Hint

This article is generated by AI translation.

Custom Rules

When dbVisitor built-in rules cannot meet your needs, you can extend with custom rules by implementing the SqlRule interface.

Implementation Steps

1. Implement the SqlRule interface

import net.hasor.dbvisitor.dynamic.QueryContext;
import net.hasor.dbvisitor.dynamic.SqlArgSource;
import net.hasor.dbvisitor.dynamic.SqlBuilder;
import net.hasor.dbvisitor.dynamic.rule.SqlRule;
import net.hasor.dbvisitor.internal.OgnlUtils;
import net.hasor.cobble.StringUtils;

public class MyRule implements SqlRule {
    @Override
    public boolean test(SqlArgSource data, QueryContext context, String activeExpr) {
        // activeExpr is the "activation condition" in @{ruleName, activation condition, rule content}
        // Return true to indicate the rule should execute
        return StringUtils.isBlank(activeExpr) || Boolean.TRUE.equals(OgnlUtils.evalOgnl(activeExpr, data));
    }

    @Override
    public void executeRule(SqlArgSource data, QueryContext context,
                            SqlBuilder sqlBuilder, String activeExpr, String ruleValue) {
        // ruleValue is the "rule content" in @{ruleName, activation condition, rule content}
        // Use sqlBuilder to assemble the generated SQL fragment
        sqlBuilder.appendSql("my_custom_value");
    }
}

2. Register the rule (choose one)

// Method 1: Register via Configuration (recommended)
Configuration config = new Configuration();
config.addSqlRule("myrule", new MyRule());

// Method 2: Register to the global default registry
RuleRegistry.DEFAULT.register("myrule", new MyRule());

3. Use the rule

select * from users where id = @{myrule, true, xxxx}

Interface Description

The SqlRule interface defines two methods:

Method	Description
test(data, context, activeExpr)	Determines whether the rule should execute. If false, the entire @{...} is skipped.
executeRule(data, context, sqlBuilder, activeExpr, ruleValue)	Executes the rule logic, assembling SQL fragments and arguments via sqlBuilder.

Argument parsing rule: In @{ruleName, activeExpr, ruleValue}, content before the first comma is the rule name, content before the second comma is activeExpr, and everything after is ruleValue.

Hint

Rule names are case-insensitive. A rule registered as "myrule" can be invoked via @{MyRule}, @{MYRULE}, etc.