有如下代码:
private static String extractContent(HttpResponse response) throws Exception {
String htmStr = null;
if (response.getStatusLine().getStatusCode() == 200) {
if (response != null) {
BufferedReader br = null;
InputStream ins = null;
try {
HttpEntity entity = response.getEntity();
ins = entity.getContent();
br = new BufferedReader(new InputStreamReader(ins, "UTF-8"));
StringBuffer sbf = new StringBuffer();
String line = null;
while ((line = br.readLine()) != null) {
sbf.append(line);
}
// 处理内容
htmStr = sbf.toString();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != br) {
br.close();
}
if (null != ins) {
ins.close();
}
}
}
}
return htmStr;
}
代码中的br 和ins都正确的关闭掉了。但是在使用InputStreamReader的时候,是通过
br = new BufferedReader(new InputStreamReader(ins, "UTF-8"));
来使用的,那么InputStreamReader是否需要显示的关闭,即改成:
private static String extractContent(HttpResponse response) throws Exception {
String htmStr = null;
if (response.getStatusLine().getStatusCode() == 200) {
if (response != null) {
BufferedReader br = null;
InputStream ins = null;
InputStreamReader inr = null;
try {
HttpEntity entity = response.getEntity();
ins = entity.getContent();
inr = new InputStreamReader(ins, "UTF-8");
br = new BufferedReader(inr);
StringBuffer sbf = new StringBuffer();
String line = null;
while ((line = br.readLine()) != null) {
sbf.append(line);
}
// 处理内容
htmStr = sbf.toString();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != br) {
br.close();
}
if (null != ins) {
ins.close();
}
if (null != inr) {
inr.close();
}
}
}
}
return htmStr;
}
我知道在JDK7之后提供了try with resources的方法解决了这种问题,但是在JDK7之前是不是必须的这样用,显示的分别new相应流对象,然后最后再关闭,而不能
br = new BufferedReader(new InputStreamReader(ins, "UTF-8"));
像这样嵌套这来用。
我的问题:
1.如果没有流关闭,会带来安全隐患,具体带来何种安全隐患?最好能举例说明。还有说没有正确的关闭流,会造成系统资源的浪费,具体是指什么?(我的理解是浪费CPU资源,导致CPU轮询去查询是否有I/O传输,这样的理解对不对啊)??
2.jdk1.7之前,流的使用,是不是必须要用这种结构:
BufferedReader ins = null;
InputStreamReader inr = null;
try{
ins = ...
inr = ...
}catch{
...
}finally{
if(null != ins) ins.close;
if(null != inr) inr.close;
}
而不能使用这样的结构:
BufferedReader ins = null;
try{
ins = new InputStreamReader(new InputStrea(System.in, "UTF-8"));
}catch{
...
}finally{
if(null != ins) ins.close;
}
https://segmentfault.com/q/1010000005970993?_ea=969143