remove redundant null check in ResponseHeader.lastModified

added a JUnit testcase for ResponseHeader dates (using age()),
adjusted age() to pass all tests

source/net/yacy/cora/protocol/ResponseHeader.java

@@ -32,10 +32,11 @@ public class ResponseHeader extends HeaderFramework {
 
     private static final long serialVersionUID = 0L;
 
+    // cached values for quicker repeated access
     private Date date_cache_Date = null;
     private Date date_cache_Expires = null;
     private Date date_cache_LastModified = null;
-    
+
     public ResponseHeader(final int statusCode) {
         super();
         this.put(HeaderFramework.STATUS_CODE, Integer.toString(statusCode));
@@ -67,7 +68,11 @@ public class ResponseHeader extends HeaderFramework {
             return 200;
         }
     }
-    
+
+    /**
+     * Get the http field Date or now (if header date missing)
+     * @return date message was created or now
+     */
     public Date date() {
         if (this.date_cache_Date != null) return this.date_cache_Date;
         final Date d = headerDate(HeaderFramework.DATE);
@@ -76,26 +81,36 @@ public class ResponseHeader extends HeaderFramework {
         return this.date_cache_Date;
     }
 
+    /**
+     * get http field Expires if available
+     * @return date or null
+     */
     public Date expires() {
         if (this.date_cache_Expires != null) return this.date_cache_Expires;
         this.date_cache_Expires = headerDate(HeaderFramework.EXPIRES);
         return this.date_cache_Expires;
     }
 
+    /**
+     * get http field Last-Modified or now (if header field is missing)
+     * @return valid date (always != null)
+     */
     public Date lastModified() {
         if (this.date_cache_LastModified != null) return this.date_cache_LastModified;
         Date d = headerDate(HeaderFramework.LAST_MODIFIED);
-        if (d == null) d = date();
         final Date now = new Date();
         this.date_cache_LastModified = (d == null) ? date() : d.after(now) ? now : d;
         return this.date_cache_LastModified;
     }
 
+    /**
+     * age in milliseconds (difference between now and last_modified)
+     * @return age in milliseconds
+     */
     public long age() {
         final Date lm = lastModified();
-        final Date sd = date();
+        final Date now = new Date();
-        if (lm == null) return Long.MAX_VALUE;
+        return now.getTime() - lm.getTime();
-        return ((sd == null) ? new Date() : sd).getTime() - lm.getTime();
     }
 
     public boolean gzip() {

test/net/yacy/cora/protocol/ResponseHeaderTest.java

@@ -0,0 +1,135 @@
+package net.yacy.cora.protocol;
+
+import java.util.Date;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class ResponseHeaderTest {
+
+    /**
+     * Test of age method, of class ResponseHeader.
+     * testing many combination of header.date and header.last_modified
+     * test goal: age is suppose to always >= 0
+     */
+    @Test
+    public void testAge() {
+        // because ResponseHeader caches date values internally on 1st access,
+        // we need to create a new instance for every testcase
+
+        ResponseHeader testhdr1 = new ResponseHeader(200);
+        ResponseHeader testhdr2 = new ResponseHeader(200);
+        ResponseHeader testhdr3 = new ResponseHeader(200);
+
+        // access-sequence 1 = age() without accessing any date before
+        // access-sequence 2 = access date() then age()
+        // access-sequence 3 = access lastModified() then age()
+
+        // test case with sorce: date=null lastmodified=null
+        long age1 = testhdr1.age();
+
+        testhdr2.date();
+        testhdr3.lastModified();
+
+        assertEquals("access-sequence 1 date=null lastmod=null AGE="+age1, 0, age1);
+
+        testhdr2.lastModified();
+
+        long age2 = testhdr2.age();
+        assertEquals("access-sequence 2 date=null lastmod=null AGE="+age2, 0, age2);
+
+        testhdr3.date();
+
+        long age3 = testhdr3.age();
+        assertEquals("access-sequence 3 date=null lastmod=null AGE="+age3, 0, age3);
+
+        Date past = new Date(System.currentTimeMillis() / 2);
+        Date future = new Date(System.currentTimeMillis() * 2);
+
+        Date[] testdate = new Date[3];
+        testdate[0] = past;
+        testdate[1] = new Date();
+        testdate[2] = future;
+        String[] testdatename = new String[] {"past","now","future"}; // date names just for output
+
+        for (int id = 0; id < testdate.length; id++) {
+
+            // test case with sorce: date=testdate(x) lastmodified=null
+            testhdr1 = new ResponseHeader(200);
+            testhdr1.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+            testhdr2 = new ResponseHeader(200);
+            testhdr2.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+            testhdr3 = new ResponseHeader(200);
+            testhdr3.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+
+            age1 = testhdr1.age();
+            testhdr2.date();
+            testhdr3.lastModified();
+
+            assertTrue("access-sequence 1."+id+" date=" + testdatename[id] + " lastmod=null AGE= " + age1, age1 >= 0);
+
+            age2 = testhdr2.age();
+            assertTrue("access-sequence 2."+id+" date=" + testdatename[id] + " lastmod=null AGE= " + age2, age2 >= 0);
+
+            age3 = testhdr3.age();
+            assertTrue("access-sequence 3."+id+" date=" + testdatename[id] + " lastmod=null AGE= " + age3, age3 >= 0);
+
+            // test case with sorce: date=null lastmodified=testdat(x)
+            testhdr1 = new ResponseHeader(200);
+            testhdr1.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[id]));
+            testhdr2 = new ResponseHeader(200);
+            testhdr2.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[id]));
+            testhdr3 = new ResponseHeader(200);
+            testhdr3.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[id]));
+
+            age1 = testhdr1.age();
+            testhdr2.date();
+            testhdr3.lastModified();
+
+            assertTrue("access-sequence 1."+id+" date=null lastmod=" + testdatename[id] + " AGE= " + age1, age1 >= 0);
+
+            age2 = testhdr2.age();
+            assertTrue("access-sequence 2."+id+" date=null lastmod=" + testdatename[id] + " AGE= " + age2, age2 >= 0);
+
+            age3 = testhdr3.age();
+            assertTrue("access-sequence 3."+id+" date=null lastmod=" + testdatename[id] + " AGE= " + age3, age3 >= 0);
+
+            for (int imd = 0; imd < testdate.length; imd++) {
+                // test case with sorce: date=testdate(x) lastmodified=testdate(y)
+                testhdr1 = new ResponseHeader(200);
+                testhdr1.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+                testhdr1.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[imd]));
+
+                testhdr2 = new ResponseHeader(200);
+                testhdr2.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+                testhdr2.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[imd]));
+
+                testhdr3 = new ResponseHeader(200);
+                testhdr3.put(HeaderFramework.DATE, HeaderFramework.formatRFC1123(testdate[id]));
+                testhdr3.put(HeaderFramework.LAST_MODIFIED, HeaderFramework.formatRFC1123(testdate[imd]));
+
+                age1 = testhdr1.age();
+
+                testhdr2.date();
+                testhdr3.lastModified();
+
+                assertTrue("case 1."+id+"."+imd+" date=" + testdatename[id] + " lastmod=" + testdatename[imd] + " AGE= " + age1, age1 >= 0);
+
+                // hint to mismatch of date
+                Date d1 = testhdr1.date();
+                Date m1 = testhdr1.lastModified();
+                if (d1.before(m1)) {
+                    System.err.println("this faulty combination with lastmod after date (date="+testdatename[id]+" lastmod="+testdatename[imd]+") is accepted without correction");
+                }
+
+                age2 = testhdr2.age();
+                assertTrue("case 2."+id+"."+imd+" date=" + testdatename[id] + " lastmod=" + testdatename[imd] + " AGE= " + age2, age2 >= 0);
+
+                age3 = testhdr3.age();
+                assertTrue("case 3."+id+"."+imd+" date=" + testdatename[id] + " lastmod=" + testdatename[imd] + " AGE= " + age3, age3 >= 0);
+            }
+
+        }
+
+    }
+
+}