Android: setRequestProperty function of URLConnection, what does this method do?

问题

Although I know that StackOverflow has already setRequestProperty function of HttpURLConnection question, I really don't understand what this method does. I cannot "step into" it (F7) when debugging. I pressed Ctrl-B to view the method's body, but it only has the following code:

public void setRequestProperty(String field, String newValue) {
        checkNotConnected();
        if (field == null) {
            throw new NullPointerException("field == null");
        }
    }

and checkNotConnected:

private void checkNotConnected() {
        if (connected) {
            throw new IllegalStateException("Already connected");
        }
    }

I mean that where is the code that puts the value to the field? Any explanation is appreciated.

UPDATE (2015/08/08): I have found the way to view its implementation. Since it's abstract, must use Ctrl-Alt-B instead of Ctrl-B to view.

回答1:

I guess you are accessing the wrong way, or have some kind of protected code...

The original function is this:

/**
 * Sets the general request property. If a property with the key already
 * exists, overwrite its value with the new value.
 * ...
 */
public void setRequestProperty(String key, String value) {
    if (connected)
        throw new IllegalStateException("Already connected");
    if (key == null)
        throw new NullPointerException ("key is null");

    if (requests == null)
        requests = new MessageHeader();

    requests.set(key, value);
}

Where requests.set(key, value) do what you're asking for :)!

回答2:

this is back source code of setRequestProperty()

Sets the general request property. If a property with the key already exists, overwrite its value with the new value.

NOTE: HTTP requires all request properties which can legally have multiple instances with the same key to use a comma-seperated list syntax which enables multiple properties to be appended into a single property.

Parameters:

key the keyword by which the request is known (e.g., "accept"). value the value associated with it.

Throws: java.lang.IllegalStateException

if already connected java.lang.NullPointerException

if key is null See also: getRequestProperty(java.lang.String)

 public void setRequestProperty(String key, String value) {
    if (connected)
       throw new IllegalStateException("Already connected");
   if (key == null)
        throw new NullPointerException ("key is null");

    if (requests == null)
        requests = new MessageHeader();

   requests.set(key, value);
   }

Source Link

回答3:

I have found the way to view its implementation. Since it's abstract, must use Ctrl-Alt-B instead of Ctrl-B to view.

And the back source code of setRequestProperty as the following (inside jre\lib\rt.jar):

public void setRequestProperty(String var1, String var2) {
        if(this.connected) {
            throw new IllegalStateException("Already connected");
        } else if(var1 == null) {
            throw new NullPointerException("key is null");
        } else {
            if(this.isExternalMessageHeaderAllowed(var1, var2)) {
                this.requests.set(var1, var2);
            } 
        }
    }

来源：https://stackoverflow.com/questions/31872868/android-setrequestproperty-function-of-urlconnection-what-does-this-method-do

标签

java

android

httpurlconnection