MyBatis分页

本方法是通过拦截mybatis底层的数据库操作达到分页目的

[java] view plaincopyprint?

1. //分页实体类  

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1. public class Page {  
2.     private int showCount = 10; //每页显示记录数  
3.     private int totalPage;      //总页数  
4.     private int totalResult;    //总记录数  
5.     private int currentPage;    //当前页  
6.     private int currentResult;  //当前记录起始索引  
7.     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  
8.     private String pageStr;     //最终页面显示的底部翻页导航，详细见：getPageStr();  
9.     public int getTotalPage() {  
10.         if(totalResult%showCount==0)  
11.             totalPage = totalResult/showCount;  
12.         else  
13.             totalPage = totalResult/showCount+1;  
14.         return totalPage;  
15.     }  
16.     public void setTotalPage(int totalPage) {  
17.         this.totalPage = totalPage;  
18.     }  
19.     public int getTotalResult() {  
20.         return totalResult;  
21.     }  
22.     public void setTotalResult(int totalResult) {  
23.         this.totalResult = totalResult;  
24.     }  
25.     public int getCurrentPage() {  
26.         if(currentPage<=0)  
27.             currentPage = 1;  
28.         if(currentPage>getTotalPage())  
29.             currentPage = getTotalPage();  
30.         return currentPage;  
31.     }  
32.     public void setCurrentPage(int currentPage) {  
33.         this.currentPage = currentPage;  
34.     }  
35.     public String getPageStr() {  
36.         StringBuffer sb = new StringBuffer();  
37.         if(totalResult>0){  
38.             sb.append(" <ul>\n");  
39.             if(currentPage==1){  
40.                 sb.append(" <li class=\"pageinfo\">首页</li>\n");  
41.                 sb.append(" <li class=\"pageinfo\">上页</li>\n");  
42.             }else{    
43.                 sb.append(" <li><a href=\"#@\" onclick=\"nextPage(1)\">首页</a></li>\n");  
44.                 sb.append(" <li><a href=\"#@\" onclick=\"nextPage("+(currentPage-1)+")\">上页</a></li>\n");  
45.             }  
46.             int showTag = 3;    //分页标签显示数量  
47.             int startTag = 1;  
48.             if(currentPage>showTag){  
49.                 startTag = currentPage-1;  
50.             }  
51.             int endTag = startTag+showTag-1;  
52.             for(int i=startTag; i<=totalPage && i<=endTag; i++){  
53.                 if(currentPage==i)  
54.                     sb.append("<li class=\"current\">"+i+"</li>\n");  
55.                 else  
56.                     sb.append(" <li><a href=\"#@\" onclick=\"nextPage("+i+")\">"+i+"</a></li>\n");  
57.             }  
58.             if(currentPage==totalPage){  
59.                 sb.append(" <li class=\"pageinfo\">下页</li>\n");  
60.                 sb.append(" <li class=\"pageinfo\">尾页</li>\n");  
61.             }else{  
62.                 sb.append(" <li><a href=\"#@\" onclick=\"nextPage("+(currentPage+1)+")\">下页</a></li>\n");  
63.                 sb.append(" <li><a href=\"#@\" onclick=\"nextPage("+totalPage+")\">尾页</a></li>\n");  
64.             }  
65.             sb.append(" <li class=\"pageinfo\">第"+currentPage+"页</li>\n");  
66.             sb.append(" <li class=\"pageinfo\">共"+totalPage+"页</li>\n");  
67.             sb.append("</ul>\n");  
68.             sb.append("<script type=\"text/javascript\">\n");  
69.             sb.append("function nextPage(page){");  
70.             sb.append(" if(true && document.forms[0]){\n");  
71.             sb.append("     var url = document.forms[0].getAttribute(\"action\");\n");  
72.             sb.append("     if(url.indexOf('?')>-1){url += \"&"+(entityOrField?"currentPage":"page.currentPage")+"=\";}\n");  
73.             sb.append("     else{url += \"?"+(entityOrField?"currentPage":"page.currentPage")+"=\";}\n");  
74.             sb.append("     document.forms[0].action = url+page;\n");  
75.             sb.append("     document.forms[0].submit();\n");  
76.             sb.append(" }else{\n");  
77.             sb.append("     var url = document.location+';\n");  
78.             sb.append("     if(url.indexOf('?')>-1){\n");  
79.             sb.append("         if(url.indexOf('currentPage')>-1){\n");  
80.             sb.append("             var reg = /currentPage=\\d*/g;\n");  
81.             sb.append("             url = url.replace(reg,'currentPage=');\n");  
82.             sb.append("         }else{\n");  
83.             sb.append("             url += \"&"+(entityOrField?"currentPage":"page.currentPage")+"=\";\n");  
84.             sb.append("         }\n");  
85.             sb.append("     }else{url += \"?"+(entityOrField?"currentPage":"page.currentPage")+"=\";}\n");  
86.             sb.append("     document.location = url + page;\n");  
87.             sb.append(" }\n");  
88.             sb.append("}\n");  
89.             sb.append("</script>\n");  
90.         }  
91.         pageStr = sb.toString();  
92.         return pageStr;  
93.     }  
94.     public void setPageStr(String pageStr) {  
95.         this.pageStr = pageStr;  
96.     }  
97.     public int getShowCount() {  
98.         return showCount;  
99.     }  
100.     public void setShowCount(int showCount) {  
101.         this.showCount = showCount;  
102.     }  
103.     public int getCurrentResult() {  
104.         currentResult = (getCurrentPage()-1)*getShowCount();  
105.         if(currentResult<0)  
106.             currentResult = 0;  
107.         return currentResult;  
108.     }  
109.     public void setCurrentResult(int currentResult) {  
110.         this.currentResult = currentResult;  
111.     }  
112.     public boolean isEntityOrField() {  
113.         return entityOrField;  
114.     }  
115.     public void setEntityOrField(boolean entityOrField) {  
116.         this.entityOrField = entityOrField;  
117.     }  
118.       

通过拦截StatementHandler的prepare方法的分页插件类

[java] view plaincopyprint?

1. @Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class})})  
2. public class PagePlugin implements Interceptor {  
3.   
4.     private static String dialect = ""; //数据库方言  
5.     private static String pageSqlId = ""; //mapper.xml中需要拦截的ID(正则匹配)  
6.       
7.     public Object intercept(Invocation ivk) throws Throwable {  
8.         // TODO Auto-generated method stub  
9.         if(ivk.getTarget() instanceof RoutingStatementHandler){  
10.             RoutingStatementHandler statementHandler = (RoutingStatementHandler)ivk.getTarget();  
11.             BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler, "delegate");  
12.             MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByFieldName(delegate, "mappedStatement");  
13.               
14.             if(mappedStatement.getId().matches(pageSqlId)){ //拦截需要分页的SQL  
15.                 BoundSql boundSql = delegate.getBoundSql();  
16.                 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  
17.                 if(parameterObject==null){  
18.                     throw new NullPointerException("parameterObject尚未实例化！");  
19.                 }else{  
20.                     Connection connection = (Connection) ivk.getArgs()[0];  
21.                     String sql = boundSql.getSql();  
22.                     String countSql = "select count(0) from (" + sql+ ") as tmp_count"; //记录统计  
23.                     PreparedStatement countStmt = connection.prepareStatement(countSql);  
24.                     BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(),countSql,boundSql.getParameterMappings(),parameterObject);  
25.                     setParameters(countStmt,mappedStatement,countBS,parameterObject);  
26.                     ResultSet rs = countStmt.executeQuery();  
27.                     int count = 0;  
28.                     if (rs.next()) {  
29.                         count = rs.getInt(1);  
30.                     }  
31.                     rs.close();  
32.                     countStmt.close();  
33.                     //System.out.println(count);  
34.                     Page page = null;  
35.                     if(parameterObject instanceof Page){    //参数就是Page实体  
36.                          page = (Page) parameterObject;  
37.                          page.setEntityOrField(true);    //见com.flf.entity.Page.entityOrField 注释  
38.                         page.setTotalResult(count);  
39.                     }else{  //参数为某个实体，该实体拥有Page属性  
40.                         Field pageField = ReflectHelper.getFieldByFieldName(parameterObject,"page");  
41.                         if(pageField!=null){  
42.                             page = (Page) ReflectHelper.getValueByFieldName(parameterObject,"page");  
43.                             if(page==null)  
44.                                 page = new Page();  
45.                             page.setEntityOrField(false); //见com.flf.entity.Page.entityOrField 注释  
46.                             page.setTotalResult(count);  
47.                             ReflectHelper.setValueByFieldName(parameterObject,"page", page); //通过反射，对实体对象设置分页对象  
48.                         }else{  
49.                             throw new NoSuchFieldException(parameterObject.getClass().getName()+"不存在 page 属性！");  
50.                         }  
51.                     }  
52.                     String pageSql = generatePageSql(sql,page);  
53.                     ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql); //将分页sql语句反射回BoundSql.  
54.                 }  
55.             }  
56.         }  
57.         return ivk.proceed();  
58.     }  
59.   
60.       
61.     /** 
62.      * 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler 
63.      * @param ps 
64.      * @param mappedStatement 
65.      * @param boundSql 
66.      * @param parameterObject 
67.      * @throws SQLException 
68.      */  
69.     private void setParameters(PreparedStatement ps,MappedStatement mappedStatement,BoundSql boundSql,Object parameterObject) throws SQLException {  
70.         ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());  
71.         List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();  
72.         if (parameterMappings != null) {  
73.             Configuration configuration = mappedStatement.getConfiguration();  
74.             TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();  
75.             MetaObject metaObject = parameterObject == null ? null: configuration.newMetaObject(parameterObject);  
76.             for (int i = 0; i < parameterMappings.size(); i++) {  
77.                 ParameterMapping parameterMapping = parameterMappings.get(i);  
78.                 if (parameterMapping.getMode() != ParameterMode.OUT) {  
79.                     Object value;  
80.                     String propertyName = parameterMapping.getProperty();  
81.                     PropertyTokenizer prop = new PropertyTokenizer(propertyName);  
82.                     if (parameterObject == null) {  
83.                         value = null;  
84.                     } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {  
85.                         value = parameterObject;  
86.                     } else if (boundSql.hasAdditionalParameter(propertyName)) {  
87.                         value = boundSql.getAdditionalParameter(propertyName);  
88.                     } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)&& boundSql.hasAdditionalParameter(prop.getName())) {  
89.                         value = boundSql.getAdditionalParameter(prop.getName());  
90.                         if (value != null) {  
91.                             value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));  
92.                         }  
93.                     } else {  
94.                         value = metaObject == null ? null : metaObject.getValue(propertyName);  
95.                     }  
96.                     TypeHandler typeHandler = parameterMapping.getTypeHandler();  
97.                     if (typeHandler == null) {  
98.                         throw new ExecutorException("There was no TypeHandler found for parameter "+ propertyName + " of statement "+ mappedStatement.getId());  
99.                     }  
100.                     typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());  
101.                 }  
102.             }  
103.         }  
104.     }  
105.       
106.     /** 
107.      * 根据数据库方言，生成特定的分页sql 
108.      * @param sql 
109.      * @param page 
110.      * @return 
111.      */  
112.     private String generatePageSql(String sql,Page page){  
113.         if(page!=null && Tools.notEmpty(dialect)){  
114.             StringBuffer pageSql = new StringBuffer();  
115.             if("mysql".equals(dialect)){  
116.                 pageSql.append(sql);  
117.                 pageSql.append(" limit "+page.getCurrentResult()+","+page.getShowCount());  
118.             }else if("oracle".equals(dialect)){  
119.                 pageSql.append("select * from (select tmp_tb.*,ROWNUM row_id from (");  
120.                 pageSql.append(sql);  
121.                 pageSql.append(") as tmp_tb where ROWNUM<=");  
122.                 pageSql.append(page.getCurrentResult()+page.getShowCount());  
123.                 pageSql.append(") where row_id>");  
124.                 pageSql.append(page.getCurrentResult());  
125.             }  
126.             return pageSql.toString();  
127.         }else{  
128.             return sql;  
129.         }  
130.     }  
131.       
132.     public Object plugin(Object arg0) {  
133.         // TODO Auto-generated method stub  
134.         return Plugin.wrap(arg0, this);  
135.     }  
136.   
137.     public void setProperties(Properties p) {  
138.         dialect = p.getProperty("dialect");  
139.         if (Tools.isEmpty(dialect)) {  
140.             try {  
141.                 throw new PropertyException("dialect property is not found!");  
142.             } catch (PropertyException e) {  
143.                 // TODO Auto-generated catch block  
144.                 e.printStackTrace();  
145.             }  
146.         }  
147.         pageSqlId = p.getProperty("pageSqlId");  
148.         if (Tools.isEmpty(pageSqlId)) {  
149.             try {  
150.                 throw new PropertyException("pageSqlId property is not found!");  
151.             } catch (PropertyException e) {  
152.                 // TODO Auto-generated catch block  
153.                 e.printStackTrace();  
154.             }  
155.         }  
156.     }  
157.       
158. }  

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：

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1. <plugins>  
2.     <plugin interceptor="com.flf.plugin.PagePlugin">  
3.         <property name="dialect" value="mysql"/>  
4.         <property name="pageSqlId" value=".*listPage.*"/>  
5.     </plugin>  
6. </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：

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1. /** 
2.  * @author Administrator 
3.  *  反射工具 
4.  */  
5. public class ReflectHelper {  
6.     /** 
7.      * 获取obj对象fieldName的Field 
8.      * @param obj 
9.      * @param fieldName 
10.      * @return 
11.      */  
12.     public static Field getFieldByFieldName(Object obj, String fieldName) {  
13.         for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass  
14.                 .getSuperclass()) {  
15.             try {  
16.                 return superClass.getDeclaredField(fieldName);  
17.             } catch (NoSuchFieldException e) {  
18.             }  
19.         }  
20.         return null;  
21.     }  
22.   
23.     /** 
24.      * 获取obj对象fieldName的属性值 
25.      * @param obj 
26.      * @param fieldName 
27.      * @return 
28.      * @throws SecurityException 
29.      * @throws NoSuchFieldException 
30.      * @throws IllegalArgumentException 
31.      * @throws IllegalAccessException 
32.      */  
33.     public static Object getValueByFieldName(Object obj, String fieldName)  
34.             throws SecurityException, NoSuchFieldException,  
35.             IllegalArgumentException, IllegalAccessException {  
36.         Field field = getFieldByFieldName(obj, fieldName);  
37.         Object value = null;  
38.         if(field!=null){  
39.             if (field.isAccessible()) {  
40.                 value = field.get(obj);  
41.             } else {  
42.                 field.setAccessible(true);  
43.                 value = field.get(obj);  
44.                 field.setAccessible(false);  
45.             }  
46.         }  
47.         return value;  
48.     }  
49.   
50.     /** 
51.      * 设置obj对象fieldName的属性值 
52.      * @param obj 
53.      * @param fieldName 
54.      * @param value 
55.      * @throws SecurityException 
56.      * @throws NoSuchFieldException 
57.      * @throws IllegalArgumentException 
58.      * @throws IllegalAccessException 
59.      */  
60.     public static void setValueByFieldName(Object obj, String fieldName,  
61.             Object value) throws SecurityException, NoSuchFieldException,  
62.             IllegalArgumentException, IllegalAccessException {  
63.         Field field = obj.getClass().getDeclaredField(fieldName);  
64.         if (field.isAccessible()) {  
65.             field.set(obj, value);  
66.         } else {  
67.             field.setAccessible(true);  
68.             field.set(obj, value);  
69.             field.setAccessible(false);  
70.         }  
71.     }  
72. }  

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。

具体参考例子见http://blog.csdn.net/fulinkster/article/details/6585157！

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