() + "'";
            } else if (object instanceof Date) {
                DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT,
                        Locale.CHINA);
                value = "'" + dateFormat.format(new Date()) + "'";
            } else {
                if (object != null) {
                    value = object.toString();
                } else {
                    value = "";
                }
            }
            return value;
        }
    
    }

    3、原理解析:

    //注解拦截器并签名
    @Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class,Integer.class})})
    method="prepare"和StatementHandler服务类中prepare方法相对应。
    Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException;

      自定义的插件类,都需要使用@Intercepts注解,@Signature是对插件需要拦截的对象进行签名,type表示要拦截的类型,method表示拦截类中的方法,args是需要的参数,这里的参数在后面也可以获取到。

      StatementHandler:数据库会话器,专门用于处理数据库会话,statement的执行操作,是一个接口。

      MetaObject:mybatis工具类,可以有效的读取或修改一些重要对象的属性,基本思想是通过反射去获取和设置对象的属性值,只是MetaObject类不需要我们自己去实现具体反射的方法,已经封装好了。

      通过MetaObject.getValue()和MetaObject.setValue(name,value)方法去获取对象属性值和设置对象属性值。

    String sql = (String) metaObjectHandler.getValue("delegate.boundSql.sql");
    metaObjectHandler.setValue("delegate.boundSql.sql", limitSql);

    通过MetaObject属性的获取流程:

    MappedStatement mappedStatement = (MappedStatement) metaObjectHandler.getValue("delegate.mappedStatement");

      metaObjectHandler是一个MetaObject对象。

      首先通过metaStatementHandler.getValue(“delegate”)拿到真正实现StatementHandler接口的服务对象。

    public class RoutingStatementHandler implements StatementHandler {
    //delegate属性来自这里,是一个实现了StatementHandler接口的类
        private final StatementHandler delegate;
    //通过这里给delegate属性赋值
        public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
            switch(RoutingStatementHandler.SyntheticClass_1.$SwitchMap$org$apache$ibatis$mapping$StatementType[ms.getStatementType().ordinal()]) {
            case 1:
                this.delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            case 2:
                this.delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            case 3:
                this.delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            default:
                throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
            }
    
        }
    }

      拿到具体的服务对象(处理逻辑的StatementHandler实现类)后,再获取mappedStatement属性,我们再来看mappedStatement属性的定义:

    public abstract class BaseStatementHandler implements StatementHandler {
        protected final Configuration configuration;
        protected final ObjectFactory objectFactory;
        protected final TypeHandlerRegistry typeHandlerRegistry;
        protected final ResultSetHandler resultSetHandler;
        protected final ParameterHandler parameterHandler;
        protected final Executor executor;
        //定义在这里
        protected final MappedStatement mappedStatement;
        protected final RowBounds rowBounds;
        protected BoundSql boundSql;
    }

      可以看出是定义在BaseStatementHandler中的属性,三个具体的服务对象都会继承BaseStatementHandler。这里有很多和执行数据库操作相关的属性,如果我们需要的话,都可以通过上述方式获取,如果相获取下层对象的属性,按照这个写法一次获取也可以拿到。

      RoutingStatementHandler:不是真正的服务对象,它通过适配器模式找到正确的StatementHandler去执行操作。通过invocation.getTarget()获取到的是一个RoutingStatementHandler代理对象,再通过MappedStatement中不同的类型,找到具体的处理类。

      真正实现StatementHandler接口的服务对象有:SimpleStatementHandler,PreparedStatementHandler,CallableStatementHandler都继承BaseStatementHandler,它们分别对应是三种不同的执行器:SIMPLE:默认的简单执行器;REUSE:重用预处理语句的执行期;BATCH:重用语句和批量更新处理器。

      BoundSql: 用于组装SQL和参数,使用插件时需要通过它拿到当前运行的SQL和参数及参数规则。它有如下几个重要属性:

    public class BoundSql {
        private String sql;
        private List<ParameterMapping> parameterMappings;
        private Object parameterObject;
        private Map<String, Object> additionalParameters;
        private MetaObject metaParameters;
    }

      parameterObject:是参数本身,调用方法时传递进来的参数。可以是pojo,map或@param注解的参数等。

      parameterMappings:它是一个List,存储了许多ParameterMapping对象。这个对象会描述我们的参数,参数包括属性、名称、表达式、javaType、jdbcType等。

      sql:我们书写在mapper.xml文件中的一条sql语句。

      MappedStatement:存储mapper.xml文件中一条sql语句配置的所有信息。

      Connection:连接对象,在插件中会依赖它去进行一些数据库操作。

      Configuration:包含mybatis所有的配置信息。

      ParameterHandler:接口,对预编译语句进行参数设置。即将参数设置到sql语句中。它有两个重要方法:getParameterObject()用于获取参数对象和 
      setParameters(PreparedStatement var1)用于设置参数对象。

    在插件中我们使用了一个辅助类,来封装分页时会用到的一些参数,定义如下:

    /**
     * description:实现分页的辅助类,用于封装用于分页的一些参数
     */
    public class PageParam {
        private Integer defaultPage;
        //    默认每页显示条数
        private Integer defaultPageSize;
        //    是否启用分页功能
        private Boolean defaultUseFlag;
        //    是否检测当前页码的合法性(大于最大页码或小于最小页码都不合法)
        private Boolean defaultCheckFlag;
        //当前sql查询的总记录数,回填
        private Integer totle;
        //    当前sql查询实现分页后的总页数,回填
        private Integer totlePage;
    
        ...(省略get和set方法)

    当需要使用到分页功能时,我们只需要将分页参数封装到PageParam对象中,并且作为参数传递到查询方法中,插件中就会自动获取到这些参数,并且动态组分页的Sql查询语句。下面就是我们自定义的分页插件类实现:

    import org.apache.ibatis.executor.parameter.ParameterHandler;
    import org.apache.ibatis.executor.statement.RoutingStatementHandler;
    import org.apache.ibatis.executor.statement.StatementHandler;
    import org.apache.ibatis.mapping.BoundSql;
    import org.apache.ibatis.mapping.MappedStatement;
    import org.apache.ibatis.plugin.*;
    import org.apache.ibatis.reflection.MetaObject;
    import org.apache.ibatis.reflection.SystemMetaObject;
    import org.apache.ibatis.scripting.defaults.DefaultParameterHandler;
    import javax.security.auth.login.Configuration;
    import java.lang.reflect.InvocationTargetException;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.Map;
    import java.util.Properties;
    
    /**
     * description:插件分页
     */
    @Intercepts(@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class}))
    public class PageInterceptor implements Interceptor {
        //    默认页码
        private Integer defaultPage;
        //    默认每页显示条数
        private Integer defaultPageSize;
        //    是否启用分页功能
        private boolean defaultUseFlag;
        //    检测当前页码的合法性(大于最大页码或小于最小页码都不合法)
        private boolean defaultCheckFlag;
    
        @Override
        public Object intercept(Invocation invocation) throws Throwable {
            StatementHandler statementHandler = getActuralHandlerObject(invocation);
    
            MetaObject metaStatementHandler = SystemMetaObject.forObject(statementHandler);
    
            String sql = statementHandler.getBoundSql().getSql();
    
    //        检测未通过,不是select语句
            if (!checkIsSelectFalg(sql)) {
                return invocation.proceed();
            }
    
            BoundSql boundSql = statementHandler.getBoundSql();
    
            Object paramObject = boundSql.getParameterObject();
    
            PageParam pageParam = getPageParam(paramObject);
    
            if (pageParam == null)
                return invocation.proceed();
    
            Integer pageNum = pageParam.getDefaultPage() == null ? defaultPage : pageParam.getDefaultPage();
            Integer pageSize = pageParam.getDefaultPageSize() == null ? defaultPageSize : pageParam.getDefaultPageSize();
    
            Boolean useFlag = pageParam.isDefaultUseFlag() == null ? defaultUseFlag : pageParam.isDefaultUseFlag();
            Boolean checkFlag = pageParam.isDefaultCheckFlag() == null ? defaultCheckFlag : pageParam.isDefaultCheckFlag();
    
            //不使用分页功能
            if (!useFlag) {
                return invocation.proceed();
            }
    
            int totle = getTotle(invocation, metaStatementHandler, boundSql);
    
            //将动态获取到的分页参数回填到pageParam中
            setTotltToParam(pageParam, totle, pageSize);
    
            //检查当前页码的有效性
            checkPage(checkFlag, pageNum, pageParam.getTotlePage());
    
            //修改sql
            return updateSql2Limit(invocation, metaStatementHandler, boundSql, pageNum, pageSize);
        }
    
        @Override
        public Object plugin(Object o) {
            return Plugin.wrap(o, this);
        }
    
        //    在配置插件的时候配置默认参数
        @Override
        public void setProperties(Properties properties) {
            String strDefaultPage = properties.getProperty("default.page");
            String strDefaultPageSize = properties.getProperty("default.pageSize");
            String strDefaultUseFlag = properties.getProperty("default.useFlag");
            String strDefaultCheckFlag = properties.getProperty("default.checkFlag");
            defaultPage = Integer.valueOf(strDefaultPage);
            defaultPageSize = Integer.valueOf(strDefaultPageSize);
            defaultUseFlag = Boolean.valueOf(strDefaultUseFlag);
            defaultCheckFlag = Boolean.valueOf(strDefaultCheckFlag);
        }
    
    
        //    从代理对象中分离出真实statementHandler对象,非代理对象
        private StatementHandler getActuralHandlerObject(Invocation invocation) {
            StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
            MetaObject metaStatementHandler = SystemMetaObject.forObject(statementHandler);
            Object object = null;
    //        分离代理对象链,目标可能被多个拦截器拦截,分离出最原始的目标类
            while (metaStatementHandler.hasGetter("h")) {
                object = metaStatementHandler.getValue("h");
                metaStatementHandler = SystemMetaObject.forObject(object);
            }
    
            if (object == null) {
                return statementHandler;
            }
            return (StatementHandler) object;
        }
    
        //    判断是否是select语句,只有select语句,才会用到分页
        private boolean checkIsSelectFalg(String sql) {
            String trimSql = sql.trim();
            int index = trimSql.toLowerCase().indexOf("select");
            return index == 0;
        }
    
        /*
        获取分页的参数
    
        参数可以通过map,@param注解进行参数传递。或者请求pojo继承自PageParam  将PageParam中的分页数据放进去
         */
        private PageParam getPageParam(Object paramerObject) {
            if (paramerObject == null) {
                return null;
            }
    
            PageParam pageParam = null;
            //通过map和@param注解将PageParam参数传递进来,pojo继承自PageParam不推荐使用  这里从参数中提取出传递进来的pojo继承自PageParam
    
    //        首先处理传递进来的是map对象和通过注解方式传值的情况,从中提取出PageParam,循环获取map中的键值对,取出PageParam对象
            if (paramerObject instanceof Map) {
                Map<String, Object> params = (Map<String, Object>) paramerObject;
                for (Map.Entry<String, Object> entry : params.entrySet()) {
                    if (entry.getValue() instanceof PageParam) {
                        return (PageParam) entry.getValue();
                    }
                }
            } else if (paramerObject instanceof PageParam) {
    //            继承方式 pojo继承自PageParam 只取出我们希望得到的分页参数
                pageParam = (PageParam) paramerObject;
    
            }
            return pageParam;
        }
    
        //    获取当前sql查询的记录总数
        private int getTotle(Invocation invocation, MetaObject metaStatementHandler, BoundSql boundSql) {
    //        获取mapper文件中当前查询语句的配置信息
            MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
    
            //获取所有配置Configuration
            org.apache.ibatis.session.Configuration configuration = mappedStatement.getConfiguration();
    
    //        获取当前查询语句的sql
            String sql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");
    
    //        将sql改写成统计记录数的sql语句,这里是mysql的改写语句,将第一次查询结果作为第二次查询的表
            String countSql = "select count(*) as totle from (" + sql + ") $_paging";
    
    //        获取connection连接对象,用于执行countsql语句
            Connection conn = (Connection) invocation.getArgs()[0];
    
            PreparedStatement ps = null;
    
            int totle = 0;
    
            try {
    //            预编译统计总记录数的sql
                ps = conn.prepareStatement(countSql);
                //构建统计总记录数的BoundSql
                BoundSql countBoundSql = new BoundSql(configuration, countSql, boundSql.getParameterMappings(), boundSql.getParameterObject());
                //构建ParameterHandler,用于设置统计sql的参数
                ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, boundSql.getParameterObject(), countBoundSql);
                //设置总数sql的参数
                parameterHandler.setParameters(ps);
                //执行查询语句
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
    //                与countSql中设置的别名对应
                    totle = rs.getInt("totle");
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                if (ps != null)
                    try {
                        ps.close();
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }
            }
            return totle;
        }
    
        //    设置条数参数到pageparam对象
        private void setTotltToParam(PageParam param, int totle, int pageSize) {
            param.setTotle(totle);
            param.setTotlePage(totle % pageSize == 0 ? totle / pageSize : (totle / pageSize) + 1);
        }
    
        //    修改原始sql语句为分页sql语句
        private Object updateSql2Limit(Invocation invocation, MetaObject metaStatementHandler, BoundSql boundSql, int page, int pageSize) throws InvocationTargetException, IllegalAccessException, SQLException {
            String sql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");
            //构建新的分页sql语句
            String limitSql = "select * from (" + sql + ") $_paging_table limit ?,?";
            //修改当前要执行的sql语句
            metaStatementHandler.setValue("delegate.boundSql.sql", limitSql);
            //相当于调用prepare方法,预编译sql并且加入参数,但是少了分页的两个参数,它返回一个PreparedStatement对象
            PreparedStatement ps = (PreparedStatement) invocation.proceed();
            //获取sql总的参数总数
            int count = ps.getParameterMetaData().getParameterCount();
            //设置与分页相关的两个参数
            ps.setInt(count - 1, (page - 1) * pageSize);
            ps.setInt(count, pageSize);
            return ps;
        }
    
        //    验证当前页码的有效性
        private void checkPage(boolean checkFlag, Integer pageNumber, Integer pageTotle) throws Exception {
            if (checkFlag) {
                if (pageNumber > pageTotle) {
                    throw new Exception("查询失败,查询页码" + pageNumber + "大于总页数" + pageTotle);
                }
            }
        }
    }
  • 相关阅读:
    SpringBoot:第五篇 CommandLineRunner
    多列单个索引和联合索引的区别
    数据库从0到0.1 (一): LSM-Tree VS B-Tree
    SpringBoot:第四篇 集成Guava(本地缓存+分布式缓存)
    SpringBoot:第三篇 配置修改
    TSINGSEE青犀视频编译WebRTC Android版报错The only supported distros are xxxxxxx处理方式
    TSINGSEE青犀视频开发WebRTC视频推流播放平台前端获取视频流列表错误是什么原因?
    如何修改TSINGSEE青犀视频开发的多平台支持视频RTSPServer组件EasyRTSPServer-win的端口号?
    视频RTSPServer组件EasyRTSPServer-win测试视频无法拉取到流在VLC播放如何修复?
    TSINGSEE青犀视频开发EasyWasmPlayer H265播放器是如何实现视频截图功能的?
  • 原文地址:https://www.cnblogs.com/a591378955/p/8483554.html
Copyright © 2011-2022 走看看