读取Java文件到byte数组的三种方式

2013-11-22 13:35 18856人阅读 评论(0)收藏举报

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1. package zs;  
2.   
3. import java.io.BufferedInputStream;  
4. import java.io.ByteArrayOutputStream;  
5. import java.io.File;  
6. import java.io.FileInputStream;  
7. import java.io.FileNotFoundException;  
8. import java.io.IOException;  
9. import java.io.RandomAccessFile;  
10. import java.nio.ByteBuffer;  
11. import java.nio.MappedByteBuffer;  
12. import java.nio.channels.FileChannel;  
13. import java.nio.channels.FileChannel.MapMode;  
14.   
15. public class FileUtils {  
16.     public byte[] getContent(String filePath) throws IOException {  
17.         File file = new File(filePath);  
18.         long fileSize = file.length();  
19.         if (fileSize > Integer.MAX_VALUE) {  
20.             System.out.println("file too big...");  
21.             return null;  
22.         }  
23.         FileInputStream fi = new FileInputStream(file);  
24.         byte[] buffer = new byte[(int) fileSize];  
25.         int offset = 0;  
26.         int numRead = 0;  
27.         while (offset < buffer.length  
28.         && (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {  
29.             offset += numRead;  
30.         }  
31.         // 确保所有数据均被读取  
32.         if (offset != buffer.length) {  
33.         throw new IOException("Could not completely read file "  
34.                     + file.getName());  
35.         }  
36.         fi.close();  
37.         return buffer;  
38.     }  
39.   
40.     /** 
41.      * the traditional io way 
42.      *  
43.      * @param filename 
44.      * @return 
45.      * @throws IOException 
46.      */  
47.     public static byte[] toByteArray(String filename) throws IOException {  
48.   
49.         File f = new File(filename);  
50.         if (!f.exists()) {  
51.             throw new FileNotFoundException(filename);  
52.         }  
53.   
54.         ByteArrayOutputStream bos = new ByteArrayOutputStream((int) f.length());  
55.         BufferedInputStream in = null;  
56.         try {  
57.             in = new BufferedInputStream(new FileInputStream(f));  
58.             int buf_size = 1024;  
59.             byte[] buffer = new byte[buf_size];  
60.             int len = 0;  
61.             while (-1 != (len = in.read(buffer, 0, buf_size))) {  
62.                 bos.write(buffer, 0, len);  
63.             }  
64.             return bos.toByteArray();  
65.         } catch (IOException e) {  
66.             e.printStackTrace();  
67.             throw e;  
68.         } finally {  
69.             try {  
70.                 in.close();  
71.             } catch (IOException e) {  
72.                 e.printStackTrace();  
73.             }  
74.             bos.close();  
75.         }  
76.     }  
77.   
78.     /** 
79.      * NIO way 
80.      *  
81.      * @param filename 
82.      * @return 
83.      * @throws IOException 
84.      */  
85.     public static byte[] toByteArray2(String filename) throws IOException {  
86.   
87.         File f = new File(filename);  
88.         if (!f.exists()) {  
89.             throw new FileNotFoundException(filename);  
90.         }  
91.   
92.         FileChannel channel = null;  
93.         FileInputStream fs = null;  
94.         try {  
95.             fs = new FileInputStream(f);  
96.             channel = fs.getChannel();  
97.             ByteBuffer byteBuffer = ByteBuffer.allocate((int) channel.size());  
98.             while ((channel.read(byteBuffer)) > 0) {  
99.                 // do nothing  
100.                 // System.out.println("reading");  
101.             }  
102.             return byteBuffer.array();  
103.         } catch (IOException e) {  
104.             e.printStackTrace();  
105.             throw e;  
106.         } finally {  
107.             try {  
108.                 channel.close();  
109.             } catch (IOException e) {  
110.                 e.printStackTrace();  
111.             }  
112.             try {  
113.                 fs.close();  
114.             } catch (IOException e) {  
115.                 e.printStackTrace();  
116.             }  
117.         }  
118.     }  
119.   
120.     /** 
121.      * Mapped File way MappedByteBuffer 可以在处理大文件时，提升性能 
122.      *  
123.      * @param filename 
124.      * @return 
125.      * @throws IOException 
126.      */  
127.     public static byte[] toByteArray3(String filename) throws IOException {  
128.   
129.         FileChannel fc = null;  
130.         try {  
131.             fc = new RandomAccessFile(filename, "r").getChannel();  
132.             MappedByteBuffer byteBuffer = fc.map(MapMode.READ_ONLY, 0,  
133.                     fc.size()).load();  
134.             System.out.println(byteBuffer.isLoaded());  
135.             byte[] result = new byte[(int) fc.size()];  
136.             if (byteBuffer.remaining() > 0) {  
137.                 // System.out.println("remain");  
138.                 byteBuffer.get(result, 0, byteBuffer.remaining());  
139.             }  
140.             return result;  
141.         } catch (IOException e) {  
142.             e.printStackTrace();  
143.             throw e;  
144.         } finally {  
145.             try {  
146.                 fc.close();  
147.             } catch (IOException e) {  
148.                 e.printStackTrace();  
149.             }  
150.         }  
151.     }  
152. }  

package zs;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.RandomAccessFile;import java.nio.ByteBuffer;import java.nio.MappedByteBuffer;import java.nio.channels.FileChannel;import java.nio.channels.FileChannel.MapMode;public class FileUtils {public byte[] getContent(String filePath) throws IOException {File file = new File(filePath);long fileSize = file.length();if (fileSize > Integer.MAX_VALUE) {System.out.println("file too big...");return null;}FileInputStream fi = new FileInputStream(file);byte[] buffer = new byte[(int) fileSize];int offset = 0;int numRead = 0;while (offset < buffer.length&& (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {offset += numRead;}// 确保所有数据均被读取if (offset != buffer.length) {throw new IOException("Could not completely read file "+ file.getName());}fi.close();return buffer;}/** * the traditional io way *  * @param filename * @return * @throws IOException */public static byte[] toByteArray(String filename) throws IOException {File f = new File(filename);if (!f.exists()) {throw new FileNotFoundException(filename);}ByteArrayOutputStream bos = new ByteArrayOutputStream((int) f.length());BufferedInputStream in = null;try {in = new BufferedInputStream(new FileInputStream(f));int buf_size = 1024;byte[] buffer = new byte[buf_size];int len = 0;while (-1 != (len = in.read(buffer, 0, buf_size))) {bos.write(buffer, 0, len);}return bos.toByteArray();} catch (IOException e) {e.printStackTrace();throw e;} finally {try {in.close();} catch (IOException e) {e.printStackTrace();}bos.close();}}/** * NIO way *  * @param filename * @return * @throws IOException */public static byte[] toByteArray2(String filename) throws IOException {File f = new File(filename);if (!f.exists()) {throw new FileNotFoundException(filename);}FileChannel channel = null;FileInputStream fs = null;try {fs = new FileInputStream(f);channel = fs.getChannel();ByteBuffer byteBuffer = ByteBuffer.allocate((int) channel.size());while ((channel.read(byteBuffer)) > 0) {// do nothing// System.out.println("reading");}return byteBuffer.array();} catch (IOException e) {e.printStackTrace();throw e;} finally {try {channel.close();} catch (IOException e) {e.printStackTrace();}try {fs.close();} catch (IOException e) {e.printStackTrace();}}}/** * Mapped File way MappedByteBuffer 可以在处理大文件时，提升性能 *  * @param filename * @return * @throws IOException */public static byte[] toByteArray3(String filename) throws IOException {FileChannel fc = null;try {fc = new RandomAccessFile(filename, "r").getChannel();MappedByteBuffer byteBuffer = fc.map(MapMode.READ_ONLY, 0,fc.size()).load();System.out.println(byteBuffer.isLoaded());byte[] result = new byte[(int) fc.size()];if (byteBuffer.remaining() > 0) {// System.out.println("remain");byteBuffer.get(result, 0, byteBuffer.remaining());}return result;} catch (IOException e) {e.printStackTrace();throw e;} finally {try {fc.close();} catch (IOException e) {e.printStackTrace();}}}}

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