A Nicholas Sparks movie crossed with a Blue Buffalo dog food commercial, “A Dog’s Purpose” was perhaps best described by Griffin McElroy on the “My Brother, My Brother and Me” podcast, based solely on the trailer: “What’s everybody’s favorite part of ‘Marley and Me’? The end of it. So what if we just made a movie that was the end of ‘Marley and Me,’ over and over, forever?”

Did I shed some tears over the doggy demises in this movie? Admittedly, yes. Does that reaction make the movie any less shameless for relying upon death to create poignancy? It does not.

It’s not a spoiler to reveal that the titular purpose is revealed to be the love of human beings, and our four-legged hero (voiced by Josh Gad in wall-to-wall narration) keeps coming back to life as different breeds, mainly but not entirely to take care of Ethan. In the 1960s Ethan (Bryce Gheisar) and his mom (Juliet Rylance, “The Knick”) rescue a retriever from the hot cab of a pickup truck, take him home, and dub him Bailey. (Because of the affectionate way the boy addresses him, the dog thinks his name is “Bailey-Bailey-Bailey-Bailey.”

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Ethan could use a friend — his dad (Luke Kirby, “Rectify”) is obsessed with work disappointments and starts drinking more and more heavily. By the time Ethan is a high-school football star (now played by K.J. Apa, the Archie Andrews of the new “Riverdale”), dad’s a full-blown alcoholic, but Ethan and Bailey remain close, even as Ethan falls for Hannah (Britt Robertson). They’ve got big plans to go off to college together, but tragedy and self pity tear them apart, and Bailey is left to grow old and alone on the family farm. And then he dies.

He comes back as a female German Shepherd police dog in 1970s Chicago, providing loyal service to officer Carlos (John Ortiz, “Silver Linings Playbook”). And then she dies. Then he’s a Corgi who helps his lonely lady Maya (Kirby Howell-Baptiste) find love with her college classmate Al (the appropriately-named Pooch Hall). Maya and Al get married and have a family. Then the dog dies.

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An older Ethan (Dennis Quaid) and Hannah (Peggy Lipton), photogenic as ever, come back into the picture in the last dog-life that we see, in which our hero’s soul returns as a hound that’s ignored and abandoned by its down-and-out owners. (The movie has a classist streak a mile wide: people with nice houses and apartments are good to their dogs, while poor people — who apparently get all the bad weather — leave their pets chained in the yard.)

Adapting the book by W. Bruce Cameron, screenwriter Cathryn Michon makes the onscreen spoken dialogue far less prominent than the talking, talking, talking that Gad does on the soundtrack. And while Josh Gad can be charming and funny as part of an ensemble, a little of his winsome, I’m-a-cute-widdle-doggie narration here goes a very long way.

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The human actors who appear on camera know they’re playing second fiddle to a bevy of engaging animals, and they do their best to make an impression with what they’ve got. The Robertson-Apa and Lipton-Quaid pairings offer maximum adorability as performed (and minimal depth as written), and Ortiz packs a lot of sad subtext into just a few scenes. (Logan Miller, so memorable in “Take Me to the River” and “Stanford Prison Experiment,” gives off a vibe of creepiness that seems better suited to a darker movie, but that’s more on director Lasse Hallstrom for not guiding the actor into this film’s Hallmark-y mode.)

“A Dog’s Purpose” offers many of the highlights of human-canine relations at their warmest and most affectionate, but the film chooses to skim on sun-dappled surfaces (Terry Stacey of “Elvis and Nixon” was the cinematographer) and sentimentality (Rachel Portman’s score bombards the heartstrings) when it might have gone deeper. Not that every animal movie has to go as dark as “Wiener-Dog” or as existential as “Au Hasard Balthazar,” but this much saccharine isn’t healthy for animals or humans.