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5.2.0 更新日志
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‎wikis/en/Changelog.md

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## Changelog
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### 5.2.0 - 2020-07-26
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- Upgrading jsqlparser to version 3.2 makes sql parsing better and supports sqlserver better.
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- Modify the substitution regularity in sqlserver mode, and now allow spaces in `with( nolock)` brackets.
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- Solving the bugs in reasonable, pageSizeZero and offset usage, the meaning and result are more consistent now.
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- In the process of splicing paging SQL, a new line character is added to avoid invalid paging part caused by comments in the original SQL.
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- ROW_ID alias in Oracle and Db2 is changed to PAGEHELPER_ROW_ID to avoid conflict with common names.
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- Solve the special problem when using other interceptors with a single parameter ProviderSql (support mybatis 3.4.0+) [by Luo Zhenyu](https://github.com/luozhenyu)
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- Automatic identification of clickhouse is supported, and paging is performed by MySQL.
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- Change startRow, endRow type from int to long.
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- Page adds a `public <T> PageInfo<T> toPageInfo(Function<E, T> function)` method to convert the data in the query results.
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- Refer to `Oracle9iDialect` provided by pr#476, which is also a paging method used before. You can test and select the appropriate paging method by yourself.
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At present, there are two kinds of Oracle pagination as follows:
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```sql
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-- OracleDialect outer control range
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WHERE ROW_ID <= ? AND ROW_ID > ?
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-- Oracle9iDialect's internal and external control scope respectively
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TMP_PAGE WHERE ROWNUM <= ? ) WHERE ROW_ID > ?
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```
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- Adding `BoundSqlInterceptor` of PageHelper plug-in can process or simply read SQL in three stages, adding `boundSqlInterceptors`, and configuring multiple implementation class names that implement `BoundSqlInterceptor` interface, separated by English commas. PageHelper can also be set for this paging through a `PageHelper.startPage(x,x).boundSqlInterceptor(BoundSqlInterceptor boundSqlInterceptor)`.
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The biggest change of this update is the addition of `BoundSqlInterceptor`, which can intercept the SQL(BoundSQL object) of paging processing at runtime:
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```java
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/**
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* BoundSql 处理器
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*/
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public interface BoundSqlInterceptor {
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/**
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* boundsql 处理
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*
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* @param type 类型
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* @param boundSql 当前类型的 boundSql
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* @param cacheKey 缓存 key
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* @param chain 处理器链，通过 chain.doBoundSql 方法继续执行后续方法，也可以直接返回 boundSql 终止后续方法的执行
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* @return 允许修改 boundSql 并返回修改后的
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*/
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BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain);
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enum Type {
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/**
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* 原始SQL，分页插件执行前，先执行这个类型
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*/
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ORIGINAL,
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/**
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* count SQL，第二个执行这里
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*/
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COUNT_SQL,
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/**
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* 分页 SQL，最后执行这里
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*/
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PAGE_SQL
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}
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/**
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* 处理器链，可以控制是否继续执行
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*/
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interface Chain {
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Chain DO_NOTHING = new Chain() {
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@Override
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public BoundSql doBoundSql(Type type, BoundSql boundSql, CacheKey cacheKey) {
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return boundSql;
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}
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};
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BoundSql doBoundSql(Type type, BoundSql boundSql, CacheKey cacheKey);
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}
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}
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```
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The interface includes boundSql interface method, Type enumeration, and the definition of Chain interface, and you don't need to consider Chain when you implement it yourself.
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The interceptor is configured by `boundSqlInterceptors` parameter, and there are three situations when executing:
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1. Regardless of whether the currently executed SQL will be paged or not, interceptor methods of `Type.ORIGINAL` will be executed.
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2. When the paging method is called, the interceptor will continue to execute the interceptor method of `Type.COUNT_SQL`, which will only be executed when paging is executed and count query is specified.
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3. When paging method is called, if count > 0, interceptor method of `Type.PAGE_SQL` will be executed, which will only be executed when paging is executed.
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>With the specified parameter `PageHelper.startPage(1, Integer.MAX_VALUE, false).boundSqlInterceptor(BoundSqlInterceptor boundSqlInterceptor)`, it can also play the role of not paging and count query, but can execute interceptor method of `Type.ORIGINAL`.
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If you want to get the page before SQL execution, you only need to pay attention to `Type.ORIGINAL`, and the other two are before count execution and before page execution (when count=0, the page method will not be executed and will not be executed here).
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Take the test code as an example:
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```java
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public class TestBoundSqlInterceptor implements BoundSqlInterceptor {
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public static final String COMMENT = "\n /* TestBoundSqlInterceptor */\n";
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@Override
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public BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain) {
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if (type == Type.ORIGINAL) {
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String sql = boundSql.getSql();
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MetaObject metaObject = MetaObjectUtil.forObject(boundSql);
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metaObject.setValue("sql", sql + COMMENT);
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}
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return chain.doBoundSql(type, boundSql, cacheKey);
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}
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}
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```
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The above code modifies the original sql before SQL execution, but only adds a comment at the end, which does not affect SQL execution. It is configured in the following way:
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```xml
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<plugin interceptor="com.github.pagehelper.PageInterceptor">
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<!-- 支持通过Mapper接口参数来传递分页参数 -->
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<property name="helperDialect" value="mysql"/>
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<property name="boundSqlInterceptors"
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value="com.github.pagehelper.test.basic.provider.TestBoundSqlInterceptor,com.github.pagehelper.test.basic.provider.TestBoundSqlInterceptor"/>
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</plugin>
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```
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Here, in order to explain that the parameter value can be multiple, it is repeatedly configured once, that is, the above interceptor will execute it twice.
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With this configuration, the above SQL will modify the SQL when the page is executed.
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In addition to this configuration mode, temporary designation when PageHelper.startPage is also supported. This mode will put the interceptor at the chain head and execute it first, so you can control whether to execute it later or not, or you can do the final processing before returning after all subsequent executions.
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Example:
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```java
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PageHelper.startPage(1, 10).boundSqlInterceptor(new BoundSqlInterceptor() {
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@Override
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public BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain) {
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System.out.println("before: " + boundSql.getSql());
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BoundSql doBoundSql = chain.doBoundSql(type, boundSql, cacheKey);
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System.out.println("after: " + doBoundSql.getSql());
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if (type == Type.ORIGINAL) {
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Assert.assertTrue(doBoundSql.getSql().contains(TestBoundSqlInterceptor.COMMENT));
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}
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return doBoundSql;
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}
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});
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```
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### 5.1.11 - 2019-11-26
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- Added support for Shentong database **wangss**

‎wikis/zh/Changelog.md

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## 更新日志
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### 5.2.0 - 2020-07-26
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- jsqlparser升级到3.2版本，sql解析更好，对sqlserver支持更好。
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- 修改 sqlserver 方式中的替换正则，现在允许 with( nolock ) 括号中存在空格。
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- 解决 reasonable 和 pageSizeZero,以及 offset 用法中的bug，现在的含义和结果更一致。
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- 分页 SQL 拼接过程中增加换行符，避免原始 SQL 中存在注释导致分页部分无效。
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- Oracle 和 Db2 中的行号 ROW_ID 别名改为 PAGEHELPER_ROW_ID，避免和常用名称冲突。
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- 解决单个参数ProviderSql使用其他拦截器时的特殊问题（支持 mybatis 3.4.0+）[by 罗震宇](https://github.com/luozhenyu)
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- 支持自动识别 clickhouse，使用 MySQL 方式进行分页。
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- 将 startRow, endRow 类型从 int 改为 long。
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- Page 增加 `public <T> PageInfo<T> toPageInfo(Function<E, T> function)` 方法，用于转换查询结果中的数据。
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- 参考 pr#476 提供 `·`Oracle9iDialect`，这也是曾经用过的一种分页方式，可以自己测试选择合适的分页方式。
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目前提供的两种 Oracle 分页如下：
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```sql
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-- OracleDialect 外层控制范围
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WHERE ROW_ID <= ? AND ROW_ID > ?
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-- Oracle9iDialect 内外分别控制范围
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TMP_PAGE WHERE ROWNUM <= ? ) WHERE ROW_ID > ?
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```
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- 增加分页插件的 `BoundSqlInterceptor` 拦截器，可以在3个阶段对 SQL 进行处理或者简单读取，
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增加参数 `boundSqlInterceptors`，可以配置多个实现 `BoundSqlInterceptor` 接口的实现类名，
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使用英文逗号隔开。PageHelper调用时，也可以通过类似
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`PageHelper.startPage(x,x).boundSqlInterceptor(BoundSqlInterceptor boundSqlInterceptor)`针对本次分页进行设置。
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本次更新最大的变化是增加了 `BoundSqlInterceptor`，通过该接口可以在运行时拦截分页处理的 SQL（BoundSQL对象）：
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```java
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/**
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* BoundSql 处理器
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*/
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public interface BoundSqlInterceptor {
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/**
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* boundsql 处理
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*
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* @param type 类型
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* @param boundSql 当前类型的 boundSql
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* @param cacheKey 缓存 key
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* @param chain 处理器链，通过 chain.doBoundSql 方法继续执行后续方法，也可以直接返回 boundSql 终止后续方法的执行
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* @return 允许修改 boundSql 并返回修改后的
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*/
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BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain);
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enum Type {
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/**
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* 原始SQL，分页插件执行前，先执行这个类型
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*/
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ORIGINAL,
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/**
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* count SQL，第二个执行这里
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*/
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COUNT_SQL,
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/**
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* 分页 SQL，最后执行这里
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*/
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PAGE_SQL
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}
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/**
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* 处理器链，可以控制是否继续执行
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*/
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interface Chain {
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Chain DO_NOTHING = new Chain() {
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@Override
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public BoundSql doBoundSql(Type type, BoundSql boundSql, CacheKey cacheKey) {
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return boundSql;
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}
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};
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BoundSql doBoundSql(Type type, BoundSql boundSql, CacheKey cacheKey);
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}
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}
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```
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接口中包含了 boundSql 接口方法，还有 Type 枚举，和 Chain 接口的定义，自己实现的时候不需要考虑 Chain。
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通过 `boundSqlInterceptors` 参数配置拦截器，执行时存在下面三种情况：
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1. 不管当前执行的 SQL 是否会分页，都会执行 `Type.ORIGINAL` 类型的拦截器方法，配置后一定会执行。
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2. 调用分页方法时，拦截器会继续执行 `Type.COUNT_SQL` 类型的拦截器方法，这个方法只有执行分页并且指定要进行 count 查询时才会执行。
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3. 调用分页方法时，如果 count > 0，就会执行 `Type.PAGE_SQL` 类型的拦截器方法，这个方法只有执行分页时才会执行。
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>通过 `PageHelper.startPage(1, Integer.MAX_VALUE, false).boundSqlInterceptor(BoundSqlInterceptor boundSqlInterceptor)`
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>这种指定的参数时，也能起到不进行分页和count查询，但是可以执行 `Type.ORIGINAL` 类型的拦截器方法。
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当前拦截器在整个分页执行过程中，会执行3次，对应 Type 枚举的 3 个类型，执行顺序也一致。
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如果想获取分页 SQL 执行前的，只需要关注 Type.ORIGINAL，另外两种就是 count 执行前和分页执行前（count=0时分页方法不执行，这里也不会执行）。
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以测试代码为例：
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```java
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public class TestBoundSqlInterceptor implements BoundSqlInterceptor {
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public static final String COMMENT = "\n /* TestBoundSqlInterceptor */\n";
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@Override
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public BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain) {
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if (type == Type.ORIGINAL) {
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String sql = boundSql.getSql();
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MetaObject metaObject = MetaObjectUtil.forObject(boundSql);
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metaObject.setValue("sql", sql + COMMENT);
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}
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return chain.doBoundSql(type, boundSql, cacheKey);
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}
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}
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```
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上面这段代码在 sql 执行前先修改原始 SQL，只是在最后增加了一段注释，不影响 SQL 执行，通过下面的方式配置：
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```xml
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<plugin interceptor="com.github.pagehelper.PageInterceptor">
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<!-- 支持通过Mapper接口参数来传递分页参数 -->
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<property name="helperDialect" value="mysql"/>
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<property name="boundSqlInterceptors"
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value="com.github.pagehelper.test.basic.provider.TestBoundSqlInterceptor,com.github.pagehelper.test.basic.provider.TestBoundSqlInterceptor"/>
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</plugin>
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```
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这里为了说明该参数值可以是多个，因此重复配置了一次，也就是上面的拦截器会执行两次。
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这样配置后，上面的 SQL 在分页执行的时候就会修改 SQL。
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除了这种配置方式外，还支持 PageHelper.startPage 时临时指定，这种方式会把拦截器放到链头先执行，因此可以控制后续的是否执行，也可以在后续所有执行外，做最后处理再返回。
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示例：
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```java
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PageHelper.startPage(1, 10).boundSqlInterceptor(new BoundSqlInterceptor() {
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@Override
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public BoundSql boundSql(Type type, BoundSql boundSql, CacheKey cacheKey, Chain chain) {
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System.out.println("before: " + boundSql.getSql());
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BoundSql doBoundSql = chain.doBoundSql(type, boundSql, cacheKey);
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System.out.println("after: " + doBoundSql.getSql());
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if (type == Type.ORIGINAL) {
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Assert.assertTrue(doBoundSql.getSql().contains(TestBoundSqlInterceptor.COMMENT));
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}
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return doBoundSql;
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}
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});
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```
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### 5.1.11 - 2019-11-26
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- 增加神通数据库的支持 **wangss**

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