java读取文件内容再编辑
有时候，我们需要将读取文件的内容到一个byte[] 数组中，然后对这个数组进行一些修改，这时，我们可以借助于ByteArrayOutputStream 这个类来实现。
ByteArrayOutputStream，顾名思义，同样是一个OutputStream，那么，对于它的写入操作，和其他的 OutputStream应该是没有什么两样，写入代码可以说是随手拈来的，与其他输出流的不同之处在于，ByteArrayOutputStream写入到内存中，并提供一个 toByteArray() 方法返回我们所需要的byte[]。
//保存上传的附件信息String filename = files[0];String filepath = "upload/append/"+files[1];BufferedInputStream in = new BufferedInputStream(new FileInputStream(filepath));ByteArrayOutputStream out = new ByteArrayOutputStream(2048);System.out.println("available bytes"+in.available());byte[] temp = new byte[2048];int size =0;while((size = in.read(temp))!=-1){ out.write(temp,0,size);}in.close();byte[] content = out.toByteArray();String stream = new BaseCode64().EncodeBase64(content);System.out.println("content" +content.length); effect += insertAttachmentInfo(conn,attNo,processId,filename,stream);package com.ving.xzfw.util;import java.io.ByteArrayOutputStream;public class BaseCode64 {private String TableBase64;private String FError;public BaseCode64(){TableBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";FError = new String();FError = "";}public String DecodeBase64(byte [] Value){ByteArrayOutputStream o = new ByteArrayOutputStream();byte d[] = new byte[4];try{int count = 0;byte x[] = Value;do{if(count >= x.length){break;}for(int n = 0; n <= 3; n++){if(count >= x.length){d[n] = 64;} else{int y = TableBase64.indexOf(x[count]);if(y < 0){y = 65;}d[n] = (byte)y;}count++;}o.write((byte)(((d[0] & 0x3f) << 2) + ((d[1] & 0x30) >> 4)));if(d[2] != 64){o.write((byte)(((d[1] & 0xf) << 4) + ((d[2] & 0x3c) >> 2)));if(d[3] != 64){o.write((byte)(((d[2] & 3) << 6) + (d[3] & 0x3f)));}}} while(true);}catch(StringIndexOutOfBoundsException e){FError = String.valueOf(String.valueOf(FError)) + String.valueOf(String.valueOf(e.toString()));System.out.println(e.toString());}return o.toString();}public String EncodeBase64(byte [] Value){ByteArrayOutputStream o = new ByteArrayOutputStream();byte d[] = new byte[4];try{int count = 0;for(byte x[] = Value; count < x.length;){byte c = x[count];count++;d[0] = (byte)((c & 0xfc) >> 2);d[1] = (byte)((c & 3) << 4);if(count < x.length){c = x[count];count++;d[1] = (byte)(d[1] + (byte)((c & 0xf0) >> 4));d[2] = (byte)((c & 0xf) << 2);if(count < x.length){c = x[count];count++;d[2] = (byte)(d[2] + ((c & 0xc0) >> 6));d[3] = (byte)(c & 0x3f);} else{d[3] = 64;}} else{d[2] = 64;d[3] = 64;}int n = 0;while(n <= 3) {o.write(TableBase64.charAt(d[n]));n++;}}}catch(StringIndexOutOfBoundsException e){FError = String.valueOf(String.valueOf(FError)) + String.valueOf(String.valueOf(e.toString()));System.out.println(e.toString());}return o.toString();}}