Yes please water bath and add lemon juice or citric acid. If the tomatoes are on the lower end of acidity, they might not be acid enough for safety. The method used above can result in a sealed jar. But you are sealing in anything that went into the jar, like spores. You will also have some air left in that will hasten spoilage or oxidation changes. Here is a link for current recommendations for tomato juice canning;
http://nchfp.uga.edu/how/can_03/tomato_juice.html