基于oval注解支持JavaScript表达式约束条件

最新推荐文章于 2021-06-02 17:48:50 发布

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#oval #注解约束 #JavaScript表达式约束

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通常我们经常需要在接口中对DTO进行相关字段校验，我们可以采用传统的大量判断校验。目前我们采用使用基于oval（版本：1.90）注解约束，通过SpringAOP切面使用注解约束拦截。但是对于相关字段校验，如果字段跟其他字段有相关业务逻辑关系，，我们可以采用基于Oval javascript表达式约束，如果不依赖Mozilla Rhino，oval内部表达式引擎将会采用JSR223支持。

文章目录

1、oval简介

oval是一个开源验证框架，基于注解约束，功能强大，使用简单。
具体使用API文档可以查看：http://oval.sourceforge.net/userguide.html

我们查看API文档可看到如下说明：

OVal requires Java 5 or later - mainly for annotation support but other new language features (generics, for each loop, etc.) are used across the OVal source code too. Java 5 is actually the only hard requirement, depending on the features you want to use additional libraries are required:

AspectJ is required if you want to use the above mentioned programming by contract features.
Apache Commons JEXL is required if you want to define constraints via JEXL expressions.
BeanShell is required if you want to define constraints via BeanShell expressions.
Groovy is required if you want to define constraints via Groovy expressions.
JRuby is required if you want to define constraints via Ruby expressions.
Mozilla Rhino is required if you want to define constraints via JavaScript expressions.
MVEL is required if you want to define constraints via MVEL expressions.
OGNL is required if you want to define constraints via OGNL expressions.
XStream is required if you want to configure OVal via XML configuration files.
GNU Trove is required if you want to have OVal to internally use the GNU Trove high performance collections.
Javolution is required if you want to have OVal to internally use Javolution’s high performance collections.
JXPath is required if you want to use JXPath expressions for the constraint target declarations.
JUnit and all other libraries are required if you want to run the test cases.

其中：Mozilla Rhino is required if you want to define constraints via JavaScript expressions.（翻译：如果你想要他通过JavaScript表达式定义约束，Mozilla Rhino是必须的）

2、场景再现

假设咱们满足这样一个业务需求，如果男性时(sex=1)，年龄必须非空且大于0，否则提示“性别男性时，[年龄]不能为空且大于0”。

根据如上业务需求，我们可以采用@Check注解，我们查看API可以看到如下信息
The expr parameter holds the script to be evaluated. If the script returns true the constraint is satisfied. OVal provides two special variables:

_value - contains the value to validate (field value or getter return value)
_this - is a reference to the validated object

The lang parameter specifies the scripting language you want to use. In case the required libraries are loaded, OVal is aware of these languages:

bsh or beanshell for BeanShell,
groovy for Groovy,
jexl for JEXL,
js or javascript for JavaScript (via Mozilla Rhino),
mvel for MVEL,
ognl for OGNL,
ruby or jruby for Ruby (via JRuby)

Additional scripting languages can be registered via Validator.addExpressionLanguage(String, ExpressionLanguage).

这意味着我们可以采用javascript。

2.1、不引入Mozilla Rhino依赖

假设应用不引入Mozilla Rhino，代码示例如下：

import lombok.Data;
import net.sf.oval.Validator;
import net.sf.oval.constraint.Assert;

import java.util.Date;

/**
 * @description: 基于 oval 验证
 * @Date : 2018/10/8 下午6:07
 * @Author : 石冬冬-Seig Heil(dongdong.shi@mljr.com)
 */
@Data
public class Student {
    @Assert(expr="_value != null && _value > 0" ,lang="javascript",message="性别男性时，[年龄]不能为空且大于0"  ,when="javascript:_this.sex == 1")
    /**
     * 年龄
     */
    private Integer age;
    @Assert(expr="_value != null" ,lang="javascript",message="性别男性时，[入学日期]不能为空"  ,when="javascript:_this.sex == 1")
    /**
     * 入学日期
     */
    private Date enterDate;
    /**
     * 性别
     */
    private Integer sex;


    public static void main(String[] args) {
        Student student = new Student();
        student.setSex(1);
        student.setAge(0);
        //student.setEnterDate(new Date());
        Validator validator = new Validator();
        System.out.println(validator.validate(student).toString());
    }
}

然后运行结果

[net.sf.oval.ConstraintViolation: 性别男性时，[年龄]不能为空且大于0, net.sf.oval.ConstraintViolation: 性别男性时，[入学日期]不能为空]

这么来说，不引入Mozilla Rhino 依然是可以解析的，我们通过排查oval源码，查看@Assert注解的实现类，AssertCheck可以看到如下源码

 public boolean isSatisfied(final Object validatedObject, final Object valueToValidate, final OValContext context, final Validator validator)
            throws ExpressionEvaluationException, ExpressionLanguageNotAvailableException {
        final Map<String, Object> values = getCollectionFactory().createMap();
        values.put("_value", valueToValidate);
        values.put("_this", validatedObject);

        final ExpressionLanguage el = validator.getExpressionLanguageRegistry().getExpressionLanguage(lang);
        return el.evaluateAsBoolean(expr, values);
    }

这里有一个ExpressionLanguage，我们进而进入方法getExpressionLanguage
看到如下源码：

    /**
     *
     * @param languageId the id of the language, cannot be null
     *
     * @throws IllegalArgumentException if <code>languageName == null</code>
     * @throws ExpressionLanguageNotAvailableException
     */
    public ExpressionLanguage getExpressionLanguage(final String languageId) throws IllegalArgumentException, ExpressionLanguageNotAvailableException {
        Assert.argumentNotNull("languageId", languageId);

        ExpressionLanguage el = elcache.get(languageId);

        if (el == null)
            el = _initializeDefaultEL(languageId);

        if (el == null)
            throw new ExpressionLanguageNotAvailableException(languageId);

        return el;
    }

根据调试，进入_initializeDefaultEL方法，查看源码

private ExpressionLanguage _initializeDefaultEL(final String languageId) {
        // JavaScript support
        if (("javascript".equals(languageId) || "js".equals(languageId)) && ReflectionUtils.isClassPresent("org.mozilla.javascript.Context"))
            return registerExpressionLanguage("js", registerExpressionLanguage("javascript", new ExpressionLanguageJavaScriptImpl()));

        // Groovy support
        if ("groovy".equals(languageId) && ReflectionUtils.isClassPresent("groovy.lang.Binding"))
            return registerExpressionLanguage("groovy", new ExpressionLanguageGroovyImpl());

        // BeanShell support
        if (("beanshell".equals(languageId) || "bsh".equals(languageId)) && ReflectionUtils.isClassPresent("bsh.Interpreter"))
            return registerExpressionLanguage("beanshell", registerExpressionLanguage("bsh", new ExpressionLanguageBeanShellImpl()));

        // OGNL support
        if ("ognl".equals(languageId) && ReflectionUtils.isClassPresent("ognl.Ognl"))
            return registerExpressionLanguage("ognl", new ExpressionLanguageOGNLImpl());

        // MVEL2 support
        if ("mvel".equals(languageId) && ReflectionUtils.isClassPresent("org.mvel2.MVEL"))
            return registerExpressionLanguage("mvel", new ExpressionLanguageMVELImpl());

        // JRuby support
        else if (("jruby".equals(languageId) || "ruby".equals(languageId)) && ReflectionUtils.isClassPresent("org.jruby.Ruby"))
            return registerExpressionLanguage("jruby", registerExpressionLanguage("ruby", new ExpressionLanguageJRubyImpl()));

        // JEXL2 support
        if ("jexl".equals(languageId) && ReflectionUtils.isClassPresent("org.apache.commons.jexl2.JexlEngine"))
            return registerExpressionLanguage("jexl", new ExpressionLanguageJEXLImpl());

        // scripting support via JSR223
        if (ReflectionUtils.isClassPresent("javax.script.ScriptEngineManager")) {
            final ExpressionLanguage el = ExpressionLanguageScriptEngineImpl.get(languageId);
            if (el != null)
                return registerExpressionLanguage(languageId, el);
        }

        return null;
    }

这时，我们的languageId是javascript，我们可以看到第一个if条件判断，不成立，为啥呢，进一步看到一句

ReflectionUtils.isClassPresent("org.mozilla.javascript.Context")

内部源码：

 public static boolean isClassPresent(final String className) {
        try {
            Class.forName(className);
            return true;
        } catch (final ClassNotFoundException ex) {
            return false;
        }
    }

这意味着，通过反射查找相关表达式引擎类，如果没有引入Mozilla Rhino，则会走如下逻辑

// scripting support via JSR223
        if (ReflectionUtils.isClassPresent("javax.script.ScriptEngineManager")) {
            final ExpressionLanguage el = ExpressionLanguageScriptEngineImpl.get(languageId);
            if (el != null)
                return registerExpressionLanguage(languageId, el);
        }

2.2、JSR233

JSR233是什么呢？

JDK1.6开始，Java引入了JSR223 ，就是可以用一致的形式在JVM上执行一些脚本语言，如js脚本。
那么jsr223究竟是个什么东西？说通俗了，就是为各脚本引擎提供了统一的接口、统一的访问模式。在jsr223出现以前，如jdk1.4中，就已经可以直接调用js引擎（可从http://www.mozilla.org/rhino/下载）来运行js脚本了，只不过调用的时候是与js引擎的实现息息相关的，jsr223的引入，调用者与具体脚本引擎解耦了，调用类里，不再需要引入具体引擎相关的类。如果有两个脚本引擎所支持的语言语法相似，还可以直接更换scriptEngineManager.getEngineByName(“javascript”)中的引擎名称，以方便的切换引擎。

来个JSR代码示例

/**
 * @description: Script测试
 * @Date : 2018/10/9 下午2:21
 * @Author : 石冬冬-Seig Heil(dongdong.shi@mljr.com)
 */
public class ScriptTest {
    @Test
    public void script(){
        try {
            ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
            ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("javascript");
            System.out.println("2*6-(6+5) 结果："+scriptEngine.eval("2*6-(6+5)"));
            System.out.println("1>2?true:false 结果："+scriptEngine.eval("1>2?true:false"));
            scriptEngine.put("a","1");
            scriptEngine.put("b","5");
            scriptEngine.put("c","2");
            System.out.println("(a >b || c < b) ?  (a + b) : (a - b) 结果："+scriptEngine.eval("(a >b || c < b) ?  (a + b) : (a - b)"));
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

运行结果

2*6-(6+5) 结果：1
1>2?true:false 结果：false
(a >b || c < b) ? (a + b) : (a - b) 结果：15

2.3、引入Mozilla Rhino

Rhino 是一个纯 Java 的开源的 JavaScript 实现，rhino是使用java代码实现的javascript解释器，它实现了javascript的核心，符合Ecma-262标准，支持javascript标准的所有特性。

Rhino 提供了如下功能

对 JavaScript 1.5 的完全支持
直接在 Java 中使用 JavaScript 的功能
一个 JavaScript shell 用于运行 JavaScript 脚本
一个 JavaScript 的编译器，用于将 JavaScript 编译成 Java 二进制文件

官网：
http://www.mozilla.org/rhino/
http://www.mozilla.org/rhino/ScriptingJava.html

maven添加如下依赖

        <dependency>
            <groupId>org.mozilla</groupId>
            <artifactId>rhino</artifactId>
            <version>1.7R4</version>
        </dependency>

引入后，则会走如下逻辑

// JavaScript support
        if (("javascript".equals(languageId) || "js".equals(languageId)) && ReflectionUtils.isClassPresent("org.mozilla.javascript.Context"))
            return registerExpressionLanguage("js", registerExpressionLanguage("javascript", new ExpressionLanguageJavaScriptImpl()));

ExpressionLanguageJavaScriptImpl源码如下

/**
 * @author Sebastian Thomschke
 */
public class ExpressionLanguageJavaScriptImpl extends AbstractExpressionLanguage {
    private static final Log LOG = Log.getLog(ExpressionLanguageJavaScriptImpl.class);

    private final Scriptable parentScope;

    private final ObjectCache<String, Script> scriptCache = new ObjectCache<String, Script>();

    public ExpressionLanguageJavaScriptImpl() {
        final Context ctx = ContextFactory.getGlobal().enterContext();
        try {
            parentScope = ctx.initStandardObjects();
        } finally {
            Context.exit();
        }
    }

    public Object evaluate(final String expression, final Map<String, ?> values) throws ExpressionEvaluationException {
        LOG.debug("Evaluating JavaScript expression: {1}", expression);
        try {
            final Context ctx = ContextFactory.getGlobal().enterContext();
            Script script = scriptCache.get(expression);
            if (script == null) {
                ctx.setOptimizationLevel(9);
                script = ctx.compileString(expression, "<cmd>", 1, null);
                scriptCache.put(expression, script);
            }
            final Scriptable scope = ctx.newObject(parentScope);
            scope.setPrototype(parentScope);
            scope.setParentScope(null);
            for (final Entry<String, ?> entry : values.entrySet()) {
                scope.put(entry.getKey(), scope, Context.javaToJS(entry.getValue(), scope));
            }
            return script.exec(ctx, scope);
        } catch (final EvaluatorException ex) {
            throw new ExpressionEvaluationException("Evaluating JavaScript expression failed: " + expression, ex);
        } finally {
            Context.exit();
        }
    }
}

3、最佳实践

目前我们采用SpringAOP切面，拦截相关方法，获取DTO注解解析约束规则，并返回校验信息源码如下：

/**
 * @description: 基于oval的注解的DTO约束校验
 * <pre>
 *     如果基于oval，需要支持javascript表达式，需要引入
 *     <!-- https://mvnrepository.com/artifact/org.mozilla/rhino -->
 *     <dependency>
 *         <groupId>org.mozilla</groupId>
 *         <artifactId>rhino</artifactId>
 *         <version>1.7R4</version>
 *     </dependency>
 * </pre>
 * @Date : 2018/6/2 下午2:32
 * @Author : 石冬冬-Seig Heil(dongdong.shi@mljr.com)
 */
@Aspect
@Component
public class OvalValidatorAdvice {

    private Logger log = LoggerFactory.getLogger(this.getClass());
    @Autowired
    private Validator validator;

    @Pointcut("@annotation(com.mljr.annotation.OvalValidator)")
    public void validator() {
    }

    @Around("validator()")
    public Object intercept(ProceedingJoinPoint joinPoint) throws Throwable {
        Method method = ((MethodSignature) joinPoint.getSignature()).getMethod();
        OvalValidator annotation = method.getAnnotation(OvalValidator.class);
        if (annotation == null) {
            return joinPoint.proceed();
        }
        String module = annotation.value();
        String action = "";
        action = annotation.action().value();
        if(StringTools.isNotEmpty(action)){
            action = MessageFormat.format(",action={0}",action);
        }
        Class<?> targetClass = joinPoint.getTarget().getClass();
        String className = targetClass.getName();
        String target = className + "." + method.getName();
        Object args[] = joinPoint.getArgs();
        log.info("[OvalValidator Request]{}{},target={},dto={}",module,action,target,JSON.toJSON(args));
        if (args == null || args.length == 0) {
            log.warn("该方法缺少校验参数 ");
            return joinPoint.proceed();
        }
        List<ConstraintViolation> violations = validator.validate(args[0]);
        if (CollectionsTools.isNotEmpty(violations)) {
            return Result.fail(RemoteEnum.ERROR_WITH_EMPTY_PARAM.getIndex(), violations.get(0).getMessage());
        }
        return joinPoint.proceed();
    }
}

其中，@OvalValidator是个自定义注解

/**
 * @Description 基于oval的注解的DTO约束校验注解
 * @Date : 2018/6/2 下午2:32
 * @Author : 石冬冬-Seig Heil(dongdong.shi@mljr.com)
 */
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface OvalValidator {
    /**
     * 模块名称
     * 请注意，如果不定义请使用module值
     * @return
     */
    String value() default "未知模块";
    /**
     * 动作
     * @return
     */
    Action action() default @Action();
}

oval的Validator 该对象纳入Spring Bean容器管理

/**
 * @description: 基于Oval注解约束配置
 * @Date : 2018/10/8 下午7:30
 * @Author : 石冬冬-Seig Heil(dongdong.shi@mljr.com)
 */
@Configuration
@Slf4j
public class OvalValidatorConfig {

    @Bean
    public Validator ovalValidatorInit(){
        Validator validator = new Validator();
        try {
            validator.getExpressionLanguageRegistry().registerExpressionLanguage("javascript",new ExpressionLanguageJavaScriptImpl());
        } catch (Exception e) {
            log.warn("OvalValidatorConfig focus an warning={}",e.getMessage());
        }finally {
            log.info("OvalValidatorConfig initializing done.");
        }
        return validator;
    }
}

归纳：如果Validator注册ExpressionLanguageJavaScriptImpl该表达式实现类，意味着需要引入Mozilla Rhino。不引入该依赖时，采用JSR223内置解析表达式。对于大量DTO业务校验，我们采用validator纳入SpringBean容器管理初始化，无需每次实例创建，引擎表达式注册。

参考文章：
http://oval.sourceforge.net/userguide.html

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