MyBatis分页插件
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本方法是通过拦截mybatis底层的数据库操作达到分页目的
- //分页实体类
- public class Page {
- private int showCount = 10 ; //每页显示记录数
- private int totalPage; //总页数
- private int totalResult; //总记录数
- private int currentPage; //当前页
- private int currentResult; //当前记录起始索引
- private boolean entityOrField; //true:需要分页的地方,传入的参数就是Page实体;false:需要分页的地方,传入的参数所代表的实体拥有Page属性
- private String pageStr; //最终页面显示的底部翻页导航,详细见:getPageStr();
- public int getTotalPage() {
- if (totalResult%showCount== 0 )
- totalPage = totalResult/showCount;
- else
- totalPage = totalResult/showCount+1 ;
- return totalPage;
- }
- public void setTotalPage( int totalPage) {
- this .totalPage = totalPage;
- }
- public int getTotalResult() {
- return totalResult;
- }
- public void setTotalResult( int totalResult) {
- this .totalResult = totalResult;
- }
- public int getCurrentPage() {
- if (currentPage<= 0 )
- currentPage = 1 ;
- if (currentPage>getTotalPage())
- currentPage = getTotalPage();
- return currentPage;
- }
- public void setCurrentPage( int currentPage) {
- this .currentPage = currentPage;
- }
- public String getPageStr() {
- StringBuffer sb = new StringBuffer();
- if (totalResult> 0 ){
- sb.append(" <ul>\n" );
- if (currentPage== 1 ){
- sb.append(" <li class=\"pageinfo\">首页</li>\n" );
- sb.append(" <li class=\"pageinfo\">上页</li>\n" );
- }else {
- sb.append(" <li><a href=\"#@\" onclick=\"nextPage(1)\">首页</a></li>\n" );
- sb.append(" <li><a href=\"#@\" onclick=\"nextPage(" +(currentPage- 1 )+ ")\">上页</a></li>\n" );
- }
- int showTag = 3 ; //分页标签显示数量
- int startTag = 1 ;
- if (currentPage>showTag){
- startTag = currentPage-1 ;
- }
- int endTag = startTag+showTag- 1 ;
- for ( int i=startTag; i<=totalPage && i<=endTag; i++){
- if (currentPage==i)
- sb.append("<li class=\"current\">" +i+ "</li>\n" );
- else
- sb.append(" <li><a href=\"#@\" onclick=\"nextPage(" +i+ ")\">" +i+ "</a></li>\n" );
- }
- if (currentPage==totalPage){
- sb.append(" <li class=\"pageinfo\">下页</li>\n" );
- sb.append(" <li class=\"pageinfo\">尾页</li>\n" );
- }else {
- sb.append(" <li><a href=\"#@\" onclick=\"nextPage(" +(currentPage+ 1 )+ ")\">下页</a></li>\n" );
- sb.append(" <li><a href=\"#@\" onclick=\"nextPage(" +totalPage+ ")\">尾页</a></li>\n" );
- }
- sb.append(" <li class=\"pageinfo\">第" +currentPage+ "页</li>\n" );
- sb.append(" <li class=\"pageinfo\">共" +totalPage+ "页</li>\n" );
- sb.append("</ul>\n" );
- sb.append("<script type=\"text/javascript\">\n" );
- sb.append("function nextPage(page){" );
- sb.append(" if(true && document.forms[0]){\n" );
- sb.append(" var url = document.forms[0].getAttribute(\"action\");\n" );
- sb.append(" if(url.indexOf('?')>-1){url += \"&" +(entityOrField? "currentPage" : "page.currentPage" )+ "=\";}\n" );
- sb.append(" else{url += \"?" +(entityOrField? "currentPage" : "page.currentPage" )+ "=\";}\n" );
- sb.append(" document.forms[0].action = url+page;\n" );
- sb.append(" document.forms[0].submit();\n" );
- sb.append(" }else{\n" );
- sb.append(" var url = document.location+';\n" );
- sb.append(" if(url.indexOf('?')>-1){\n" );
- sb.append(" if(url.indexOf('currentPage')>-1){\n" );
- sb.append(" var reg = /currentPage=\\d*/g;\n" );
- sb.append(" url = url.replace(reg,'currentPage=');\n" );
- sb.append(" }else{\n" );
- sb.append(" url += \"&" +(entityOrField? "currentPage" : "page.currentPage" )+ "=\";\n" );
- sb.append(" }\n" );
- sb.append(" }else{url += \"?" +(entityOrField? "currentPage" : "page.currentPage" )+ "=\";}\n" );
- sb.append(" document.location = url + page;\n" );
- sb.append(" }\n" );
- sb.append("}\n" );
- sb.append("</script>\n" );
- }
- pageStr = sb.toString();
- return pageStr;
- }
- public void setPageStr(String pageStr) {
- this .pageStr = pageStr;
- }
- public int getShowCount() {
- return showCount;
- }
- public void setShowCount( int showCount) {
- this .showCount = showCount;
- }
- public int getCurrentResult() {
- currentResult = (getCurrentPage()-1 )*getShowCount();
- if (currentResult< 0 )
- currentResult = 0 ;
- return currentResult;
- }
- public void setCurrentResult( int currentResult) {
- this .currentResult = currentResult;
- }
- public boolean isEntityOrField() {
- return entityOrField;
- }
- public void setEntityOrField( boolean entityOrField) {
- this .entityOrField = entityOrField;
- }
- }
通过拦截StatementHandler的prepare方法的分页插件类
- @Intercepts ({ @Signature (type=StatementHandler. class ,method= "prepare" ,args={Connection. class })})
- public class PagePlugin implements Interceptor {
- private static String dialect = "" ; //数据库方言
- private static String pageSqlId = "" ; //mapper.xml中需要拦截的ID(正则匹配)
- public Object intercept(Invocation ivk) throws Throwable {
- // TODO Auto-generated method stub
- if (ivk.getTarget() instanceof RoutingStatementHandler){
- RoutingStatementHandler statementHandler = (RoutingStatementHandler)ivk.getTarget();
- BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler, "delegate" );
- MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByFieldName(delegate, "mappedStatement" );
- if (mappedStatement.getId().matches(pageSqlId)){ //拦截需要分页的SQL
- BoundSql boundSql = delegate.getBoundSql();
- Object parameterObject = boundSql.getParameterObject();//分页SQL<select>中parameterType属性对应的实体参数,即Mapper接口中执行分页方法的参数,该参数不得为空
- if (parameterObject== null ){
- throw new NullPointerException( "parameterObject尚未实例化!" );
- }else {
- Connection connection = (Connection) ivk.getArgs()[0 ];
- String sql = boundSql.getSql();
- String countSql = "select count(0) from (" + sql+ ") as tmp_count" ; //记录统计
- PreparedStatement countStmt = connection.prepareStatement(countSql);
- //BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(),countSql,boundSql.getParameterMappings(),parameterObject);
- setParameters(countStmt,mappedStatement,boundSql,parameterObject);
- ResultSet rs = countStmt.executeQuery();
- int count = 0 ;
- if (rs.next()) {
- count = rs.getInt(1 );
- }
- rs.close();
- countStmt.close();
- //System.out.println(count);
- Page page = null ;
- if (parameterObject instanceof Page){ //参数就是Page实体
- page = (Page) parameterObject;
- page.setEntityOrField(true ); //见com.flf.entity.Page.entityOrField 注释
- page.setTotalResult(count);
- }else { //参数为某个实体,该实体拥有Page属性
- Field pageField = ReflectHelper.getFieldByFieldName(parameterObject,"page" );
- if (pageField!= null ){
- page = (Page) ReflectHelper.getValueByFieldName(parameterObject,"page" );
- if (page== null )
- page = new Page();
- page.setEntityOrField(false ); //见com.flf.entity.Page.entityOrField 注释
- page.setTotalResult(count);
- ReflectHelper.setValueByFieldName(parameterObject,"page" , page); //通过反射,对实体对象设置分页对象
- }else {
- throw new NoSuchFieldException(parameterObject.getClass().getName()+ "不存在 page 属性!" );
- }
- }
- String pageSql = generatePageSql(sql,page);
- ReflectHelper.setValueByFieldName(boundSql, "sql" , pageSql); //将分页sql语句反射回BoundSql.
- }
- }
- }
- return ivk.proceed();
- }
- /**
- * 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler
- * @param ps
- * @param mappedStatement
- * @param boundSql
- * @param parameterObject
- * @throws SQLException
- */
- private void setParameters(PreparedStatement ps,MappedStatement mappedStatement,BoundSql boundSql,Object parameterObject) throws SQLException {
- ErrorContext.instance().activity("setting parameters" ).object(mappedStatement.getParameterMap().getId());
- List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
- if (parameterMappings != null ) {
- Configuration configuration = mappedStatement.getConfiguration();
- TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
- MetaObject metaObject = parameterObject == null ? null : configuration.newMetaObject(parameterObject);
- for ( int i = 0 ; i < parameterMappings.size(); i++) {
- ParameterMapping parameterMapping = parameterMappings.get(i);
- if (parameterMapping.getMode() != ParameterMode.OUT) {
- Object value;
- String propertyName = parameterMapping.getProperty();
- PropertyTokenizer prop = new PropertyTokenizer(propertyName);
- if (parameterObject == null ) {
- value = null ;
- } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
- value = parameterObject;
- } else if (boundSql.hasAdditionalParameter(propertyName)) {
- value = boundSql.getAdditionalParameter(propertyName);
- } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)&& boundSql.hasAdditionalParameter(prop.getName())) {
- value = boundSql.getAdditionalParameter(prop.getName());
- if (value != null ) {
- value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));
- }
- } else {
- value = metaObject == null ? null : metaObject.getValue(propertyName);
- }
- TypeHandler typeHandler = parameterMapping.getTypeHandler();
- if (typeHandler == null ) {
- throw new ExecutorException( "There was no TypeHandler found for parameter " + propertyName + " of statement " + mappedStatement.getId());
- }
- typeHandler.setParameter(ps, i + 1 , value, parameterMapping.getJdbcType());
- }
- }
- }
- }
- /**
- * 根据数据库方言,生成特定的分页sql
- * @param sql
- * @param page
- * @return
- */
- private String generatePageSql(String sql,Page page){
- if (page!= null && Tools.notEmpty(dialect)){
- StringBuffer pageSql = new StringBuffer();
- if ( "mysql" .equals(dialect)){
- pageSql.append(sql);
- pageSql.append(" limit " +page.getCurrentResult()+ "," +page.getShowCount());
- }else if ( "oracle" .equals(dialect)){
- pageSql.append("select * from (select tmp_tb.*,ROWNUM row_id from (" );
- pageSql.append(sql);
- pageSql.append(") as tmp_tb where ROWNUM<=" );
- pageSql.append(page.getCurrentResult()+page.getShowCount());
- pageSql.append(") where row_id>" );
- pageSql.append(page.getCurrentResult());
- }
- return pageSql.toString();
- }else {
- return sql;
- }
- }
- public Object plugin(Object arg0) {
- // TODO Auto-generated method stub
- return Plugin.wrap(arg0, this );
- }
- public void setProperties(Properties p) {
- dialect = p.getProperty("dialect" );
- if (Tools.isEmpty(dialect)) {
- try {
- throw new PropertyException( "dialect property is not found!" );
- } catch (PropertyException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- pageSqlId = p.getProperty("pageSqlId" );
- if (Tools.isEmpty(pageSqlId)) {
- try {
- throw new PropertyException( "pageSqlId property is not found!" );
- } catch (PropertyException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- }
- }
该类中定义了两个私有静态变量:dialect、pageSqlId,这两个变量是在该类初始化时,即调用setProperties方法时初始化的,相关的值是在MyBatis配置文件中配置的,如下:
- < plugins >
- < plugin interceptor = "com.flf.plugin.PagePlugin" >
- < property name = "dialect" value = "mysql" />
- < property name = "pageSqlId" value = ".*listPage.*" />
- </ plugin >
- </ plugins >
上面的示例表明数据库方言为mysql,拦截所有mapper.xml映射文件中id包含有listPage的SQL。
反射帮助类:
- /**
- * @author Administrator
- * 反射工具
- */
- public class ReflectHelper {
- /**
- * 获取obj对象fieldName的Field
- * @param obj
- * @param fieldName
- * @return
- */
- public static Field getFieldByFieldName(Object obj, String fieldName) {
- for (Class<?> superClass = obj.getClass(); superClass != Object. class ; superClass = superClass
- .getSuperclass()) {
- try {
- return superClass.getDeclaredField(fieldName);
- } catch (NoSuchFieldException e) {
- }
- }
- return null ;
- }
- /**
- * 获取obj对象fieldName的属性值
- * @param obj
- * @param fieldName
- * @return
- * @throws SecurityException
- * @throws NoSuchFieldException
- * @throws IllegalArgumentException
- * @throws IllegalAccessException
- */
- public static Object getValueByFieldName(Object obj, String fieldName)
- throws SecurityException, NoSuchFieldException,
- IllegalArgumentException, IllegalAccessException {
- Field field = getFieldByFieldName(obj, fieldName);
- Object value = null ;
- if (field!= null ){
- if (field.isAccessible()) {
- value = field.get(obj);
- } else {
- field.setAccessible(true );
- value = field.get(obj);
- field.setAccessible(false );
- }
- }
- return value;
- }
- /**
- * 设置obj对象fieldName的属性值
- * @param obj
- * @param fieldName
- * @param value
- * @throws SecurityException
- * @throws NoSuchFieldException
- * @throws IllegalArgumentException
- * @throws IllegalAccessException
- */
- public static void setValueByFieldName(Object obj, String fieldName,
- Object value) throws SecurityException, NoSuchFieldException,
- IllegalArgumentException, IllegalAccessException {
- Field field = obj.getClass().getDeclaredField(fieldName);
- if (field.isAccessible()) {
- field.set(obj, value);
- } else {
- field.setAccessible(true );
- field.set(obj, value);
- field.setAccessible(false );
- }
- }
- }
PS:分页插件类PagePlugin只实现了mysql和oracle的分页,至于其他的数据库,可以修改该类的generatePageSql方法。
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