原来采用
RS直接返回结果集进行计数5000行写入文件,每次都出现java heap space
对tomcat的catalina.bat文件加入
JAVA_OPTS=-Xmx512M
后生成文件效率提高,但生成20左右文件时还是会出现java heap space
后采用rownum分页
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//////这儿进行分指定行生成xml文件
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int ipage=xmlfilenum; //分页单位
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int allpage=0; //总页数
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//int pages=0; //接受的页码变量
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int cpage=1; //当前页
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//int spage=0; //开始页
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int allCol=0;
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//Vector v=null;
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String sql,pagesql,ssql2;
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ssql2=FileName;
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// 取总文章数
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pagesql = "SELECT COUNT(*) FROM "+ssql2;
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//statement = conn.createStatement();
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rs=excuteQuery(pagesql);
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//pagers = statement.executeQuery(pagesql);
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while(rs.next())
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{
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allCol = rs.getInt(1);
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System.out.println("###############总行数############<BR>");
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System.out.println(allCol);
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System.out.println("###########################<BR>");
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}
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//获得总页面数
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allpage = (int)Math.ceil((allCol + ipage-1) / ipage);
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for(cpage=1;cpage<=allpage;cpage++)
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{
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sql="select * from (select rownum no,t.* from "+ssql2 +" t where rownum<"+cpage*ipage+") where no>"+(cpage-1)*ipage;
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t_FileNameCount=cpage;
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DataOutputStream t_Output=null;
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t_FileName = "";
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t_FileName = fTmpXmlPreDir + "\\" + FileName + "Xml\\" + FileName + "_" + t_FileNameCount + "_" + "Xml.xml";
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fTmpXmlFileName.add(t_FileName);//存储文件名包括路径
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//fTmpXmlFileName2.add(FileName + "Xml/" + FileName + "_" + t_FileNameCount + "_" + "Xml.xml");//存储文件名不包括路径
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t_Output = new DataOutputStream (new BufferedOutputStream(new FileOutputStream(t_FileName)));
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t_Output.write(t_PreData.getBytes("UTF8"));
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//先在文件中将xml文档的所有头部描述 部分写入
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rs=excuteQuery(sql);
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while(rs.next())
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{
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String t_aRowData = "";
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for( int i1=0 ; i1 < this.columnNames.length ; ++i1)
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{
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if (rs.getString(i1+2)!=null)//+2 跳过分页时的no字段
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{
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t_aRowData = t_aRowData + " Col" + i1 + "=\"" + rs.getString(i1+2) + "\"";
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}
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}
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//t_RowData = t_RowData + "<z:row "+ t_aRowData + " />\n";
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t_aRowData = "<z:row "+ t_aRowData + " />\n";
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t_Output.write(t_aRowData.getBytes("UTF8"));
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}
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String t_WriteData = " </rs:data>\n </x:PivotCache>\n</xml>\n";
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t_Output.write(t_WriteData.getBytes("UTF8"));
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t_Output.close();//每2000行关闭文件,重新创新新文件做准备
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System.gc();
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} //end for allpage

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终于搞定.细节再调整中