本人用StringReader读取一个字符串,字符串长度为1100000以上,是一段标签。结果读取后长度小于原字符串长度(后面的部分被截掉了),请各位大侠支支招!小男子无以为报,愿以分相许!哈哈!
注:可以考虑用其它方法,但必须将这个字符串放到一个Reader(如FileReader)里。
注:可以考虑用其它方法,但必须将这个字符串放到一个Reader(如FileReader)里。
解决方案 »
- struts2 select标签默认值问题
- 学生管理系统怎么做呢?小弟请各位大侠帮忙
- Struts 1.x 中。最好的分页插件是什么?
- Servlet超基础PrintWriter ??
- 100分求助,一个项目的数据存储方案,求经验大神指导
- 项目合作+给个意见看看怎么报价+怎么合作!!!!
- 我在做.NET项目而我想同时学JAVA应该怎么学那些东西才能一举两得!
- tomcat5+weblogic8的问题
- JBuilder8.0 + WebLogic7.0 + SQLServer2000
- 关于日志记录,用spring aop还是在每个方法中逐次进行记录?
- 遍历Map
- ejb现在是怎么个情况?还有发展吗?
是否是读取这个标签再写到另一个文件中,还是读取这个标签使用。
第一种字节流可以,第二种BufferReader的readLine应该可以。
看如下实例:public static void main(String[] args) throws IOException {
FileWriter fileWriter = new FileWriter(new File("c:/test.txt"));
BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
for (int i = 0; i < 10000000; i++) {
bufferedWriter.write("12345678901234567890");
}
bufferedWriter.flush();
bufferedWriter.close();
FileReader fileReader = new FileReader(new File("c:/test.txt"));
BufferedReader bufferedReader = new BufferedReader(fileReader);
bufferedReader.skip(1000000l); //跳过长度-字节
char[] bs = new char[1];
bufferedReader.read(bs);
System.out.println(bs[0]);
}API:http://www.gznc.edu.cn/yxsz/jjglxy/book/Java_api/java/io/BufferedReader.html
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ request.setCharacterEncoding("utf-8");//注意编码 String type = request.getParameter("type"); String svg = request.getParameter("svg");//就是要读取这个字符串,稍短时没有问题 response.setCharacterEncoding("utf-8"); ServletOutputStream out = response.getOutputStream(); if (null != type && null != svg){ svg = svg.replaceAll(":rect", "rect"); String ext = ""; Transcoder t = null; if (type.equals("image/png")) { ext = "png"; t = new PNGTranscoder(); } else if (type.equals("image/jpeg")) { ext = "jpg"; t = new JPEGTranscoder(); } else if (type.equals("application/pdf")) { ext = "pdf"; t = new PDFTranscoder(); } else if (type.equals("image/svg+xml")) { ext = "svg"; } response.addHeader("Content-Disposition", "attachment; filename=chart."+ext); response.addHeader("Content-Type", type); if (null != t){ StringReader sr = new StringReader(svg); //问题出在这儿,由于svg太长而被截取
TranscoderInput input = new TranscoderInput(sr); TranscoderOutput output = new TranscoderOutput(out); try { t.transcode(input,output);//在此处抛出了异常
} catch (TranscoderException e){ out.print("编码流错误."); e.printStackTrace(); } } else if (ext == "svg"){ svg = svg.replace("http://www.w3.org/2000/svg", "http://www.w3.org/TR/SVG11/"); out.print(svg); } else { out.print("Invalid type: " + type); } } else { response.addHeader("Content-Type", "text/html"); } out.flush(); out.close(); } }
Transcoder svg的处理。。没有做过。。不能确定能不能分段处理。。不过LZ可以试试:
String svg = request.getParameter("svg");
传过来的svg参数,在传递的时候可以检查固定长度。。然后分段传递一个数组类型的过来,,程序接收数组类型的多段字符串片段StringReader sr = new StringReader(svg);
TranscoderInput input = new TranscoderInput(sr);
这里在循环将每个片段包装。。
t.transcode(input,output); // 这里看能否将所有片段组合进去。。
想办法确认一下这里被截取是不是因为jvm内存不足引起,比如用java.lang.Runtime类的一些方法
* Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/package java.io;
/**
* A character stream whose source is a string.
*
* @author Mark Reinhold
* @since JDK1.1
*/public class StringReader extends Reader { private String str;
private int length;
private int next = 0;
private int = 0; /**
* Creates a new string reader.
*
* @param s String providing the character stream.
*/
public StringReader(String s) {
this.str = s;
this.length = s.length();
} /** Check to make sure that the stream has not been closed */
private void ensureOpen() throws IOException {
if (str == null)
throw new IOException("Stream closed");
} /**
* Reads a single character.
*
* @return The character read, or -1 if the end of the stream has been
* reached
*
* @exception IOException If an I/O error occurs
*/
public int read() throws IOException {
synchronized (lock) {
ensureOpen();
if (next >= length)
return -1;
return str.charAt(next++);
}
} /**
* Reads characters into a portion of an array.
*
* @param cbuf Destination buffer
* @param off Offset at which to start writing characters
* @param len Maximum number of characters to read
*
* @return The number of characters read, or -1 if the end of the
* stream has been reached
*
* @exception IOException If an I/O error occurs
*/
public int read(char cbuf[], int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
((off + len) > cbuf.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}
if (next >= length)
return -1;
int n = Math.min(length - next, len);
str.getChars(next, next + n, cbuf, off);
next += n;
return n;
}
} /**
* Skips the specified number of characters in the stream. Returns
* the number of characters that were skipped.
*
* <p>The <code>ns</code> parameter may be negative, even though the
* <code>skip</code> method of the {@link Reader} superclass throws
* an exception in this case. Negative values of <code>ns</code> cause the
* stream to skip backwards. Negative return values indicate a skip
* backwards. It is not possible to skip backwards past the beginning of
* the string.
*
* <p>If the entire string has been read or skipped, then this method has
* no effect and always returns 0.
*
* @exception IOException If an I/O error occurs
*/
public long skip(long ns) throws IOException {
synchronized (lock) {
ensureOpen();
if (next >= length)
return 0;
// Bound skip by beginning and end of the source
long n = Math.min(length - next, ns);
n = Math.max(-next, n);
next += n;
return n;
}
} /**
* Tells whether this stream is ready to be read.
*
* @return True if the next read() is guaranteed not to block for input
*
* @exception IOException If the stream is closed
*/
public boolean ready() throws IOException {
synchronized (lock) {
ensureOpen();
return true;
}
} /**
* Tells whether this stream supports the () operation, which it does.
*/
public boolean Supported() {
return true;
} /**
* Marks the present position in the stream. Subsequent calls to reset()
* will reposition the stream to this point.
*
* @param readAheadLimit Limit on the number of characters that may be
* read while still preserving the . Because
* the stream's input comes from a string, there
* is no actual limit, so this argument must not
* be negative, but is otherwise ignored.
*
* @exception IllegalArgumentException If readAheadLimit is < 0
* @exception IOException If an I/O error occurs
*/
public void (int readAheadLimit) throws IOException {
if (readAheadLimit < 0){
throw new IllegalArgumentException("Read-ahead limit < 0");
}
synchronized (lock) {
ensureOpen();
= next;
}
} /**
* Resets the stream to the most recent , or to the beginning of the
* string if it has never been ed.
*
* @exception IOException If an I/O error occurs
*/
public void reset() throws IOException {
synchronized (lock) {
ensureOpen();
next = ;
}
} /**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(),
* ready(), (), or reset() invocations will throw an IOException.
* Closing a previously closed stream has no effect.
*/
public void close() {
str = null;
}
}
这里并没有排除内存不足的可能性
这行代码之前打印svg.length()确认svg长度,
之后使用int i=0;
while (sr.read()!=-1) {
i++;
}打印i确认sr中包含字符串的长度。
2.如果确认以上两个长度不相等,那就是StringReader类的bug了……这种java已建立多年的类,这样的概率有多大?经本人测试,jvm的Xmx=1024m下,字符串长度1000000000,StringReader并不会截断。
3.如果相等,那要么是jvm内存问题,可调整jvm尝试,要么是楼主自己的类的内部转换问题。
1100000长度不大可能内存不足,即使jvm内存不足,也不会截断,直接溢出了