Lambda2sql (lambda) -> "sql"

Please note: This is a Java 10 library so make sure you have at least Java 10 installed when using it.

Convert Java 8 lambdas to SQL statements.

For example, the following SqlPredicate<Person>:

 person -> person.getAge() < 100 && person.getHeight() > 200

is converted to a string:

  person.age < 100 AND person.height > 200

allowing you to write readable queries in a type safe way.

Usage

int age = 100;
int height = 200;
SqlPredicate<Person> predicate = person -> person.getAge() < age && person.getHeight() > height;

String sql = Lambda2Sql.toSql(predicate); // person.age < 100 AND person.height > 200

How it works

It uses JaQue to build an expression tree for a lambda. The expression tree is then traversed and converted to a SQL statement.

Under the hood, JaQue depends on the system property jdk.internal.lambda.dumpProxyClasses, if the lambda expression is not serialized: See https://bugs.openjdk.java.net/browse/JDK-8023524.

When the property is enabled, JVM generated classes for lambdas are saved to disk. JaQue then uses ASM to read the .class files and creates expression trees.

Since the functional interfaces included in this project are automatically serialized, there is no need to set this property. The interfaces SqlPredicate<T> and SqlFunction<T> can be used exactly like the original functional interfaces.

Features

Current version works with predicates, functions and supports the following operators: >, >=, <, <=, =, !=, &&, ||, !

It is also possible to achieve LIKE operations using the String startsWith, endsWith and contains methods. For example, the lambda expression
person -> person.getAge() > 18 && person.getName().startsWith("Steve")
would translate to:
person.age > 18 AND person.name LIKE 'Steve%'

Feel free to open an issue with any requests you might have.

Install

You can include the Maven dependency:

<dependency>
    <groupId>com.github.collinalpert</groupId>
    <artifactId>lambda2sql</artifactId>
    <version>2.0</version>
</dependency>

Or add the JAR to your project.