MyBatis-Plus v3.4.0 新的分页插件 报 java.lang.IndexOutOfBoundsException 错误

版本 v3.4.0

使用分页方法，BaseMapper中的selectPage方法

重现步骤(如果有就写完整)

@SpringBootTest
class AdminApplicationTests {

    @Autowired
    private UserService userService;
    @Autowired
    private UserMapper userMapper;
    @Autowired
    private PasswordMatcher passwordMatcher;

    @Test
    void contextLoads() {
        Page<User> userPage = new Page<>(1, 20);
        Page<User> page = this.userMapper.selectPage(userPage, null);
        System.out.println(page);
    }
}
运行单测之后直接报错，报错信息看下面。我看了一下 PaginationInnerInterceptor的源码，发现有个地方写的有点迷，我是没看懂，请求解释：
```java
@Override
    public boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
        IPage<?> page = ParameterUtils.findPage(parameter).orElse(null);
        if (page == null || page.getSize() < 0 || !page.isSearchCount()) {
            return true;
        }

        BoundSql countSql;
        MappedStatement countMs = buildCountMappedStatement(ms, page.countId());
        if (countMs != null) {
            countSql = countMs.getBoundSql(parameter);
        } else {
            countMs = buildAutoCountMappedStatement(ms);
            String countSqlStr = autoCountSql(page.optimizeCountSql(), boundSql.getSql());
            PluginUtils.MPBoundSql mpBoundSql = PluginUtils.mpBoundSql(boundSql);
            countSql = new BoundSql(countMs.getConfiguration(), countSqlStr, mpBoundSql.parameterMappings(), parameter);
            PluginUtils.setAdditionalParameter(countSql, mpBoundSql.additionalParameters());
        }

        CacheKey cacheKey = executor.createCacheKey(countMs, parameter, rowBounds, countSql);
       // 注意：这一行是问题代码，返回的PageList对象（继承自ArrayList的一个final类），然后就直接get(0)了
        Object result = executor.query(countMs, parameter, rowBounds, resultHandler, cacheKey, countSql).get(0);
        page.setTotal(result == null ? 0L : Long.parseLong(result.toString()));
        return continuePage(page);
    }

而继续看PageList对象：

@Data
@AllArgsConstructor
@EqualsAndHashCode(callSuper = true)
public final class PageList<T> extends ArrayList<T> {

    /**
     * 记录数
     */
    private List<T> records;

    /**
     * 总数
     */
    private long total;

}

What？？就是这么简单，那么这个对象的get(0)能拿到什么？ 再看一下executor的query方法返回什么：

.... 省略若干行代码
result = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
                        List<E> records = (List<E>) result;
                        page.setRecords(records);
                        tcm.putObject(cache, key, records);
                        if (countCacheKey != null && !page.isHitCount()) {
                            tcm.putObject(cache, countCacheKey, page.getTotal());
                        }
                        // 这里就是简单的new加返回，那么get(0)能拿到什么？
                        return new PageList(records, page.getTotal());

最终程序以分页失败而告终，这个是一个bug吗？

报错信息

 Consume Time：1 ms 2020-08-30 16:20:54
 Execute SQL：SELECT COUNT(1) FROM sys_user WHERE deleted = 0



org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
### The error may exist in com/ilxqx/nuojiayun/admin/mapper/system/UserMapper.java (best guess)
### The error may involve com.ilxqx.nuojiayun.admin.mapper.system.UserMapper.selectPage_mpCount
### The error occurred while handling results
### SQL: SELECT COUNT(1) FROM sys_user WHERE deleted = 0
### Cause: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0

    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:92)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:440)
    at com.sun.proxy.$Proxy101.selectList(Unknown Source)
    at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:223)
    at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.executeForIPage(MybatisMapperMethod.java:122)
    at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:87)
    at com.baomidou.mybatisplus.core.override.MybatisMapperProxy$PlainMethodInvoker.invoke(MybatisMapperProxy.java:148)
    at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:89)
    at com.sun.proxy.$Proxy102.selectPage(Unknown Source)
    at com.ilxqx.nuojiayun.admin.AdminApplicationTests.contextLoads(AdminApplicationTests.java:31)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:686)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor$$Lambda$131/0000000000000000.apply(Unknown Source)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall$$Lambda$132/0000000000000000.apply(Unknown Source)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$$Lambda$340/0000000000000000.apply(Unknown Source)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:212)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor$$Lambda$1413/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:208)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:137)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:71)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$201/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$200/0000000000000000.invoke(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$199/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService$$Lambda$205/0000000000000000.accept(Unknown Source)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$201/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$200/0000000000000000.invoke(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$199/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService$$Lambda$205/0000000000000000.accept(Unknown Source)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$201/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$200/0000000000000000.invoke(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$$Lambda$199/0000000000000000.execute(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:248)
    at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$5(DefaultLauncher.java:211)
    at org.junit.platform.launcher.core.DefaultLauncher$$Lambda$159/0000000000000000.accept(Unknown Source)
    at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:226)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:199)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:132)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
### The error may exist in com/ilxqx/nuojiayun/admin/mapper/system/UserMapper.java (best guess)
### The error may involve com.ilxqx.nuojiayun.admin.mapper.system.UserMapper.selectPage_mpCount
### The error occurred while handling results
### SQL: SELECT COUNT(1) FROM sys_user WHERE deleted = 0
### Cause: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:149)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:426)
    ... 87 more
Caused by: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
    at java.base/java.util.Objects.checkIndex(Objects.java:372)
    at java.base/java.util.ArrayList.get(ArrayList.java:459)
    at com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor.willDoQuery(PaginationInnerInterceptor.java:137)
    at com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor.intercept(MybatisPlusInterceptor.java:58)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61)
    at com.sun.proxy.$Proxy150.query(Unknown Source)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)
    ... 93 more

Comment From: hbwhypw

我也遇到了！ 出现这个问题的前提是查询的结果空，但要是有任意一条数据，就没有问题。 建议分页查询前，先count一下，若是0直接返回，若是大于0，再执行selectPage