使用FileInputStream讀取xml文件

Question

我正在閱讀使用下面給出的代碼的XML文件，但每當我讀取XML並打印相同時，XML的開始標記始終缺失，從而產生錯誤。

代碼讀取XML：

package com.vaannila.action; 

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileReader; 

import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 

import org.apache.struts.action.Action; 
import org.apache.struts.action.ActionForm; 
import org.apache.struts.action.ActionForward; 
import org.apache.struts.action.ActionMapping; 

import com.vaannila.FormBean.XmlRetrivalForm; 

public class AppletRefeshAction extends Action { 
    String filepath = "C:/Users/ashutosh_k/idoc/docRuleTool/WebContent/data/Malaria.xml"; 
    @Override 
    public ActionForward execute(ActionMapping mapping, ActionForm form, 
      HttpServletRequest request, HttpServletResponse response) 
      throws Exception { 
     XmlRetrivalForm xrf = (XmlRetrivalForm)form; 
     String dieasename =xrf.getDieseasename(); 
     System.out.println("ghhjhhjkh"+dieasename); 
     /* this part of the code is from jsp */ 
     //FileReader fis = new FileReader(new File(filepath)); 
     FileInputStream fis = new FileInputStream(new File(filepath)); 
     byte bin[] = new byte[(int) new File(filepath).length()]; 
     while(fis.read()>0){ 
     fis.read(bin); 
     } 
     System.out.println("I am here after reading the xml part of it "); 
     response.setContentType("text/xml"); 
     response.setCharacterEncoding("UTF-8"); 
     response.getOutputStream().write(bin); 
//  response.getWriter().write(bin); 
     String ashu = new String(bin); 
     String iam =ashu.trim(); 
     System.out.println("i am in the new action class now "); 
     System.out.println(iam); 
     fis.close(); 
     /* this part of the code jsp ends here */ 
     return null; 
    } 

} 

輸出XML生成：

?xml version="1.0" encoding="UTF-8" standalone="no"?><tree> 
<declarations> 
    <attributeDecl name="name" type="String"/> 
</declarations> 
<branch> 
<branch> 
<attribute name="name" value="Excess Stool"/> 
<branch> 
<branch> 
<attribute name="name" value="Do you have this condition for more than a weeks time"/> 
<branch> 
<attribute name="name" value=""/></branch> 
<branch> 
<attribute name="name" value=""/></branch> 
</branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
<attribute name="name" value="Do you have watery stool"/></branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
</branch> 
<branch> 
<branch> 
<attribute name="name" value="Was your peak temperature greater than 104"/> 
<branch> 
<branch> 
<attribute name="name" value="Do you have chills"/> 
</branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
<attribute name="name" value="Do you have high fever for more than a weeks time "/></branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
</branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
<attribute name="name" value="High Fever"/></branch> 
<branch> 
<branch> 
<attribute name="name" value="Do you have pain in the left part of the head "/> 
<branch> 
<branch> 
<attribute name="name" value="Duration of the headache spans for more than a day "/> 
</branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
<attribute name="name" value="Do you have headache more than 5 times a day "/></branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
</branch> 
<branch> 
<attribute name="name" value="No"/></branch> 
<attribute name="name" value="Bodyache"/></branch> 
<attribute name="name" value="Malaria"/></branch> 
</tree> 

Answer 1

首先，您正在讀入每個循環迭代中相同偏移量的字節緩衝區 - 您不能指望一次總是讀取整個文件。其次，不要在字節流和字符流之間進行不必要的轉換 - 您應該將XML讀取爲字節並將其「轉發」爲字節。要小心如何在字節數組和字符串之間進行轉換 - 請記住，新的String(byte[])使用平臺默認字符編碼（可能不是utf-8）將字節轉換爲字符。

// read the file 
ByteArrayOutputStream out = new ByteArrayOutputStream(10000); 
InputStream in = new BufferedInputStream(new FileInputStream(filepath)); 
int c; 
while ((c = in.read()) != -1) 
    out.write(c); 
in.close(); 

// debug as string 
if (debug) { 
    System.out.writeln(new String(out.toBytes(), Charset.forName("utf-8")); 
} 


// forward to client through response 
response.setContentType("text/xml"); 
response.setCharacterEncoding("UTF-8"); 
response.getOutputStream().write(out.toBytes()); 

Answer 2

爲什麼呢？

FileInputStream fis = new FileInputStream(new File(filepath)); 
    byte bin[] = new byte[(int) new File(filepath).length()]; 
    while(fis.read()>0){ 
    fis.read(bin); 
    } 

而不是這個來讀取文本？

BufferedReader reader = new BufferedReader(new FileReader(filepath)); 
String line = null; 
StringBuilder builder = new StringBuilder(); 
while ((line = reader.readLine()) != null) 
    builder.append(line); 
reader.close();