java.io.EOFException: Unexpected end of ZLIB input stream异常处理

java.io.EOFException: Unexpected end of ZLIB input stream异常处理

因需要完成压缩与解压缩功能，所以使用到java.util.zip中的类。同时使用了jdk 1.7 try with resource 的特性，结果暴出java.io.EOFException: Unexpected end of ZLIB input stream异常。

java.io.EOFException: Unexpected end of ZLIB input stream
    at java.util.zip.InflaterInputStream.fill(InflaterInputStream.java:240)
    at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:158)
    at java.util.zip.GZIPInputStream.read(GZIPInputStream.java:117)
    at java.io.FilterInputStream.read(FilterInputStream.java:107)
    at com.sf.framework.rpc.util.NioUtils.unzip(NioUtils.java:27)
    at framework.rpc.util.NioUtilsTest.unzipTest(NioUtilsTest.java:24)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

代码如下：

public class NioUtils {
    public static byte[] zip(byte[] bytes) {
        if (bytes != null && bytes.length > 0) {
            ByteArrayOutputStream byteOs = new ByteArrayOutputStream();
            try(GZIPOutputStream gZipOs = new GZIPOutputStream(byteOs)) {
                gZipOs.write(bytes);
                return byteOs.toByteArray();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return new byte[0];
    }

    public static byte[] unzip(byte[] bytes){
        try (GZIPInputStream gZipIs = new GZIPInputStream (new ByteArrayInputStream(bytes));
             ByteArrayOutputStream bos = new ByteArrayOutputStream()){
            byte[] buff = new byte[512];
            int read = gZipIs.read(buff);
            while(read > 0){
                bos.write(buff,0,read);
                read = gZipIs.read(buff);
            }
            return bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new byte[0];
    }
}

    @Test
    public void unzipTest(){
//      NioUtils.closeTest();
        byte[] bytes = str.getBytes();
        byte[] ziped = NioUtils.zip(bytes);
        byte[] unziped = NioUtils.unzip(ziped);
        String unZipedStr = new String(unziped);
        Assert.assertTrue(str.equals(unZipedStr));
    }

原本是想里用try-with-resource完成自动close，结果在解压缩获取到的压缩数据时出现异常。随后看了GZIPOutputStream 的源码，原来调用close的时候会填充一些压缩信息，这样才能在解压缩时正常解压缩。而上面的代码，bos.toByteArray();是在bos.close()调用前被调用，因此返回了不正确的字节数组，造成解压缩失败。

下面是执行try-with-resource执行顺序的一个测试。

public class NioUtils {
    public static T1 closeTest(){
        try(T t = new T()){
            return new T1();
        }
        catch(Exception e){
            e.printStackTrace();

        }
        return null;
    }
}

class T implements AutoCloseable{

    @Override
    public void close() throws Exception {
        System.out.println("AutoCloseable");
    }

}

class T1{
    T1(){
        System.out.println("a class for test.");
    }
}
输出：
a class for test.
AutoCloseable

可以看到close是在return 中new T()调用完后执行。

最后保证在对于解压缩，保证在压缩返回字节数组前close方法被调用即可解决出现的异常。