Sen. John Glenn (D-Ohio) won New Jersey's non-binding Democratic straw poll here today, defeating former vice president Walter F. Mondale and the rest of the Democratic field in a contest largely ignored by the candidates.

Glenn, benefiting from a personal appearance at the convention this morning, gave his presidential campaign a boost by winning 432, or 38 percent, of the 1,125 votes cast. Mondale, who chose not to contest the straw vote, received 317, or 28 percent.

The "uncommitted" line on the ballot drew 294 votes, or 26 percent, after some delegates mounted a campaign to send a message that they were not impressed with any of the announced candidates. Of those, 187 said they had no preference, while the rest cast their votes for various non-candidates.

Among other announced candidates, Sen. Gary Hart (D-Colo.) received 41, or 4 percent; Sen. Ernest F. Hollings (D-S.C.), who made a last-minute appearance here this morning, 26, or 2 percent; Sen. Alan Cranston (D-Calif), 12 or 1 percent; while former Florida governor Reubin Askew and former South Dakota senator George McGovern received 3 and 2 votes, respectively. Another potential candidate, the Rev. Jesse L. Jackson polled 67 votes, or 6 percent.

All candidates officially said they were bypassing the straw poll, but Glenn's staff appeared to make a greater effort to contact the delegates.

Mondale officials dismissed the outcome. "It comes as no surprise to us," Robert Beckel, Mondale's campaign manager, said in a telephone interview. "I don't think it's difficult to win a contest with no opposition. We chose not to compete and we didn't."

But the outcome here today probably will put added pressure on Mondale to do well in the Maine straw poll. Mondale's decision not even to address the convention appeared to have hurt him, as delegates grumbled that the candidates were taking them for granted.

Sen. Frank Lautenberg (D-N.J.) echoed those feelings this morning, shortly before Glenn spoke to the delegates, when he told the audience, "I know we'd like to see more presidential candidates present. Every campaign makes a few mistakes. We'll allow the candidates one mistake in judgment."

Mondale's campaign decided earlier this year not to mount a serious effort here, deciding instead to concentrate on the Oct. 1 Maine straw poll. Glenn, while announcing that he would make no special effort to win straw polls, campaigned four times here in the past three months in addition to the contacts made by his staff here. The movement to put the delegates on record in opposition to all the candidates by voting "uncommitted" was in part an effort to lure other candidates, particularly Sen. Edward M. Kennedy (D-Mass.), into the race.

Glenn got a warm reception here and tried to capitalize on the absence of his chief Democratic rival. Noting that fortunes are won or lost in hours in Atlantic City, the relaxed Glenn said, "I'm not going to place any bets on the outcome of the straw poll , but four more years of the Reagan administration is a gamble we can't afford to take."

In his remarks, Hollings took dead aim at Glenn for supporting President Reagan's tax cut bill in 1981 and added that Glenn's standing as an ex-astronaut was no match for Reagan's standing as an ex-movie star.