The Astros sent Minor League infielder Cody Bohanek along with Davis. To Houston, the Mets sent outfielder Ross Adolph, infielder Luis Santana and catcher Scott Manea.
From Cleveland, the club acquired right-hander Walker Lockett and infielder Sam Haggerty.
Plawecki's fit in New York came into question after the club signed All-Star catcher Wilson Ramos to a two-year, $19 million deal last month, which created a logjam behind the plate with Travis d'Arnaud, to whom the club tendered a contract earlier this offseason. d'Arnaud is expected to return from Tommy John surgery early next season. And even after Sunday's trades, the club also has catcher Tomas Nido on its 40-man roster.
Plawecki, a career .218/.308./.330 hitter over parts of four seasons, should essentially slot in for Yan Gomes, who was traded from the Indians to the Nationals on Nov. 30.
Davis, a third-round Draft pick by Houston in 2014, is coming off a season in which he won the Pacific Coast League batting title, hitting .342 with Triple-A Fresno. He broke into the Majors in 2017, and he's played in 66 big league games over the last two seasons, slashing .194/.260/.321 with five homers.
"J.D. is a versatile offensive talent," Mets general manager Brodie Van Wagenen said in a statement. "He's young, had success vs. lefties and he'll provide depth at the corner positions."
Bohanek has 17 doubles, nine homers, 18 stolen bases and 55 RBIs in 177 career Minor League games.
Adolph was the Mets' 12th-round pick in 2018 and batted .276 with nine doubles, 12 triples, seven homers and 35 RBIs in 61 games for Class A Short Season Brooklyn last season. Santana hit .348/.446/.471 with four homers and 35 RBIs in 53 games with Rookie-level Kingsport in 2018. Last season, Manea batted .261 with 23 doubles, 12 homers and 53 RBIs in 100 games for Class A Columbia.
Lockett made his big league debut last year, making four appearances, including three starts, with the Padres. He was a fourth-round Draft pick by San Diego in 2012, and he led the PCL last season in starts (23), innings (133 1/3) and strikeouts (118), going 5-9 with a 4.73 ERA. The Padres traded Lockett to Cleveland on Nov. 20.
"We continue to focus on acquiring young, Major League-ready talent for 2019 and beyond," Van Wagenen said. "Still only 24 years old, Walker provides us valuable depth to our starting rotation."
Haggerty hit .243/.373/.396 with 21 doubles, four homers and 24 stolen bases in 87 games for Double-A Akron in 2018. He was a mid-season and postseason Carolina League All-Star in 2017 after batting .253 with 27 doubles, 13 triples, three homers and 49 stolen bases in 112 games with Class A Advanced Lynchburg.
"Sam is athletic with good speed and a strong arm," Van Wagenen said.