1. [代码]Mybatis全局配置文件
< plugin interceptor = "com.has.core.page.PaginationInterceptor" />
2. [文件] PaginationInterceptor.java
@Intercepts ({ @Signature (type = StatementHandler. class , method = "prepare" , args = { Connection. class }) })
public class PaginationInterceptor implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
BoundSql boundSql = statementHandler.getBoundSql();
MetaObject metaStatementHandler = MetaObject.forObject(statementHandler);
RowBounds rowBounds = (RowBounds) metaStatementHandler.getValue( "delegate.rowBounds" );
if (rowBounds == null || rowBounds == RowBounds.DEFAULT) {
return invocation.proceed();
}
Configuration configuration = (Configuration) metaStatementHandler.getValue( "delegate.configuration" );
Dialect.Type databaseType = null ;
try {
databaseType = Dialect.Type.valueOf(configuration.getVariables().getProperty( "dialect" ).toUpperCase());
} catch (Exception e) {
}
if (databaseType == null ) {
throw new RuntimeException( "the value of the dialect property in configuration.xml is not defined : "
+ configuration.getVariables().getProperty( "dialect" ));
}
Dialect dialect = null ;
switch (databaseType) {
case MYSQL:
dialect = new MySql5Dialect();
break ;
case ORACLE:
dialect = new OracleDialect();
break ;
}
String originalSql = (String) metaStatementHandler.getValue( "delegate.boundSql.sql" );
metaStatementHandler.setValue( "delegate.boundSql.sql" ,
dialect.getLimitString(originalSql, rowBounds.getOffset(), rowBounds.getLimit()));
metaStatementHandler.setValue( "delegate.rowBounds.offset" , RowBounds.NO_ROW_OFFSET);
metaStatementHandler.setValue( "delegate.rowBounds.limit" , RowBounds.NO_ROW_LIMIT);
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this );
}
@Override
public void setProperties(Properties properties) {
}
}
3. [文件] Dialect.java
/**
* 数据库方言定义
*
*/
public abstract class Dialect {
public static enum Type {
MYSQL, ORACLE
}
public abstract String getLimitString(String sql, int skipResults, int maxResults);
}
4. [文件] MySql5Dialect.java
/**
* mysql方言分页类
*/
public class MySql5Dialect extends Dialect {
protected static final String SQL_END_DELIMITER = ";" ;
public String getLimitString(String sql, boolean hasOffset) {
return MySql5PageHepler.getLimitString(sql, - 1 , - 1 );
}
public String getLimitString(String sql, int offset, int limit) {
return MySql5PageHepler.getLimitString(sql, offset, limit);
}
public boolean supportsLimit() {
return true ;
}
}
5. [文件] OracleDialect.java
package com.chyjr.has.core.page.dialect;
/**
* oracel方言分页
*
*/
public class OracleDialect extends Dialect {
public String getLimitString(String sql, int offset, int limit) {
// TODO 未实现
return "";
}
}
6. [文件] MySql5PageHepler.java
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* mysql分页工具类
*/
public class MySql5PageHepler {
/**
* 得到查询总数的sql
*/
public static String getCountString(String querySelect) {
querySelect = getLineSql(querySelect);
int orderIndex = getLastOrderInsertPoint(querySelect);
int formIndex = getAfterFormInsertPoint(querySelect);
String select = querySelect.substring( 0 , formIndex);
// 如果SELECT 中包含 DISTINCT 只能在外层包含COUNT
if (select.toLowerCase().indexOf( "select distinct" ) != - 1
|| querySelect.toLowerCase().indexOf( "group by" ) != - 1 ) {
return new StringBuffer(querySelect.length()).append( "select count(1) count from (" )
.append(querySelect.substring( 0 , orderIndex)).append( " ) t" ).toString();
} else {
return new StringBuffer(querySelect.length()).append( "select count(1) count " )
.append(querySelect.substring(formIndex, orderIndex)).toString();
}
}
/**
* 得到最后一个Order By的插入点位置
*
* @return 返回最后一个Order By插入点的位置
*/
private static int getLastOrderInsertPoint(String querySelect) {
int orderIndex = querySelect.toLowerCase().lastIndexOf( "order by" );
if (orderIndex == - 1 || !isBracketCanPartnership(querySelect.substring(orderIndex, querySelect.length()))) {
throw new RuntimeException( "My SQL 分页必须要有Order by 语句!" );
}
return orderIndex;
}
/**
* 得到分页的SQL
*
* @param offset
* 偏移量
* @param limit
* 位置
* @return 分页SQL
*/
public static String getLimitString(String querySelect, int offset, int limit) {
querySelect = getLineSql(querySelect);
// String sql = querySelect.replaceAll("[^\\s,]+\\.", "") + " limit " +
// offset + " ," + limit;
String sql = querySelect + " limit " + offset + " ," + limit;
return sql;
}
/**
* 将SQL语句变成一条语句，并且每个单词的间隔都是1个空格
*
* @param sql
* SQL语句
* @return 如果sql是NULL返回空，否则返回转化后的SQL
*/
private static String getLineSql(String sql) {
return sql.replaceAll( "[\r\n]" , " " ).replaceAll( "\\s{2,}" , " " );
}
/**
* 得到SQL第一个正确的FROM的的插入点
*/
private static int getAfterFormInsertPoint(String querySelect) {
String regex = "\\s+FROM\\s+" ;
Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(querySelect);
while (matcher.find()) {
int fromStartIndex = matcher.start( 0 );
String text = querySelect.substring( 0 , fromStartIndex);
if (isBracketCanPartnership(text)) {
return fromStartIndex;
}
}
return 0 ;
}
/**
* 判断括号"()"是否匹配,并不会判断排列顺序是否正确
*
* @param text
* 要判断的文本
* @return 如果匹配返回TRUE,否则返回FALSE
*/
private static boolean isBracketCanPartnership(String text) {
if (text == null || (getIndexOfCount(text, '(' ) != getIndexOfCount(text, ')' ))) {
return false ;
}
return true ;
}
/**
* 得到一个字符在另一个字符串中出现的次数
*
* @param text
* 文本
* @param ch
* 字符
*/
private static int getIndexOfCount(String text, char ch) {
int count = 0 ;
for ( int i = 0 ; i < text.length(); i++) {
count = (text.charAt(i) == ch) ? count + 1 : count;
}
return count;
}
}
2. [图片] Mybatis.jpg
