1.1.3. 訊息頭

HTTP訊息可以包含多個描述該訊息屬性的頭部諸如內容長度，內容型別等，HttpClient的提供方法來檢索，新增，刪除和列舉這些頭部。

HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, 
    HttpStatus.SC_OK, "OK");
response.addHeader("Set-Cookie", 
    "c1=a; path=/; domain=localhost");
response.addHeader("Set-Cookie", 
    "c2=b; path=\"/\", c3=c; domain=\"localhost\"");
Header h1 = response.getFirstHeader("Set-Cookie");
System.out.println(h1);
Header h2 = response.getLastHeader("Set-Cookie");
System.out.println(h2);
Header[] hs = response.getHeaders("Set-Cookie");
System.out.println(hs.length);

輸出內容為 >

Set-Cookie: c1=a; path=/; domain=localhost
Set-Cookie: c2=b; path="/", c3=c; domain="localhost"
2

獲得所有頭部給定型別的最有效的方法是使用
HeaderIterator 介面.

HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, 
    HttpStatus.SC_OK, "OK");
response.addHeader("Set-Cookie", 
    "c1=a; path=/; domain=localhost");
response.addHeader("Set-Cookie", 
    "c2=b; path=\"/\", c3=c; domain=\"localhost\"");

HeaderIterator it = response.headerIterator("Set-Cookie");

while (it.hasNext()) {
    System.out.println(it.next());
}

輸出內容為 >

Set-Cookie: c1=a; path=/; domain=localhost
Set-Cookie: c2=b; path="/", c3=c; domain="localhost"

它還提供了方便的方法來解析HTTP訊息成為獨立頭部元素。

HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, 
    HttpStatus.SC_OK, "OK");
response.addHeader("Set-Cookie", 
    "c1=a; path=/; domain=localhost");
response.addHeader("Set-Cookie", 
    "c2=b; path=\"/\", c3=c; domain=\"localhost\"");

HeaderElementIterator it = new BasicHeaderElementIterator(
    response.headerIterator("Set-Cookie"));

while (it.hasNext()) {
    HeaderElement elem = it.nextElement(); 
    System.out.println(elem.getName() + " = " + elem.getValue());
    NameValuePair[] params = elem.getParameters();
    for (int i = 0; i < params.length; i++) {
        System.out.println(" " + params[i]);
    }
}

輸出內容為 >

c1 = a
path=/
domain=localhost
c2 = b
path=/
c3 = c
domain=localhost