Findbugs的OBL处理方法

最近在整代码的持续集成，findbugs进行代码的静态检查。其中一个findbugs警告解决了好久，先看示例代码：

private void copyDataBase() {
        InputStream myInput = null;
        OutputStream myOutput = null;
        try {
            String inFileName = "";//your local db path
            // Open your local db as the input stream
            myInput = new FileInputStream(inFileName);
            // Path to the just created empty db
            String outFileName = ""//the new db file u want to create;
            // Open the empty db as the output stream
            myOutput = new FileOutputStream(outFileName);
            // transfer bytes from the inputfile to the outputfile
            byte[] buffer = new byte[1024];
            int length;
            while ((length = myInput.read(buffer)) > 0) {
                myOutput.write(buffer, 0, length);
            }
            // Close the streams
            myOutput.flush();
            myOutput.close();
            myOutput = null;
            myInput.close();
            myInput = null;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if(myInput != null) {
                    myInput.close();
                }
                if(myOutput != null) {
                    myOutput.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            myInput = null;
            myOutput = null;
        }
    }

首先来看findbugs的警告：

OBL_UNSATISFIED_OBLIGATION, Priority: Normal

OBL: copyDataBase() may fail to clean up java.io.OutputStream

This method may fail to clean up (close, dispose of) a stream,
database object, or other resource requiring an explicit cleanup
operation.

In general, if a method opens a stream or other resource, the method
should use a try/finally block to ensure that the stream or resource
is cleaned up before the method returns.

This bug pattern is essentially the same as the **OS_OPEN_STREAM and
ODR_OPEN_DATABASE_RESOURCE** bug patterns, but is based on a different
(and hopefully better) static analysis technique. We are interested is
getting feedback about the usefulness of this bug pattern. To send
feedback, either: •send email to [email protected] •file a bug
report: http://findbugs.sourceforge.net/reportingBugs.html

In particular, the false-positive suppression heuristics for this bug
pattern have not been extensively tuned, so reports about false
positives are helpful to us.

See Weimer and Necula, Finding and Preventing Run-Time Error Handling
Mistakes, for a description of the analysis technique.

这里提示应该用try/finally来确保stream的clean up，但函数里也使用了finally，判断stream是否释放了，为什么还是报这样的警告呢？

然后再尝试在catch中也加入对stream的处理

 catch (IOException e) {
        e.printStackTrace();
        try {
            if(myInput != null) {
                myInput.close();
            }
            if(myOutput != null) {
                myOutput.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        myInput = null;
        myOutput = null;
    }

然并卵，还是报同样的警告。
最后仔细研究了findbugs的提示“use a try/finally block”，是不是这里不能使用catch了呢？就尝试在函数抛出异常到外部处理了

private void copyDataBase() throws IOException {
        InputStream myInput = null;
        OutputStream myOutput = null;
        try {
            String inFileName = "";//your local db path
            // Open your local db as the input stream
            myInput = new FileInputStream(inFileName);
            // Path to the just created empty db
            String outFileName = ""//the new db file u want to create;
            // Open the empty db as the output stream
            myOutput = new FileOutputStream(outFileName);
            // transfer bytes from the inputfile to the outputfile
            byte[] buffer = new byte[1024];
            int length;
            while ((length = myInput.read(buffer)) > 0) {
                myOutput.write(buffer, 0, length);
            }
            // Close the streams
            myOutput.flush();
            myOutput.close();
            myOutput = null;
            myInput.close();
            myInput = null;
        } finally {
            try {
                if(myInput != null) {
                    myInput.close();
                }
                if(myOutput != null) {
                    myOutput.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            myInput = null;
            myOutput = null;
        }
    }

重新findbugs检查下，发现不再报警告了。
可能findbugs的检查机制是只能在finally中处理stream的异常吧，所以这里不能出现catch，异常抛出外部处理当然就检查不到了。
但是findbugs这里也提了，这个警告可能也不需要调整修改，可能是错误的建议，可以反馈给findbugs。

In particular, the false-positive suppression heuristics for this bug
pattern have not been extensively tuned, so reports about false
positives are helpful to us.

这里仅分享下此findbugs警告的修改方法，不强制说一定要修改此警告。

转载请声明原文地址：
http://blog.csdn.net/sagittarius1988/article/details/49795795