mybatis框架的兩種分頁
阿新 • • 發佈：2019-01-23
mybatis有兩種分頁方法
1、記憶體分頁，也就是假分頁。本質是查出所有的資料然後根據遊標的方式，擷取需要的記錄。如果資料量大，開銷大和記憶體溢位。
使用方式：
利用自動生成的example類，加入mybatis的RowBounds類,在呼叫的介面中新增給類的引數
@Override public List<UserVo> selectSelective(UserVo userVo) { List<UserVo> listVo = new ArrayList<UserVo>(); UserPoExample example = new UserPoExample(); /** * 使用mybatis的RowBounds類，該類構造方法中要設定兩個int型別引數 * 第一個是從該條記錄開始，第二個是開始後查詢的條數 */ <strong>RowBounds rowBounds = new RowBounds(0, 5);</strong> Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("123"); criteria.andRoleEqualTo(userVo.getRole()); example.setOrderByClause("userId desc");//設定排序方式 example.setStart(10); example.setLimit(10); UserPo userPo = new UserPo(); userPo.setUsername("123"); userPo.setRole(1); Page<UserVo> page = new Page<UserVo>(); List<UserPo> listPo =null; try { //int countByExample = userPoMapper.countByExample(example);//按照條件查詢總數 //listPo = userPoMapper.selectBySelective(userPo,page); listPo = userPoMapper.selectByExample(example,<strong>rowBounds</strong>); for(UserPo po:listPo){ UserVo vo = new UserVo(); BeanUtils.copyProperties(po, vo); listVo.add(vo); } } catch (Exception e) { logger.error(e); } return listVo; }
第二中是，真正的物理分頁
在自動生成的example物件中，加入兩個成員變數start、和limit
public class UserPoExample { <strong>private int start;//設定分頁開始 private int limit;//設定分頁的每頁的數量</strong> public int getStart() { return start; } public void setStart(int start) { this.start = start; } public int getLimit() { return limit; } public void setLimit(int limit) { this.limit = limit; }
最後在對應的xml的方法中新增剛剛加入的條件，直接新增在自動生成的orderByClause後面
<if test="orderByClause != null" > order by ${orderByClause} </if> <strong><if test="start !=0 or limit!=0"> limit #{start},#{limit}</if><span style="font-family: Arial, Helvetica, sans-serif;"> </span></strong>
通過日誌可以看到是真正的分頁查詢
還有一種是使用分頁攔截器實現的
首先在spring-dao的sqlsession工廠裡面配置攔截器
<!-- sqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<!-- 資料庫連線池 -->
<property name="dataSource" ref="dataSource" />
<!-- 批量掃描別名 -->
<property name="typeAliasesPackage" value="ssm.po" />
<!-- spring與mybatis整合不需要mybatis配置檔案了,直接掃描mapper下的對映檔案 -->
<property name="mapperLocations" value="classpath:ssm/mapper/*.xml" />
<!-- MybatisSpringPageInterceptor分頁攔截器 -->
<property name="plugins">
<bean class="ssm.utils.MybatisSpringPageInterceptor"></bean>
</property>
</bean>攔截器程式碼：
package ssm.utils;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import org.apache.ibatis.executor.Executor;
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.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.scripting.defaults.DefaultParameterHandler;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@Intercepts({ @Signature(method = "prepare", type = StatementHandler.class, args = { Connection.class }),
@Signature(method = "query", type = Executor.class, args = { MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class }) })
public class MybatisSpringPageInterceptor implements Interceptor {
private static final Logger log = LoggerFactory.getLogger(MybatisSpringPageInterceptor.class);
public static final String MYSQL = "mysql";
public static final String ORACLE = "oracle";
protected String databaseType;// 資料庫型別，不同的資料庫有不同的分頁方法
@SuppressWarnings("rawtypes")
protected ThreadLocal<Page> pageThreadLocal = new ThreadLocal<Page>();
public String getDatabaseType() {
return databaseType;
}
public void setDatabaseType(String databaseType) {
if (!databaseType.equalsIgnoreCase(MYSQL) && !databaseType.equalsIgnoreCase(ORACLE)) {
throw new PageNotSupportException("Page not support for the type of database, database type [" + databaseType + "]");
}
this.databaseType = databaseType;
}
@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
@Override
public void setProperties(Properties properties) {
String databaseType = properties.getProperty("databaseType");
if (databaseType != null) {
setDatabaseType(databaseType);
}
}
@Override
@SuppressWarnings({ "unchecked", "rawtypes" })
public Object intercept(Invocation invocation) throws Throwable {
if (invocation.getTarget() instanceof StatementHandler) { // 控制SQL和查詢總數的地方
Page page = pageThreadLocal.get();
if (page == null) { //不是分頁查詢
return invocation.proceed();
}
RoutingStatementHandler handler = (RoutingStatementHandler) invocation.getTarget();
StatementHandler delegate = (StatementHandler) ReflectUtil.getFieldValue(handler, "delegate");
BoundSql boundSql = delegate.getBoundSql();
Connection connection = (Connection) invocation.getArgs()[0];
prepareAndCheckDatabaseType(connection); // 準備資料庫型別
if (page.getTotalPage() > -1) {
if (log.isTraceEnabled()) {
log.trace("已經設定了總頁數, 不需要再查詢總數.");
}
} else {
Object parameterObj = boundSql.getParameterObject();
MappedStatement mappedStatement = (MappedStatement) ReflectUtil.getFieldValue(delegate, "mappedStatement");
queryTotalRecord(page, parameterObj, mappedStatement, connection);
}
String sql = boundSql.getSql();
String pageSql = buildPageSql(page, sql);
if (log.isDebugEnabled()) {
log.debug("分頁時, 生成分頁pageSql: " + pageSql);
}
ReflectUtil.setFieldValue(boundSql, "sql", pageSql);
return invocation.proceed();
} else { // 查詢結果的地方
// 獲取是否有分頁Page物件
Page<?> page = findPageObject(invocation.getArgs()[1]);
if (page == null) {
if (log.isTraceEnabled()) {
log.trace("沒有Page物件作為引數, 不是分頁查詢.");
}
return invocation.proceed();
} else {
if (log.isTraceEnabled()) {
log.trace("檢測到分頁Page物件, 使用分頁查詢.");
}
}
//設定真正的parameterObj
invocation.getArgs()[1] = extractRealParameterObject(invocation.getArgs()[1]);
pageThreadLocal.set(page);
try {
Object resultObj = invocation.proceed(); // Executor.query(..)
if (resultObj instanceof List) {
/* @SuppressWarnings({ "unchecked", "rawtypes" }) */
page.setResults((List) resultObj);
}
return resultObj;
} finally {
pageThreadLocal.remove();
}
}
}
protected Page<?> findPageObject(Object parameterObj) {
if (parameterObj instanceof Page<?>) {
return (Page<?>) parameterObj;
} else if (parameterObj instanceof Map) {
for (Object val : ((Map<?, ?>) parameterObj).values()) {
if (val instanceof Page<?>) {
return (Page<?>) val;
}
}
}
return null;
}
/**
* <pre>
* 把真正的引數物件解析出來
* Spring會自動封裝對個引數物件為Map<String, Object>物件
* 對於通過@Param指定key值引數我們不做處理，因為XML檔案需要該KEY值
* 而對於沒有@Param指定時，Spring會使用0,1作為主鍵
* 對於沒有@Param指定名稱的引數,一般XML檔案會直接對真正的引數物件解析，
* 此時解析出真正的引數作為根物件
* </pre>
* @param parameterObj
* @return
*/
protected Object extractRealParameterObject(Object parameterObj) {
if (parameterObj instanceof Map<?, ?>) {
Map<?, ?> parameterMap = (Map<?, ?>) parameterObj;
if (parameterMap.size() == 2) {
boolean springMapWithNoParamName = true;
for (Object key : parameterMap.keySet()) {
if (!(key instanceof String)) {
springMapWithNoParamName = false;
break;
}
String keyStr = (String) key;
if (!"0".equals(keyStr) && !"1".equals(keyStr)) {
springMapWithNoParamName = false;
break;
}
}
if (springMapWithNoParamName) {
for (Object value : parameterMap.values()) {
if (!(value instanceof Page<?>)) {
return value;
}
}
}
}
}
return parameterObj;
}
protected void prepareAndCheckDatabaseType(Connection connection) throws SQLException {
if (databaseType == null) {
String productName = connection.getMetaData().getDatabaseProductName();
if (log.isTraceEnabled()) {
log.trace("Database productName: " + productName);
}
productName = productName.toLowerCase();
if (productName.indexOf(MYSQL) != -1) {
databaseType = MYSQL;
} else if (productName.indexOf(ORACLE) != -1) {
databaseType = ORACLE;
} else {
throw new PageNotSupportException("Page not support for the type of database, database product name [" + productName + "]");
}
if (log.isInfoEnabled()) {
log.info("自動檢測到的資料庫型別為: " + databaseType);
}
}
}
/**
* <pre>
* 生成分頁SQL
* </pre>
*
* @param page
* @param sql
* @return
*/
protected String buildPageSql(Page<?> page, String sql) {
if (MYSQL.equalsIgnoreCase(databaseType)) {
return buildMysqlPageSql(page, sql);
} else if (ORACLE.equalsIgnoreCase(databaseType)) {
return buildOraclePageSql(page, sql);
}
return sql;
}
/**
* <pre>
* 生成Mysql分頁查詢SQL
* </pre>
*
* @param page
* @param sql
* @return
*/
protected String buildMysqlPageSql(Page<?> page, String sql) {
// 計算第一條記錄的位置，Mysql中記錄的位置是從0開始的。
int offset = (page.getPageNo() - 1) * page.getPageSize();
return new StringBuilder(sql).append(" limit ").append(offset).append(",").append(page.getPageSize()).toString();
}
/**
* <pre>
* 生成Oracle分頁查詢SQL
* </pre>
*
* @param page
* @param sql
* @return
*/
protected String buildOraclePageSql(Page<?> page, String sql) {
// 計算第一條記錄的位置，Oracle分頁是通過rownum進行的，而rownum是從1開始的
int offset = (page.getPageNo() - 1) * page.getPageSize() + 1;
StringBuilder sb = new StringBuilder(sql);
sb.insert(0, "select u.*, rownum r from (").append(") u where rownum < ").append(offset + page.getPageSize());
sb.insert(0, "select * from (").append(") where r >= ").append(offset);
return sb.toString();
}
/**
* <pre>
* 查詢總數
* </pre>
*
* @param page
* @param parameterObject
* @param mappedStatement
* @param connection
* @throws SQLException
*/
protected void queryTotalRecord(Page<?> page, Object parameterObject, MappedStatement mappedStatement, Connection connection) throws SQLException {
BoundSql boundSql = mappedStatement.getBoundSql(page);
String sql = boundSql.getSql();
String countSql = this.buildCountSql(sql);
if (log.isDebugEnabled()) {
log.debug("分頁時, 生成countSql: " + countSql);
}
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
BoundSql countBoundSql = new BoundSql(mappedStatement.getConfiguration(), countSql, parameterMappings, parameterObject);
ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, countBoundSql);
PreparedStatement pstmt = null;
ResultSet rs = null;
try {
pstmt = connection.prepareStatement(countSql);
parameterHandler.setParameters(pstmt);
rs = pstmt.executeQuery();
if (rs.next()) {
long totalRecord = rs.getLong(1);
page.setTotalRecord(totalRecord);
}
} finally {
if (rs != null)
try {
rs.close();
} catch (Exception e) {
if (log.isWarnEnabled()) {
log.warn("關閉ResultSet時異常.", e);
}
}
if (pstmt != null)
try {
pstmt.close();
} catch (Exception e) {
if (log.isWarnEnabled()) {
log.warn("關閉PreparedStatement時異常.", e);
}
}
}
}
/**
* 根據原Sql語句獲取對應的查詢總記錄數的Sql語句
*
* @param sql
* @return
*/
protected String buildCountSql(String sql) {
int index = sql.indexOf("from");
return "select count(*) " + sql.substring(index);
}
/**
* 利用反射進行操作的一個工具類
*
*/
private static class ReflectUtil {
/**
* 利用反射獲取指定物件的指定屬性
*
* @param obj 目標物件
* @param fieldName 目標屬性
* @return 目標屬性的值
*/
public static Object getFieldValue(Object obj, String fieldName) {
Object result = null;
Field field = ReflectUtil.getField(obj, fieldName);
if (field != null) {
field.setAccessible(true);
try {
result = field.get(obj);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return result;
}
/**
* 利用反射獲取指定物件裡面的指定屬性
*
* @param obj 目標物件
* @param fieldName 目標屬性
* @return 目標欄位
*/
private static Field getField(Object obj, String fieldName) {
Field field = null;
for (Class<?> clazz = obj.getClass(); clazz != Object.class; clazz = clazz.getSuperclass()) {
try {
field = clazz.getDeclaredField(fieldName);
break;
} catch (NoSuchFieldException e) {
// 這裡不用做處理，子類沒有該欄位可能對應的父類有，都沒有就返回null。
}
}
return field;
}
/**
* 利用反射設定指定物件的指定屬性為指定的值
*
* @param obj 目標物件
* @param fieldName 目標屬性
* @param fieldValue 目標值
*/
public static void setFieldValue(Object obj, String fieldName, String fieldValue) {
Field field = ReflectUtil.getField(obj, fieldName);
if (field != null) {
try {
field.setAccessible(true);
field.set(obj, fieldValue);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
public static class PageNotSupportException extends RuntimeException {
/** serialVersionUID*/
private static final long serialVersionUID = 1L;
public PageNotSupportException() {
super();
}
public PageNotSupportException(String message, Throwable cause) {
super(message, cause);
}
public PageNotSupportException(String message) {
super(message);
}
public PageNotSupportException(Throwable cause) {
super(cause);
}
}
}
分頁的Page物件：
package ssm.utils;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Page<T> {
public static final int DEFAULT_PAGE_SIZE = 10;
protected int pageNo = 1; // 當前頁, 預設為第1頁
protected int pageSize = DEFAULT_PAGE_SIZE; // 每頁記錄數
protected long totalRecord = -1; // 總記錄數, 預設為-1, 表示需要查詢
protected int totalPage = -1; // 總頁數, 預設為-1, 表示需要計算
protected List<T> results; // 當前頁記錄List形式
public Map<String, Object> params = new HashMap<String, Object>();//設定頁面傳遞的查詢引數
public Map<String, Object> getParams() {
return params;
}
public void setParams(Map<String, Object> params) {
this.params = params;
}
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;
computeTotalPage();
}
public long getTotalRecord() {
return totalRecord;
}
public int getTotalPage() {
return totalPage;
}
public void setTotalRecord(long totalRecord) {
this.totalRecord = totalRecord;
computeTotalPage();
}
protected void computeTotalPage() {
if (getPageSize() > 0 && getTotalRecord() > -1) {
this.totalPage = (int) (getTotalRecord() % getPageSize() == 0 ? getTotalRecord() / getPageSize() : getTotalRecord() / getPageSize() + 1);
}
}
public List<T> getResults() {
return results;
}
public void setResults(List<T> results) {
this.results = results;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder().append("Page [pageNo=").append(pageNo).append(", pageSize=").append(pageSize)
.append(", totalRecord=").append(totalRecord < 0 ? "null" : totalRecord).append(", totalPage=")
.append(totalPage < 0 ? "null" : totalPage).append(", curPageObjects=").append(results == null ? "null" : results.size()).append("]");
return builder.toString();
}
}
ServiceImpl呼叫過程：最後查詢出來的分頁的資訊
@Override
public List<UserVo> selectSelective(UserVo userVo) {
List<UserVo> listVo = new ArrayList<UserVo>();
// UserPoExample example = new UserPoExample();
// Criteria criteria = example.createCriteria();
// criteria.andUsernameEqualTo(userVo.getUsername());
// criteria.andRoleEqualTo(userVo.getRole());
// example.setOrderByClause("userId desc");//設定排序方式
// example.setStart(0);
// example.setLimit(10);
Page<UserVo> page = new Page<UserVo>();
List<UserPo> listPo =null;
try {
// UserPo po1 = new UserPo();
// po1.setUsername(userVo.getUsername());
// po1.setRole(userVo.getRole());
Map<String, Object> params = new HashMap<String, Object>();
params.put("username", userVo.getUsername());
params.put("role", userVo.getRole());
params.put("orderByClause","userId desc");
page.setParams(params);
listPo = userPoMapper.selectBySelective(page);
for(UserPo po:listPo){
UserVo vo = new UserVo();
BeanUtils.copyProperties(po, vo);
listVo.add(vo);
}
page.setResults(listVo);
} catch (Exception e) {
logger.error(e);
}
return listVo;
}對應的xml
<select id="selectBySelective" parameterType="ssm.utils.Page" resultType="ssm.po.UserPo">
select * from tb_user
<where>
<if test="params.username != null and params.username !=''">
userName = #{params.username}
<!-- userName like '%${usesrname}%' -->
</if>
<if test="params.password != null and params.password !=''">
and password = #{params.password}
</if>
<if test="params.sex != null and params.sex !=''">
and sex = #{params.sex}
</if>
<if test="params.age != null and params.age !=''">
and age = #{params.age}
</if>
<if test="params.email != null and params.email !=''">
and email = #{params.email}
</if>
<if test="params.courseid != null and params.courseid !=''">
and courseId = #{params.courseid}
</if>
<if test="params.role != null and params.role !=''">
and role = #{params.role}
</if>
<if test="params.state != null and params.state !=''">
and state = #{params.state}
</if>
</where>
<if test="params.orderByClause != null and params.orderByClause !=''"></if>
order by #{params.orderByClause}
</select>