浅谈MyBatis Plus主键设置策略
作者：qinghuazs
本文主要介绍了MyBatis Plus主键设置策略，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧
根据一次插入失败报错来了解下MyBatis Plus主键设置策略
今天学习使用MyBatis Plus，发现使用代码生成器生成对应的实体类、Service和Mapper后，在保存数据时报错
com.baomidou.mybatisplus.exceptions.MybatisPlusException: java.lang.reflect.InvocationTargetException
at com.baomidou.mybatisplus.MybatisSqlSessionTemplate$SqlSessionInterceptor.invoke(MybatisSqlSessionTemplate.java:405)
at com.sun.proxy.$Proxy70.insert(Unknown Source)
at com.baomidou.mybatisplus.MybatisSqlSessionTemplate.insert(MybatisSqlSessionTemplate.java:243)
at com.baomidou.mybatisplus.activerecord.Model.insert(Model.java:56)
at com.lemon.rabbit.common.base.city.CityInitial.printInfo(CityInitial.java:112)
at com.lemon.rabbit.common.base.city.CityInitial.parseNextLevel(CityInitial.java:87)
at com.lemon.rabbit.common.base.city.CityInitial.test(CityInitial.java:59)
at com.lemon.rabbit.RabbitApplicationTests.contextLoads(RabbitApplicationTests.java:19)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.baomidou.mybatisplus.MybatisSqlSessionTemplate$SqlSessionInterceptor.invoke(MybatisSqlSessionTemplate.java:401)
... 37 more
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error updating database. Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.lemon.rabbit.model.City' with value '1017367047558582273' Cause: java.lang.IllegalArgumentException: argument type mismatch
### Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.lemon.rabbit.model.City' with value '1017367047558582273' Cause: java.lang.IllegalArgumentException: argument type mismatch
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:200)
at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:185)
... 42 more
Caused by: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.lemon.rabbit.model.City' with value '1017367047558582273' Cause: java.lang.IllegalArgumentException: argument type mismatch
at org.apache.ibatis.reflection.wrapper.BeanWrapper.setBeanProperty(BeanWrapper.java:185)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.set(BeanWrapper.java:59)
at org.apache.ibatis.reflection.MetaObject.setValue(MetaObject.java:140)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.populateKeys(MybatisDefaultParameterHandler.java:217)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.processBatch(MybatisDefaultParameterHandler.java:156)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.<init>(MybatisDefaultParameterHandler.java:71)
at com.baomidou.mybatisplus.MybatisXMLLanguageDriver.createParameterHandler(MybatisXMLLanguageDriver.java:37)
at org.apache.ibatis.session.Configuration.newParameterHandler(Configuration.java:545)
at org.apache.ibatis.executor.statement.BaseStatementHandler.<init>(BaseStatementHandler.java:69)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.<init>(PreparedStatementHandler.java:40)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.<init>(RoutingStatementHandler.java:46)
at org.apache.ibatis.session.Configuration.newStatementHandler(Configuration.java:558)
at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:48)
at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)
... 43 more
Caused by: java.lang.IllegalArgumentException: argument type mismatch
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.ibatis.reflection.invoker.MethodInvoker.invoke(MethodInvoker.java:41)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.setBeanProperty(BeanWrapper.java:180)
... 58 more实体类City的主键是Integer类型的，在进行insert操作时，MyBatis Plus自动生成了一个Long类型的主键id，导致参数类型不匹配，出现上述错误
经过查看日志和调试发现，MyBatis最终调用BeanWrapper的setBeanProperty方法，通过反射执行最终的插入操作（增删改查应该都是通过此处的反射，不过暂时只调试了insert方法）
private void setBeanProperty(PropertyTokenizer prop, Object object, Object value) {
try {
Invoker method = metaClass.getSetInvoker(prop.getName());
Object[] params = {value};
try {
method.invoke(object, params);
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
} catch (Throwable t) {
throw new ReflectionException("Could not set property '" + prop.getName() + "' of '" + object.getClass() + "' with value '" + value + "' Cause: " + t.toString(), t);
}
}
此处传入的object即为我们想要保存到数据库的实体信息（不带ID信息），value为主键信息，此时主键值已经是一个Long类型的值，我们接着向上看value是哪里传过来的
setBeanProperty是一个私有方法，在本类调用，查询看到set(PropertyTokenizer prop, Object value)方法调用了它
@Override
public void set(PropertyTokenizer prop, Object value) {
if (prop.getIndex() != null) {
Object collection = resolveCollection(prop, object);
setCollectionValue(prop, collection, value);
} else {
setBeanProperty(prop, object, value);
}
}set方法中的value也是其他地方传入的
Caused by: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.lemon.rabbit.model.City' with value '1017367047558582273' Cause: java.lang.IllegalArgumentException: argument type mismatch
at org.apache.ibatis.reflection.wrapper.BeanWrapper.setBeanProperty(BeanWrapper.java:185)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.set(BeanWrapper.java:59)
at org.apache.ibatis.reflection.MetaObject.setValue(MetaObject.java:140)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.populateKeys(MybatisDefaultParameterHandler.java:217)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.processBatch(MybatisDefaultParameterHandler.java:156)
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.<init>(MybatisDefaultParameterHandler.java:71)
at com.baomidou.mybatisplus.MybatisXMLLanguageDriver.createParameterHandler(MybatisXMLLanguageDriver.java:37)
at org.apache.ibatis.session.Configuration.newParameterHandler(Configuration.java:545)
at org.apache.ibatis.executor.statement.BaseStatementHandler.<init>(BaseStatementHandler.java:69)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.<init>(PreparedStatementHandler.java:40)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.<init>(RoutingStatementHandler.java:46)
at org.apache.ibatis.session.Configuration.newStatementHandler(Configuration.java:558)
at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:48)
at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)
... 43 more
查看报错日志可以看到，BeanWrapper的上一层是MetaObject，我们找到MetaObject，看到在getValue方法中调用了BeanWrapper的set方法(BeanWrapper实现了ObjectWrapper)
public void setValue(String name, Object value) {
PropertyTokenizer prop = new PropertyTokenizer(name);
if (prop.hasNext()) {
MetaObject metaValue = metaObjectForProperty(prop.getIndexedName());
if (metaValue == SystemMetaObject.NULL_META_OBJECT) {
if (value == null && prop.getChildren() != null) {
// don't instantiate child path if value is null
return;
} else {
metaValue = objectWrapper.instantiatePropertyValue(name, prop, objectFactory);
}
}
metaValue.setValue(prop.getChildren(), value);
} else {
objectWrapper.set(prop, value);
}
}MetaObject中的主键值也是上层调用传入的，继续根据错误日志向上看：MybatisDefaultParameterHandler
/**
* <p>
* 自定义元对象填充控制器
* </p>
*
* @param metaObjectHandler 元数据填充处理器
* @param tableInfo 数据库表反射信息
* @param ms MappedStatement
* @param parameterObject 插入数据库对象
* @return Object
*/
protected static Object populateKeys(MetaObjectHandler metaObjectHandler, TableInfo tableInfo,
MappedStatement ms, Object parameterObject) {
if (null == tableInfo || StringUtils.isEmpty(tableInfo.getKeyProperty()) || null == tableInfo.getIdType()) {
/* 不处理 */
return parameterObject;
}
/* 自定义元对象填充控制器 */
MetaObject metaObject = ms.getConfiguration().newMetaObject(parameterObject);
if (ms.getSqlCommandType() == SqlCommandType.INSERT) {
if (tableInfo.getIdType().getKey() >= 2) {
Object idValue = metaObject.getValue(tableInfo.getKeyProperty());
/* 自定义 ID */
if (StringUtils.checkValNull(idValue)) {
if (tableInfo.getIdType() == IdType.ID_WORKER) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getId());
} else if (tableInfo.getIdType() == IdType.ID_WORKER_STR) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getIdStr());
} else if (tableInfo.getIdType() == IdType.UUID) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.get32UUID());
}
}
}
// 插入填充
if (metaObjectHandler.openInsertFill()) {
metaObjectHandler.insertFill(metaObject);
}
} else if (ms.getSqlCommandType() == SqlCommandType.UPDATE && metaObjectHandler.openUpdateFill()) {
// 更新填充
metaObjectHandler.updateFill(metaObject);
}
return metaObject.getOriginalObject();
}在populateKeys方法中调用了metaObject.setValue()
if (StringUtils.checkValNull(idValue)) {
if (tableInfo.getIdType() == IdType.ID_WORKER) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getId());
} else if (tableInfo.getIdType() == IdType.ID_WORKER_STR) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getIdStr());
} else if (tableInfo.getIdType() == IdType.UUID) {
metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.get32UUID());
}
}可以看到，此处根据IdType生成不同类型的主键id，IdType是一个枚举类，定义了生成ID的类型
- AUTO 数据库ID自增
- INPUT 用户输入ID
- ID_WORKER 全局唯一ID，Long类型的主键
- ID_WORKER_STR 字符串全局唯一ID
- UUID 全局唯一ID，UUID类型的主键
- NONE 该类型为未设置主键类型
当IdType的类型为ID_WORKER、ID_WORKER_STR或者UUID时，主键由MyBatis Plus的IdWorker类生成
ID_WORKER
调用IdWorker的getId()方法，生成一个与时间相关的主键id
public static long getId() {
return worker.nextId();
}IdWorker的getId()方法引用了Sequence的nextId()方法
public synchronized long nextId() {
long timestamp = timeGen();
if (timestamp < lastTimestamp) {//闰秒
long offset = lastTimestamp - timestamp;
if (offset <= 5) {
try {
wait(offset << 1);
timestamp = timeGen();
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
} catch (Exception e) {
throw new RuntimeException(e);
}
} else {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
}
if (lastTimestamp == timestamp) {
// 相同毫秒内，序列号自增
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
// 同一毫秒的序列数已经达到最大
timestamp = tilNextMillis(lastTimestamp);
}
} else {
// 不同毫秒内，序列号置为 1 - 3 随机数
sequence = ThreadLocalRandom.current().nextLong(1, 3);
}
lastTimestamp = timestamp;
return ((timestamp - twepoch) << timestampLeftShift) // 时间戳部分
| (datacenterId << datacenterIdShift) // 数据中心部分
| (workerId << workerIdShift) // 机器标识部分
| sequence; // 序列号部分
}
ID_WORKER_STR
将worker.nextId()的返回值转化为字符串，和getId()方法相似
public static String getIdStr() {
return String.valueOf(worker.nextId());
}UUID
去除中划线的UUID字符串
public static synchronized String get32UUID() {
return UUID.randomUUID().toString().replace("-", "");
}此时，已经基本可以确认，问题出在IdType的配置上，那么这个IdType从哪里获取的呢？TableInfo中获取的！
TableInfo是数据库表反射信息实体类，此处由其他方法传入的，查看日志：
at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.populateKeys(MybatisDefaultParameterHandler.java:217) at com.baomidou.mybatisplus.MybatisDefaultParameterHandler.processBatch(MybatisDefaultParameterHandler.java:156)
通过日志可以看出，populateKeys()方法是在processBatch()方法中调用的，找到该方法
/**
* <p>
* 批量（填充主键 ID）
* </p>
*
* @param ms
* @param parameterObject 插入数据库对象
* @return
*/
protected static Object processBatch(MappedStatement ms, Object parameterObject) {
//检查parameterObject
if (null == parameterObject) {
return null;
}
boolean isFill = false;
// 全局配置是否配置填充器
MetaObjectHandler metaObjectHandler = GlobalConfigUtils.getMetaObjectHandler(ms.getConfiguration());
/* 只处理插入或更新操作 */
if (ms.getSqlCommandType() == SqlCommandType.INSERT) {
isFill = true;
} else if (ms.getSqlCommandType() == SqlCommandType.UPDATE
&& metaObjectHandler.openUpdateFill()) {
isFill = true;
}
if (isFill) {
Collection<Object> parameters = getParameters(parameterObject);
if (null != parameters) {
List<Object> objList = new ArrayList<>();
for (Object parameter : parameters) {
TableInfo tableInfo = TableInfoHelper.getTableInfo(parameter.getClass());
if (null != tableInfo) {
objList.add(populateKeys(metaObjectHandler, tableInfo, ms, parameter));
} else {
/*
* 非表映射类不处理
*/
objList.add(parameter);
}
}
return objList;
} else {
TableInfo tableInfo = null;
if (parameterObject instanceof Map) {
Map map = (Map) parameterObject;
if (map.containsKey("et")) {
Object et = map.get("et");
if (et != null) {
if (et instanceof Map) {
Map realEtMap = (Map) et;
if (realEtMap.containsKey("MP_OPTLOCK_ET_ORIGINAL")) {//refer to OptimisticLockerInterceptor.MP_OPTLOCK_ET_ORIGINAL
tableInfo = TableInfoHelper.getTableInfo(realEtMap.get("MP_OPTLOCK_ET_ORIGINAL").getClass());
}
} else {
tableInfo = TableInfoHelper.getTableInfo(et.getClass());
}
}
}
} else {
tableInfo = TableInfoHelper.getTableInfo(parameterObject.getClass());
}
return populateKeys(metaObjectHandler, tableInfo, ms, parameterObject);
}
}
return parameterObject;
}
下面对TableInfo生成的这段代码做个说明
TableInfo tableInfo = null;
if (parameterObject instanceof Map) {
Map map = (Map) parameterObject;
if (map.containsKey("et")) {
Object et = map.get("et");
if (et != null) {
if (et instanceof Map) {
Map realEtMap = (Map) et;
if (realEtMap.containsKey("MP_OPTLOCK_ET_ORIGINAL")) {//refer to OptimisticLockerInterceptor.MP_OPTLOCK_ET_ORIGINAL
tableInfo = TableInfoHelper.getTableInfo(realEtMap.get("MP_OPTLOCK_ET_ORIGINAL").getClass());
}
} else {
tableInfo = TableInfoHelper.getTableInfo(et.getClass());
}
}
}
} else {
tableInfo = TableInfoHelper.getTableInfo(parameterObject.getClass());
}parameterObject：要保存到数据库中的实体类信息
我在保存数据时，参数形式并不是Map类型的，所以直接跳转到else中
tableInfo = TableInfoHelper.getTableInfo(parameterObject.getClass());
根据保存的实体类的类型去获取数据库表反射信息
我们看下getTableInfo()方法的实现
public static TableInfo getTableInfo(Class<?> clazz) {
return tableInfoCache.get(ClassUtils.getUserClass(clazz).getName());
}从tableInfoCache中获取指定类型的数据库反射信息。tableInfoCache是一个线程安全的私有静态Map，主要用于存放类型和数据库表的映射关系。断点调试到此处，看下tableInfoCache的内容
可以看到，idType的值为ID_WORKER，即生成一个与时间相关的Long类型的id。在放入到tableInfoCache的时候就已经指定了idType的值。
查看TableInfoHelper的源码可以得知，initTableInfo()方法负责initTableInfo的初始化
public synchronized static TableInfo initTableInfo(MapperBuilderAssistant builderAssistant, Class<?> clazz) {
//检测是否已存在
TableInfo tableInfo = tableInfoCache.get(clazz.getName());
if (StringUtils.checkValNotNull(tableInfo)) {
if (StringUtils.checkValNotNull(builderAssistant)) {
tableInfo.setConfigMark(builderAssistant.getConfiguration());
}
return tableInfo;
}
tableInfo = new TableInfo();
GlobalConfiguration globalConfig;
if (null != builderAssistant) {
tableInfo.setCurrentNamespace(builderAssistant.getCurrentNamespace());
tableInfo.setConfigMark(builderAssistant.getConfiguration());
//获取全局配置，其中包括了idType
globalConfig = GlobalConfigUtils.getGlobalConfig(builderAssistant.getConfiguration());
} else {
// 兼容测试场景
globalConfig = GlobalConfigUtils.DEFAULT;
}
/* 表名 */
TableName table = clazz.getAnnotation(TableName.class);
String tableName = clazz.getSimpleName();
if (table != null && StringUtils.isNotEmpty(table.value())) {
tableName = table.value();
} else {
// 开启字段下划线申明
if (globalConfig.isDbColumnUnderline()) {
tableName = StringUtils.camelToUnderline(tableName);
}
// 大写命名判断
if (globalConfig.isCapitalMode()) {
tableName = tableName.toUpperCase();
} else {
// 首字母小写
tableName = StringUtils.firstToLowerCase(tableName);
}
// 存在表前缀
if (null != globalConfig.getTablePrefix()) {
tableName = globalConfig.getTablePrefix() + tableName;
}
}
tableInfo.setTableName(tableName);
// 开启了自定义 KEY 生成器
if (null != globalConfig.getKeyGenerator()) {
tableInfo.setKeySequence(clazz.getAnnotation(KeySequence.class));
}
/* 表结果集映射 */
if (table != null && StringUtils.isNotEmpty(table.resultMap())) {
tableInfo.setResultMap(table.resultMap());
}
List<TableFieldInfo> fieldList = new ArrayList<>();
List<Field> list = getAllFields(clazz);
// 标记是否读取到主键
boolean isReadPK = false;
boolean existTableId = existTableId(list);
for (Field field : list) {
/*
* 主键ID 初始化
*/
if (!isReadPK) {
if (existTableId) {
isReadPK = initTableId(globalConfig, tableInfo, field, clazz);
} else {
isReadPK = initFieldId(globalConfig, tableInfo, field, clazz);
}
if (isReadPK) {
continue;
}
}
/*
* 字段初始化
*/
if (initTableField(globalConfig, tableInfo, fieldList, field, clazz)) {
continue;
}
/*
* 字段, 使用 camelToUnderline 转换驼峰写法为下划线分割法, 如果已指定 TableField , 便不会执行这里
*/
fieldList.add(new TableFieldInfo(globalConfig, tableInfo, field));
}
/* 字段列表 */
tableInfo.setFieldList(globalConfig, fieldList);
/*
* 未发现主键注解，提示警告信息
*/
if (StringUtils.isEmpty(tableInfo.getKeyColumn())) {
logger.warn(String.format("Warn: Could not find @TableId in Class: %s.", clazz.getName()));
}
/*
* 注入
*/
tableInfoCache.put(clazz.getName(), tableInfo);
return tableInfo;
}在existTableId方法中判断主键注解@TableId是否存在
/**
* <p>
* 判断主键注解是否存在
* </p>
*
* @param list 字段列表
* @return
*/
public static boolean existTableId(List<Field> list) {
boolean exist = false;
for (Field field : list) {
TableId tableId = field.getAnnotation(TableId.class);
if (tableId != null) {
exist = true;
break;
}
}
return exist;
}当不存在主键注解时，会调用initFieldId()方法对主键属性进行初始化
private static boolean initFieldId(GlobalConfiguration globalConfig, TableInfo tableInfo, Field field, Class<?> clazz) {
String column = field.getName();
if (globalConfig.isCapitalMode()) {
column = column.toUpperCase();
}
if (DEFAULT_ID_NAME.equalsIgnoreCase(column)) {
if (StringUtils.isEmpty(tableInfo.getKeyColumn())) {
tableInfo.setIdType(globalConfig.getIdType());
tableInfo.setKeyColumn(column);
tableInfo.setKeyProperty(field.getName());
return true;
} else {
throwExceptionId(clazz);
}
}
return false;
}至此， 我们基本可以判断是因为在实体类City中id属性没有加@TableId注解，我们看下TableId的源码
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface TableId {
/**
* <p>
* 字段值（驼峰命名方式，该值可无）
* </p>
*/
String value() default "";
/**
* <p>
* 主键ID
* </p>
* {@link IdType}
*/
IdType type() default IdType.NONE;
}TableId的类型通过type来指定，默认是IdType.NONE（该类型为未设置主键类型），City表是通过数据库的自增序列实现的，所以设置为AUTO
@TableId(type = IdType.AUTO) private Integer id;
然后测试，程序正常运行，保存数据成功。
扩展
对于tableInfo默认的idType值配置，可以看出用的是全局配置的idType，全局配置的值是在initTableInfo()方法中获取的，有兴趣的话可以去看看全局配置的实现，此处暂不深入了
GlobalConfiguration globalConfig;
if (null != builderAssistant) {
tableInfo.setCurrentNamespace(builderAssistant.getCurrentNamespace());
tableInfo.setConfigMark(builderAssistant.getConfiguration());
globalConfig = GlobalConfigUtils.getGlobalConfig(builderAssistant.getConfiguration());
} else {
// 兼容测试场景
globalConfig = GlobalConfigUtils.DEFAULT;
}到此这篇关于浅谈MyBatis Plus主键设置策略的文章就介绍到这了,更多相关MyBatis Plus主键设置内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！