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‎README.md

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#### mybatis 分页插件
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基于 exectur 拦截 查询请求

‎pom.xml

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.zuicoding.platform</groupId>
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<artifactId>mybatis-pagination</artifactId>
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<version>0.0.1-SNAPSHOTS</version>
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<packaging>jar</packaging>
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<name>mybatis-pagination</name>
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<url>http://maven.apache.org</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<log.version>1.7.25</log.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.mybatis</groupId>
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<artifactId>mybatis</artifactId>
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<version>3.4.4</version>
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</dependency>
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<dependency>
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<groupId>org.slf4j</groupId>
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<artifactId>slf4j-api</artifactId>
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<version>${log.version}</version>
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</dependency>
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<dependency>
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<groupId>org.slf4j</groupId>
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<artifactId>slf4j-log4j12</artifactId>
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<version>${log.version}</version>
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</dependency>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.12</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎src/main/java/com/zuicoding/platform/App.java

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package com.zuicoding.platform;
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/**
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* Hello world!
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*
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*/
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public class App
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{
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public static void main( String[] args )
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{
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System.out.println( "Hello World!" );
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}
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}

‎src/main/java/com/zuicoding/platform/mybatis/dialect/IDialect.java

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package com.zuicoding.platform.mybatis.dialect;
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/**
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* Created by Stephen.liln on 2017/8/31.
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* <p>
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* Description :<p></p>
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*/
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public interface IDialect {
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String buildPaginationSql(String sql, int offset, int limit);
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String buildCountSql(String sql);
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/**
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* default implement
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*/
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public static enum DefaultDialect implements IDialect{
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MYSQL{
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@Override
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public String buildPaginationSql(String sql, int offset, int limit) {
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StringBuilder limitSql = new StringBuilder(sql);
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limitSql.append(" LIMIT ").append(offset).append(",").append(limit);
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return limitSql.toString();
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}
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@Override
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public String buildCountSql(String sql) {
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return String.format("SELECT COUNT(1) AS TOTAL FROM(%s) AS TEMP", sql);
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}
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},
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ORACLE {
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@Override
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public String buildPaginationSql(String sql, int offset, int limit) {
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return null;
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}
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@Override
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public String buildCountSql(String sql) {
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return null;
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}
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},
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SQLSERVER{
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@Override
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public String buildPaginationSql(String sql, int offset, int limit) {
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return null;
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}
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@Override
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public String buildCountSql(String sql) {
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return null;
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}
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};
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}
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}

‎src/main/java/com/zuicoding/platform/mybatis/pagination/Pager.java

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package com.zuicoding.platform.mybatis.pagination;
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/**
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* Created by Stephen.lin on 2017/8/4.
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* <p>
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* Description :<p></p>
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*/
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public class Pager {
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private int pageNum = 1;
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private int pageSize = 10;
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private int offset = 0;
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private int total = 0;
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private int pageTotal = 0;
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public Pager() {
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}
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public Pager(int pageNum, int pageSize) {
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this.pageNum = pageNum;
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this.pageSize = pageSize;
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}
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public Pager(int pageNum) {
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this.pageNum = pageNum;
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}
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public int getPageNum() {
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return pageNum;
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}
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public void setPageNum(int pageNum) {
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this.pageNum = pageNum;
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}
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public int getPageSize() {
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return pageSize;
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}
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public void setPageSize(int pageSize) {
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this.pageSize = pageSize;
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}
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public int getOffset() {
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offset = (pageNum - 1) * pageSize;
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return offset;
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}
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public int getTotal() {
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return total;
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}
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public void setTotal(int total) {
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this.total = total;
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}
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public int getPageTotal() {
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pageTotal = (pageTotal % pageSize ) == 0 ? pageTotal / pageSize : (pageTotal / pageSize) + 1;
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return pageTotal;
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}
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}

‎src/main/java/com/zuicoding/platform/mybatis/pagination/PaginationHandler.java

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package com.zuicoding.platform.mybatis.pagination;
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import com.zuicoding.platform.mybatis.dialect.IDialect;
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import org.apache.ibatis.builder.StaticSqlSource;
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import org.apache.ibatis.executor.Executor;
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import org.apache.ibatis.mapping.*;
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import org.apache.ibatis.plugin.*;
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import org.apache.ibatis.session.ResultHandler;
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import org.apache.ibatis.session.RowBounds;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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import java.util.Properties;
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/**
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* Created by Stephen.lin on 2017/8/31.
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* <p>
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* Description :<p>mybatis 分页插件</p>
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*/
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@Intercepts({
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@Signature(type = Executor.class,method = "query", args = { MappedStatement.class, Object.class,
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RowBounds.class, ResultHandler.class })
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})
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public class PaginationHandler implements Interceptor {
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private Logger log = LoggerFactory.getLogger(PaginationHandler.class);
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public static final ThreadLocal<Pager> localPage = new ThreadLocal<Pager>();
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private IDialect dialect = IDialect.DefaultDialect.MYSQL;
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private static final List<ResultMap> COUNT_RESULTMAPS = new ArrayList<>(1);
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private static final String COUNT_SQL_SUFFIX = "-SELECT-COUNT";
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/**
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* 以此方法名字结尾的查询
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*/
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private String methodSuffix = "ByPager";
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public static void pageStart(int pageNum,int pageSize){
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if (pageNum <=0) pageNum = 1;
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localPage.set(new Pager(pageNum,pageSize));
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}
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public static void pageStart(Pager pager){
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if (pager == null) pager = new Pager();
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localPage.set(pager);
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}
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public static void pageStart(){
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pageStart(null);
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}
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public static Pager pageEnd(){
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Pager pager = localPage.get();
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localPage.remove();
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return pager;
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}
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@Override
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public Object intercept(Invocation invocation) throws Throwable {
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MappedStatement ms = (MappedStatement) invocation.getArgs()[0];
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log.info("sql Command Type:{}",ms.getSqlCommandType());
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if (ms.getSqlCommandType() != SqlCommandType.SELECT) return invocation.proceed();
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if (log.isDebugEnabled()){
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log.debug("mappedStatement id : {}",ms.getId());
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}
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if (!ms.getId().endsWith(methodSuffix)) return invocation.proceed();
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Pager pager = localPage.get();
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if(pager == null){
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log.warn("page message is null");
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return invocation.proceed();
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}
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Object parameter = invocation.getArgs()[1];
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BoundSql originSql = ms.getBoundSql(parameter);
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if (log.isDebugEnabled()){
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log.debug("origin sql is:{}",originSql.getSql());
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}
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String countSql = this.dialect.buildCountSql(originSql.getSql());
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if (log.isDebugEnabled()){
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log.debug("count sql is : {}",countSql);
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}
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//有些查询不需要查询总数
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if (countSql != null && !"".equals(countSql.trim())){
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if (COUNT_RESULTMAPS.size() == 0){
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COUNT_RESULTMAPS.add(new ResultMap.Builder(ms.getConfiguration(),
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ms.getId()+COUNT_SQL_SUFFIX,Integer.class,
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Collections.<ResultMapping>emptyList()).build());
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}
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//构建 count bound sql
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BoundSql countBoundSql = new BoundSql(ms.getConfiguration(),
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countSql,originSql.getParameterMappings(),
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originSql.getParameterObject());
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Executor executor = (Executor) invocation.getTarget();
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//构建 count MappedStatement
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MappedStatement countMs = reBuildMappedStatement(ms,countBoundSql,true);
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List<Integer> list = executor.query(countMs,parameter,RowBounds.DEFAULT,null);
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if (list!=null && !list.isEmpty()){
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int total = list.get(0);
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pager.setTotal(total);
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}
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}
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String limitSql = this.dialect.buildPaginationSql(originSql.getSql(),pager.getOffset(),pager.getPageSize());
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if(log.isDebugEnabled()){
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log.debug("limit sql is : {}",limitSql);
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}
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BoundSql limitBoundSql = new BoundSql(ms.getConfiguration(),
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limitSql,originSql.getParameterMappings(),originSql.getParameterObject());
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MappedStatement newMs = reBuildMappedStatement(ms,limitBoundSql,false);
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invocation.getArgs()[0] = newMs;
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log.info(" reBuild limit sql finished...");
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return invocation.proceed();
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}
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/**
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* 构造新的MappedStatement 对象
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* @param ms
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* @param newBoundSql
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* @param isCount
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* @return
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*/
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private MappedStatement reBuildMappedStatement(MappedStatement ms,
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BoundSql newBoundSql,boolean isCount){
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String id = ms.getId();
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if (isCount){
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id += COUNT_SQL_SUFFIX;
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}
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if (log.isDebugEnabled()){
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log.debug("sql id is:{}",id);
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}
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MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(),
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id,
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new StaticSqlSource(ms.getConfiguration(),
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newBoundSql.getSql(),newBoundSql.getParameterMappings()), ms.getSqlCommandType());
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builder.resource(ms.getResource());
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builder.fetchSize(ms.getFetchSize());
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builder.statementType(ms.getStatementType());
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builder.keyGenerator(ms.getKeyGenerator());
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// if (ms.getKeyProperties() != null){
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// builder.keyProperty(StringUtils.join(ms.getKeyProperties(),","));
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// }
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builder.timeout(ms.getTimeout());
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builder.parameterMap(ms.getParameterMap());
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builder.resultSetType(ms.getResultSetType());
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builder.cache(ms.getCache());
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builder.flushCacheRequired(ms.isFlushCacheRequired());
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builder.useCache(ms.isUseCache());
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builder.resultMaps(ms.getResultMaps());
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//如果是构建 count mappedStatement,将 查询 count result map 设置进去
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if (isCount){
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builder.resultMaps(COUNT_RESULTMAPS);
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}
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return builder.build();
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}
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@Override
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public Object plugin(Object target) {
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if (target instanceof Executor){
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return Plugin.wrap(target,this);
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}
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return target;
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}
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@Override
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public void setProperties(Properties properties) {
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String dialectStr = properties.getProperty("dialect","mysql");
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if (log.isDebugEnabled()){
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log.debug("sql dialect is : {}",dialectStr);
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}
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try {
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IDialect.DefaultDialect defaultDialect = IDialect.DefaultDialect.valueOf(dialectStr);
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this.dialect = defaultDialect;
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}catch (Exception e){
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log.warn("No enum from default dialect:"+dialectStr);
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try {
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this.dialect = (IDialect)Class.forName(dialectStr).newInstance();
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}catch (Exception e1){
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throw new IllegalArgumentException(e1);
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}
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}
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this.methodSuffix = properties.getProperty("methodSuffix",this.methodSuffix);
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log.info(" init properties finished, dialect value is : {},methodSuffix",dialect,methodSuffix);
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}
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public IDialect getDialect() {
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return dialect;
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}
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public void setDialect(IDialect dialect) {
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this.dialect = dialect;
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}
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}

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