Mybatis拦截器实现分页
作者：登顶
本文介绍使用Mybatis拦截器，实现分页；并且在dao层，直接返回自定义的分页对象。具有很好的参考价值，下面跟着小编一起来看下吧
最终dao层结果：
public interface ModelMapper {
Page<Model> pageByConditions(RowBounds rowBounds, Model record);
}
接下来一步一步来实现分页。
一.创建Page对象：
public class Page<T> extends PageList<T> {
private int pageNo = 1;// 页码，默认是第一页
private int pageSize = 15;// 每页显示的记录数，默认是15
private int totalRecord;// 总记录数
private int totalPage;// 总页数
public Page() {
}
public Page(int pageNo, int pageSize, int totalRecord,
List<T> results) {
this.pageNo = pageNo;
this.pageSize = pageSize;
this.totalRecord = totalRecord;
this.setResult(results);
int totalPage = totalRecord % pageSize == 0 ? totalRecord / pageSize : totalRecord / pageSize + 1;
this.setTotalPage(totalPage);
}
public int getPageNo() {
return pageNo;
}
public void setPageNo(int pageNo) {
this.pageNo = pageNo;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getTotalRecord() {
return totalRecord;
}
public void setTotalRecord(int totalRecord) {
this.totalRecord = totalRecord;
// 在设置总页数的时候计算出对应的总页数，在下面的三目运算中加法拥有更高的优先级，所以最后可以不加括号。
int totalPage = totalRecord % pageSize == 0 ? totalRecord / pageSize : totalRecord / pageSize + 1;
this.setTotalPage(totalPage);
}
public int getTotalPage() {
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("Page [pageNo=").append(pageNo).append(", pageSize=").append(pageSize).append(", results=")
.append(getResult()).append(", totalPage=").append(totalPage).append(", totalRecord=").append(totalRecord)
.append("]");
return builder.toString();
}
}
可以发现，这里继承了一个PageList类；这个类也是自己创建的一个类，实现List接口。为什么要PageList这个类，是因为Page需要实现List接口，而接口中的抽象方法，需要逐一实现，所以提供PageList在统一的地方写实现List接口的方法。
为什么Page需要实现List接口，这个会在稍后的代码中做解释。
PageList类：
public class PageList<T> implements List<T> {
private List<T> result;
public List<T> getResult() {
return result;
}
public void setResult(List<T> result) {
this.result = result;
}
@Override
public int size() {
return result.size();
}
@Override
public boolean isEmpty() {
return result.isEmpty();
}
@Override
public boolean contains(Object o) {
return result.contains(o);
}
@Override
public Iterator<T> iterator() {
return result.iterator();
}
@Override
public Object[] toArray() {
return result.toArray();
}
@Override
public <E> E[] toArray(E[] a) {
return result.toArray(a);
}
@Override
public boolean add(T e) {
return result.add(e);
}
@Override
public boolean remove(Object o) {
return result.remove(o);
}
@Override
public boolean containsAll(Collection<?> c) {
return result.containsAll(c);
}
@Override
public boolean addAll(Collection<? extends T> c) {
return result.addAll(c);
}
@Override
public boolean addAll(int index, Collection<? extends T> c) {
return result.addAll(index, c);
}
@Override
public boolean removeAll(Collection<?> c) {
return result.removeAll(c);
}
@Override
public boolean retainAll(Collection<?> c) {
return result.retainAll(c);
}
@Override
public void clear() {
result.clear();
}
@Override
public T get(int index) {
return result.get(index);
}
@Override
public T set(int index, T element) {
return result.set(index, element);
}
@Override
public void add(int index, T element) {
result.add(index, element);
}
@Override
public T remove(int index) {
return result.remove(index);
}
@Override
public int indexOf(Object o) {
return result.indexOf(o);
}
@Override
public int lastIndexOf(Object o) {
return result.lastIndexOf(o);
}
@Override
public ListIterator<T> listIterator() {
return result.listIterator();
}
@Override
public ListIterator<T> listIterator(int index) {
return result.listIterator(index);
}
@Override
public List<T> subList(int fromIndex, int toIndex) {
return result.subList(fromIndex, toIndex);
}
}
二.提供Dao以及mapper.xml
dao的写法：
Page<Model> pageByConditions(RowBounds rowBounds, Model record);
mapper.xml:
<!-- 表名 -->
<sql id="tableName" >
model
</sql>
<!-- 数据表所有列名 -->
<sql id="Base_Column_List" >
id,
name
</sql>
<!-- 查询字段 -->
<sql id="Base_Search_Param" >
<if test="id != null" >
and id = #{id,jdbcType=INTEGER}
</if>
<if test="name != null" >
and name = #{name,jdbcType=VARCHAR}
</if>
</sql>
<!-- 分页查询语句 -->
<select id="pageByConditions" resultMap="BaseResultMap">
SELECT
<include refid="Base_Column_List" />
FROM
<include refid="tableName" />
WHERE 1=1
<include refid="Base_Search_Param" />
</select>
ok,以上都是mybatis的基本操作，就不做多余解释。
三.创建拦截器：
我们需要做的是创建一个拦截器（PageInterceptor）、一个执行者(PageExecutor)。
1.PageInteceptor:实现Inteceptor接口，将PageExecutor进行执行，拦截sql添加分页sql（limit xx,xx）
2.PageExecutor:实现Executor接口，在查询时，添加查询总数并修改返回值类型。因为要做的是分页，是查询操作，所以里边的非查询方法都使用基本的实现，只修改两个query方法。
PageInteceptor完整代码：
import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.util.Properties;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
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.factory.DefaultObjectFactory;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
@Intercepts({
@Signature(method = "query", type = Executor.class, args = { MappedStatement.class, Object.class,
RowBounds.class, ResultHandler.class }),
@Signature(method = "prepare", type = StatementHandler.class, args = { Connection.class }) })
public class PageInterceptor implements Interceptor {
private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
private String pattern = "^.*page.*$"; // 需要进行分页操作的字符串正则表达式
public String getPattern() {
return pattern;
}
public void setPattern(String pattern) {
this.pattern = pattern;
}
@Override
public Object intercept(Invocation invocation) throws Throwable {
if (invocation.getTarget() instanceof StatementHandler) {
return handleStatementHandler(invocation);
}
return invocation.proceed();
}
/**
* @param invocation
* @return
* @throws IllegalAccessException
* @throws InvocationTargetException
*/
private Object handleStatementHandler(Invocation invocation)
throws InvocationTargetException, IllegalAccessException {
StatementHandler statementHandler = (StatementHandler) invocation
.getTarget();
MetaObject metaStatementHandler = MetaObject.forObject(
statementHandler, DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY);
RowBounds rowBounds = (RowBounds) metaStatementHandler
.getValue("delegate.rowBounds");
if (rowBounds == null || (rowBounds.getOffset() == RowBounds.NO_ROW_OFFSET && rowBounds
.getLimit() == RowBounds.NO_ROW_LIMIT)) {
return invocation.proceed();
}
// 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环可以分离出最原始的的目标类)
while (metaStatementHandler.hasGetter("h")) {
Object object = metaStatementHandler.getValue("h");
metaStatementHandler = MetaObject.forObject(object,
DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY);
}
// 分离最后一个代理对象的目标类
while (metaStatementHandler.hasGetter("target")) {
Object object = metaStatementHandler.getValue("target");
metaStatementHandler = MetaObject.forObject(object,
DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY);
}
// 将mybatis的内存分页，调整为物理分页
BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
String sql = boundSql.getSql();
// 重写sql
String pageSql = sql + " LIMIT " + rowBounds.getOffset() + "," + rowBounds.getLimit();
metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
// 采用物理分页后，就不需要mybatis的内存分页了，所以重置下面的两个参数
metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
// 将执行权交给下一个拦截器
return invocation.proceed();
}
@Override
public Object plugin(Object o) {
if (Executor.class.isAssignableFrom(o.getClass())) {
PageExecutor executor = new PageExecutor((Executor)o, pattern);
return Plugin.wrap(executor, this);
} else if (o instanceof StatementHandler) {
return Plugin.wrap(o, this);
}
return o;
}
@Override
public void setProperties(Properties properties) {
}
}
PageExecutor完整代码：
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.ibatis.cache.CacheKey;
import org.apache.ibatis.executor.BatchResult;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.transaction.Transaction;
public class PageExecutor implements Executor {
private Executor executor;
private String pattern;
public PageExecutor(Executor executor, String pattern) {
this.executor = executor;
this.pattern = pattern;
}
@Override
public int update(MappedStatement ms, Object parameter) throws SQLException {
return executor.update(ms, parameter);
}
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler,
CacheKey cacheKey, BoundSql boundSql) throws SQLException {
RowBounds rb = new RowBounds(rowBounds.getOffset(), rowBounds.getLimit());
List<E> rows = executor.query(ms, parameter, rowBounds, resultHandler,
cacheKey, boundSql);
return pageResolver(rows, ms, parameter, rb);
}
/**
* 修改返回值类型
* @param rows
* @param ms
* @param parameter
* @param rowBounds
* @return
*/
private <E> List<E> pageResolver(List<E> rows, MappedStatement ms,
Object parameter, RowBounds rowBounds) {
String msid = ms.getId();
// 如果需要分页查询，修改返回类型为Page对象
if (msid.matches(pattern)) {
int count = getCount(ms, parameter);
int offset = rowBounds.getOffset();
int pagesize = rowBounds.getLimit();
return new Page<E>(offset/pagesize + 1, pagesize, count, rows);
}
return rows;
}
/**
* 获取总数
* @param ms
* @param parameter
* @return
*/
private int getCount(MappedStatement ms, Object parameter) {
BoundSql bsql = ms.getBoundSql(parameter);
String sql = bsql.getSql();
String countSql = getCountSql(sql);
Connection connection = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
connection = ms.getConfiguration().getEnvironment().getDataSource()
.getConnection();
stmt = connection.prepareStatement(countSql);
rs = stmt.executeQuery();
if (rs.next())
return rs.getInt(1);
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (connection != null && !connection.isClosed()) {
connection.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
return 0;
}
private String getCountSql(String sql) {
String countHql = " SELECT count(*) "
+ removeSelect(removeOrders(sql));
return countHql;
}
protected String removeOrders(String sql) {
Pattern p = Pattern.compile("ORDER\\s*by[\\w|\\W|\\s|\\S]*", Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(sql);
StringBuffer sb = new StringBuffer();
while (m.find()) {
m.appendReplacement(sb, "");
}
m.appendTail(sb);
return sb.toString();
}
// 去除sql语句中select子句
private static String removeSelect(String hql) {
int beginPos = hql.toLowerCase().indexOf("from");
if (beginPos < 0) {
throw new IllegalArgumentException(" hql : " + hql + " must has a keyword 'from'");
}
return hql.substring(beginPos);
}
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler)
throws SQLException {
BoundSql boundSql = ms.getBoundSql(parameter);
return query(ms, parameter, rowBounds, resultHandler,
executor.createCacheKey(ms, parameter, rowBounds, boundSql),
boundSql);
}
@Override
public List<BatchResult> flushStatements() throws SQLException {
return executor.flushStatements();
}
@Override
public void commit(boolean required) throws SQLException {
executor.commit(required);
}
@Override
public void rollback(boolean required) throws SQLException {
executor.rollback(required);
}
@Override
public CacheKey createCacheKey(MappedStatement ms, Object parameterObject,
RowBounds rowBounds, BoundSql boundSql) {
return executor
.createCacheKey(ms, parameterObject, rowBounds, boundSql);
}
@Override
public boolean isCached(MappedStatement ms, CacheKey key) {
return executor.isCached(ms, key);
}
@Override
public void clearLocalCache() {
executor.clearLocalCache();
}
@Override
public void deferLoad(MappedStatement ms, MetaObject resultObject,
String property, CacheKey key, Class<?> targetType) {
executor.deferLoad(ms, resultObject, property, key, targetType);
}
@Override
public Transaction getTransaction() {
return executor.getTransaction();
}
@Override
public void close(boolean forceRollback) {
executor.close(forceRollback);
}
@Override
public boolean isClosed() {
return executor.isClosed();
}
}
关于Page需要实现List接口的原因：可以看到，query方法返回值是List<E>,而我们现在要在dao中使用Page<E>对象来接收mybatis返回的结果，所以需要让Page实现List接口。
分页查询执行顺序：进入PageInterceptor的plugin方法，拦截到执行者，进入PageExecutor的query方法，执行executor.query()时，又再次回到PageInterceptor的plugin方法，这次会执行
进入intercept方法，将执行的sql拼接上分页限制语句，然后查询出数据结果集合。executor.query()执行完成后，继续执行pageResolver，如果方法名称和配置的需要执行分页操作的字符串匹配时，查询数据总量，并返回Page对象；如果不匹配，直接返回List对象。
四.xml配置：
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="configLocation" value="classpath:/conf/mybatis/mybaties-config.xml"></property> <property name="mapperLocations"> <list> <value>classpath:/conf/mybatis/**/*-mapper.xml</value> </list> </property> <property name="plugins"> <list> <ref bean="pageInterceptor"/> </list> </property> </bean> <bean id="pageInterceptor" class="cn.com.common.PageInterceptor"> <property name="pattern" value="^.*page.*$"></property> </bean>
五.测试代码：
@Test
public void testPage() {
int pageNo = 1;
int pageSize = 10;
RowBounds bounds = new RowBounds((pageNo - 1) * pageSize, pageSize);
Model record = new Model();
Page<Model> list = modelMapper.pageByConditions(bounds, record);
}
本文主要介绍了Mybatis拦截器实现分页的步骤与方法。具有很好的参考价值，下面跟着小编一起来看下吧