package com.lanyuan.pulgin.mybatis.plugin;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.Map.Entry;
import javax.xml.bind.PropertyException;
import org.apache.ibatis.executor.parameter.DefaultParameterHandler;
import org.apache.ibatis.executor.statement.BaseStatementHandler;
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.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 com.lanyuan.pulgin.jdbc.dialet.Dialect;
import com.lanyuan.util.Common;
import com.lanyuan.util.PageView;
/**
* Mybatis的分页查询插件，通过拦截StatementHandler的prepare方法来实现。
* 只有在参数列表中包括Page类型的参数时才进行分页查询。
* 在多参数的情况下，只对第一个Page类型的参数生效。
* 另外，在参数列表中，Page类型的参数无需用@Param来标注
* @author lanyuan
* 2013-11-19
* @Email: mmm333zzz520@163.com
* @version 1.0v
*/
@SuppressWarnings("unchecked")
@Intercepts( { @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
public class PagePlugin implements Interceptor {
private static Dialect dialectObject = null; // 数据库方言
private static String pageSqlId = ""; // mybaits的数据库xml映射文件中需要拦截的ID(正则匹配)
public Object intercept(Invocation ivk) throws Throwable {
if (ivk.getTarget() instanceof RoutingStatementHandler) {
RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk
.getTarget();
BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper
.getValueByFieldName(statementHandler, "delegate");
MappedStatement mappedStatement = (MappedStatement) ReflectHelper
.getValueByFieldName(delegate, "mappedStatement");
/**
* 方法1：通过ＩＤ来区分是否需要分页．.*query.*
* 方法2：传入的参数是否有page参数，如果有，则分页，
*/
// 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("boundSql.getParameterObject() is null!");
return ivk.proceed();
} else {
PageView pageView = null;
if (parameterObject instanceof PageView) { // 参数就是Pages实体
pageView = (PageView) parameterObject;
} else if (parameterObject instanceof Map) {
for (Entry entry : (Set<Entry>) ((Map) parameterObject)
.entrySet()) {
if (entry.getValue() instanceof PageView) {
pageView = (PageView) entry.getValue();
break;
}
}
} else { // 参数为某个实体，该实体拥有Pages属性
pageView = ReflectHelper.getValueByFieldType(
parameterObject, PageView.class);
if (pageView == null) {
return ivk.proceed();
}
}
String sql = boundSql.getSql();
PreparedStatement countStmt = null;
ResultSet rs = null;
try {
Connection connection = (Connection) ivk.getArgs()[0];
String countSql = "select count(1) from (" + sql
+ ") tmp_count"; // 记录统计
countStmt = connection.prepareStatement(countSql);
ReflectHelper.setValueByFieldName(boundSql, "sql",
countSql);
DefaultParameterHandler parameterHandler = new DefaultParameterHandler(
mappedStatement, parameterObject, boundSql);
parameterHandler.setParameters(countStmt);
rs = countStmt.executeQuery();
int count = 0;
if (rs.next()) {
count = ((Number) rs.getObject(1)).intValue();
}
pageView.setRowCount(count);
} finally {
try {
rs.close();
} catch (Exception e) {
}
try {
countStmt.close();
} catch (Exception e) {
}
}
String pageSql = generatePagesSql(sql, pageView);
ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql); // 将分页sql语句反射回BoundSql.
}
//}
}
return ivk.proceed();
}
/**
* 根据数据库方言，生成特定的分页sql
*
* @param sql
* @param page
* @return
*/
private String generatePagesSql(String sql, PageView page) {
if (page != null && dialectObject != null) {
//pageNow默认是从1，而已数据库是从0开始计算的．所以(page.getPageNow()-1)
int pageNow = page.getPageNow();
return dialectObject.getLimitString(sql, (pageNow<=0?0:pageNow-1)
* page.getPageSize(), page.getPageSize());
}
return sql;
}
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
public void setProperties(Properties p) {
String dialect = ""; // 数据库方言
dialect = p.getProperty("dialect");
if (Common.isEmpty(dialect)) {
try {
throw new PropertyException("dialect property is not found!");
} catch (PropertyException e) {
e.printStackTrace();
}
} else {
try {
dialectObject = (Dialect) Class.forName(dialect)
.getDeclaredConstructor().newInstance();
} catch (Exception e) {
throw new RuntimeException(dialect + ", init fail!\n" + e);
}
}
pageSqlId = p.getProperty("pageSqlId");//根据id来区分是否需要分页
if (Common.isEmpty(pageSqlId)) {
try {
throw new PropertyException("pageSqlId property is not found!");
} catch (PropertyException e) {
e.printStackTrace();
}
}
}
}