The nine-dash line claims were invalidated on the grounds that controlling small islands without permanent settlement doesn't extend the EEZ, so the EEZ is limited to 200 nautical miles from the coastline. But there's a lot within 200 nmi from the Chinese coast, including the Paracels, where those Vietnamese fishermen in the article were attacked by the Chinese coast guard. Simply defending their EEZ, as they have every right to do. Except the Paracels are also within 200 nmi of the Vietnamese coast, so the maritime boundary is up for negotiation. Vietnam and China have a treaty delineating the boundary in the Gulf of Tonkin, but otherwise it's still unspecified.
As for Japan, they're on the other side of Taiwan, so their EEZ doesn't extend nearly far enough to make any claims in the South China Sea.
https://en.wikipedia.org/wiki/Maritime_Delimitation_in_the_B...
Vietnam should bring the case to court and employ some good negotiators. It's the only potentially constructive strategy for them, as outmuscling China is out of the question. If China won't respect the court's decision, the international community can then condemn them, issue tariffs and sanctions and Vietnam could legally fire warning shots and sink their coast guard vessles entering its EEZ.
I wish Japan would extend its navy and actively deter China. Too bad Mr. Abe had to resign his post serving as PM, he wanted to revisit article 9 of Japan's constitution. An reiterpretation was made allowing Japan to exercise collective self defense.