Sun Microsystems Inc. said Tuesday that it will purchase SeeBeyond Technology Corp. for $387 million in cash, sending shares of the Monrovia-based provider of business-integration software surging as much as 31 percent.

Under the agreement, Santa Clara-based Sun said it will pay $4.25 a share, a 30 percent premium to SeeBeyond’s Monday closing price of $3.28. The deal includes the assumption of employee stock options.

The acquisition of SeeBeyond is seen as a way to build on Sun’s Java platform operations. SeeBeyond uses Java-based technology in software that helps businesses tie together multiple applications and systems that have been individually developed.

“This transaction will combine the leader in Java and Web services with a leader in integration, bringing to market what we believe to be the most comprehensive and productive application development platform suite available today,” said Jim Demetriades, founder and chief executive officer at SeeBeyond.

The purchase is expected to be completed in early fall, subject to regulatory approval and approval by SeeBeyond shareholders. When the transaction closes, SeeBeyond will be integrated with Sun, the companies said.

The two companies had previously established a partnership in October 2004 to integrate their product lines to deliver a more complete package for their customers, Sun and SeeBeyond said in a joint statement.

The deal follows Sun’s recent plans to acquire storage equipment maker Storage Technology Corp. for $4.1 billion to boost Sun’s presence in the market for data storage.

Shares of SeeBeyond, which had revenue of $167 million in the past 12 months, jumped 30.8 percent to settle at $4.29 on Tuesday.