一、mybatis一级缓存
spring当中为什么失效？
因为mybatis和spring的集成包当中扩展了一个类SqlSessionTemplate, 这个类在spring容器启动的时候被注入给了MapperStatement, 这个类替代了原来的DefaultSqlSession, SqlSessionTemplate当中的所有查询方法不是直接查询， 而是经过一个代理对象，代理对象增强了查询方法，然后关闭了自己新建的session
MapperMethod == spring中的BD
public class MapperMethod {
private final SqlCommand command;
private final MethodSignature method;
public MapperMethod(Class<?> mapperInterface, Method method, Configuration config) {
this.command = new SqlCommand(config, mapperInterface, method);
this.method = new MethodSignature(config, mapperInterface, method);
}
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
Object param;
switch (this.command.getType()) {
case INSERT:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.insert(this.command.getName(), param));
break;
case UPDATE:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.update(this.command.getName(), param));
break;
case DELETE:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.delete(this.command.getName(), param));
break;
case SELECT:
if (this.method.returnsVoid() && this.method.hasResultHandler()) {
this.executeWithResultHandler(sqlSession, args);
result = null;
} else if (this.method.returnsMany()) {
result = this.executeForMany(sqlSession, args);
} else if (this.method.returnsMap()) {
result = this.executeForMap(sqlSession, args);
} else if (this.method.returnsCursor()) {
result = this.executeForCursor(sqlSession, args);
} else {
param = this.method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(this.command.getName(), param);
if (this.method.returnsOptional() && (result == null || !this.method.getReturnType().equals(result.getClass()))) {
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + this.command.getName());
}
if (result == null && this.method.getReturnType().isPrimitive() && !this.method.returnsVoid()) {
throw new BindingException("Mapper method '" + this.command.getName() + " attempted to return null from a method with a primitive return type (" + this.method.getReturnType() + ").");
} else {
return result;
}
}
private Object rowCountResult(int rowCount) {
Object result;
if (this.method.returnsVoid()) {
result = null;
} else if (!Integer.class.equals(this.method.getReturnType()) && !Integer.TYPE.equals(this.method.getReturnType())) {
if (!Long.class.equals(this.method.getReturnType()) && !Long.TYPE.equals(this.method.getReturnType())) {
if (!Boolean.class.equals(this.method.getReturnType()) && !Boolean.TYPE.equals(this.method.getReturnType())) {
throw new BindingException("Mapper method '" + this.command.getName() + "' has an unsupported return type: " + this.method.getReturnType());
}
result = rowCount > 0;
} else {
result = (long)rowCount;
}
} else {
result = rowCount;
}
return result;
}
private void executeWithResultHandler(SqlSession sqlSession, Object[] args) {
MappedStatement ms = sqlSession.getConfiguration().getMappedStatement(this.command.getName());
if (!StatementType.CALLABLE.equals(ms.getStatementType()) && Void.TYPE.equals(((ResultMap)ms.getResultMaps().get(0)).getType())) {
throw new BindingException("method " + this.command.getName() + " needs either a @ResultMap annotation, a @ResultType annotation, or a resultType attribute in XML so a ResultHandler can be used as a parameter.");
} else {
Object param = this.method.convertArgsToSqlCommandParam(args);
if (this.method.hasRowBounds()) {
RowBounds rowBounds = this.method.extractRowBounds(args);
sqlSession.select(this.command.getName(), param, rowBounds, this.method.extractResultHandler(args));
} else {
sqlSession.select(this.command.getName(), param, this.method.extractResultHandler(args));
}
}
}
private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {
Object param = this.method.convertArgsToSqlCommandParam(args);
List result;
if (this.method.hasRowBounds()) {
RowBounds rowBounds = this.method.extractRowBounds(args);
result = sqlSession.selectList(this.command.getName(), param, rowBounds);
} else {
result = sqlSession.selectList(this.command.getName(), param);
}
if (!this.method.getReturnType().isAssignableFrom(result.getClass())) {
return this.method.getReturnType().isArray() ? this.convertToArray(result) : this.convertToDeclaredCollection(sqlSession.getConfiguration(), result);
} else {
return result;
}
}
private <T> Cursor<T> executeForCursor(SqlSession sqlSession, Object[] args) {
Object param = this.method.convertArgsToSqlCommandParam(args);
Cursor result;
if (this.method.hasRowBounds()) {
RowBounds rowBounds = this.method.extractRowBounds(args);
result = sqlSession.selectCursor(this.command.getName(), param, rowBounds);
} else {
result = sqlSession.selectCursor(this.command.getName(), param);
}
return result;
}
private <E> Object convertToDeclaredCollection(Configuration config, List<E> list) {
Object collection = config.getObjectFactory().create(this.method.getReturnType());
MetaObject metaObject = config.newMetaObject(collection);
metaObject.addAll(list);
return collection;
}
private <E> Object convertToArray(List<E> list) {
Class<?> arrayComponentType = this.method.getReturnType().getComponentType();
Object array = Array.newInstance(arrayComponentType, list.size());
if (!arrayComponentType.isPrimitive()) {
return list.toArray((Object[])((Object[])array));
} else {
for(int i = 0; i < list.size(); ++i) {
Array.set(array, i, list.get(i));
}
return array;
}
}
private <K, V> Map<K, V> executeForMap(SqlSession sqlSession, Object[] args) {
Object param = this.method.convertArgsToSqlCommandParam(args);
Map result;
if (this.method.hasRowBounds()) {
RowBounds rowBounds = this.method.extractRowBounds(args);
result = sqlSession.selectMap(this.command.getName(), param, this.method.getMapKey(), rowBounds);
} else {
result = sqlSession.selectMap(this.command.getName(), param, this.method.getMapKey());
}
return result;
}
public static class MethodSignature {
private final boolean returnsMany;
private final boolean returnsMap;
private final boolean returnsVoid;
private final boolean returnsCursor;
private final boolean returnsOptional;
private final Class<?> returnType;
private final String mapKey;
private final Integer resultHandlerIndex;
private final Integer rowBoundsIndex;
private final ParamNameResolver paramNameResolver;
public MethodSignature(Configuration configuration, Class<?> mapperInterface, Method method) {
Type resolvedReturnType = TypeParameterResolver.resolveReturnType(method, mapperInterface);
if (resolvedReturnType instanceof Class) {
this.returnType = (Class)resolvedReturnType;
} else if (resolvedReturnType instanceof ParameterizedType) {
this.returnType = (Class)((ParameterizedType)resolvedReturnType).getRawType();
} else {
this.returnType = method.getReturnType();
}
this.returnsVoid = Void.TYPE.equals(this.returnType);
this.returnsMany = configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray();
this.returnsCursor = Cursor.class.equals(this.returnType);
this.returnsOptional = Optional.class.equals(this.returnType);
this.mapKey = this.getMapKey(method);
this.returnsMap = this.mapKey != null;
this.rowBoundsIndex = this.getUniqueParamIndex(method, RowBounds.class);
this.resultHandlerIndex = this.getUniqueParamIndex(method, ResultHandler.class);
this.paramNameResolver = new ParamNameResolver(configuration, method);
}
public Object convertArgsToSqlCommandParam(Object[] args) {
return this.paramNameResolver.getNamedParams(args);
}
public boolean hasRowBounds() {
return this.rowBoundsIndex != null;
}
public RowBounds extractRowBounds(Object[] args) {
return this.hasRowBounds() ? (RowBounds)args[this.rowBoundsIndex] : null;
}
public boolean hasResultHandler() {
return this.resultHandlerIndex != null;
}
public ResultHandler extractResultHandler(Object[] args) {
return this.hasResultHandler() ? (ResultHandler)args[this.resultHandlerIndex] : null;
}
public Class<?> getReturnType() {
return this.returnType;
}
public boolean returnsMany() {
return this.returnsMany;
}
public boolean returnsMap() {
return this.returnsMap;
}
public boolean returnsVoid() {
return this.returnsVoid;
}
public boolean returnsCursor() {
return this.returnsCursor;
}
public boolean returnsOptional() {
return this.returnsOptional;
}
private Integer getUniqueParamIndex(Method method, Class<?> paramType) {
Integer index = null;
Class<?>[] argTypes = method.getParameterTypes();
for(int i = 0; i < argTypes.length; ++i) {
if (paramType.isAssignableFrom(argTypes[i])) {
if (index != null) {
throw new BindingException(method.getName() + " cannot have multiple " + paramType.getSimpleName() + " parameters");
}
index = i;
}
}
return index;
}
public String getMapKey() {
return this.mapKey;
}
private String getMapKey(Method method) {
String mapKey = null;
if (Map.class.isAssignableFrom(method.getReturnType())) {
MapKey mapKeyAnnotation = (MapKey)method.getAnnotation(MapKey.class);
if (mapKeyAnnotation != null) {
mapKey = mapKeyAnnotation.value();
}
}
return mapKey;
}
}
public static class SqlCommand {
private final String name;
private final SqlCommandType type;
public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method method) {
String methodName = method.getName();
Class<?> declaringClass = method.getDeclaringClass();
MappedStatement ms = this.resolveMappedStatement(mapperInterface, methodName, declaringClass, configuration);
if (ms == null) {
if (method.getAnnotation(Flush.class) == null) {
throw new BindingException("Invalid bound statement (not found): " + mapperInterface.getName() + "." + methodName);
}
this.name = null;
this.type = SqlCommandType.FLUSH;
} else {
this.name = ms.getId();
this.type = ms.getSqlCommandType();
if (this.type == SqlCommandType.UNKNOWN) {
throw new BindingException("Unknown execution method for: " + this.name);
}
}
}
public String getName() {
return this.name;
}
public SqlCommandType getType() {
return this.type;
}
private MappedStatement resolveMappedStatement(Class<?> mapperInterface, String methodName, Class<?> declaringClass, Configuration configuration) {
String statementId = mapperInterface.getName() + "." + methodName;
if (configuration.hasStatement(statementId)) {
return configuration.getMappedStatement(statementId);
} else if (mapperInterface.equals(declaringClass)) {
return null;
} else {
Class[] var6 = mapperInterface.getInterfaces();
int var7 = var6.length;
for(int var8 = 0; var8 < var7; ++var8) {
Class<?> superInterface = var6[var8];
if (declaringClass.isAssignableFrom(superInterface)) {
MappedStatement ms = this.resolveMappedStatement(superInterface, methodName, declaringClass, configuration);
if (ms != null) {
return ms;
}
}
}
return null;
}
}
}
public static class ParamMap<V> extends HashMap<String, V> {
private static final long serialVersionUID = -2212268410512043556L;
public ParamMap() {
}
public V get(Object key) {
if (!super.containsKey(key)) {
throw new BindingException("Parameter '" + key + "' not found. Available parameters are " + this.keySet());
} else {
return super.get(key);
}
}
}
}DefaultSqlSession === sqlSessionProxy
SqlSessionTemplate 里面的内部类 SqlSessionInterceptor
mybatis单独执行和mybatis-spring执行的区别：
Sqlsession 接口的实现类：
DefaultSqlSession(mybatis): —- > execute
MappedStatement 包含了select/update/delete/add 的所有信息
SqlSessionTemplate(mybatis + spring):
sqlSessionProxy —- > proxy —-> execute
SqlSessionTemplate 实例化：
create UserMapper — > MappedFactoryBean —- > setFactoryBean
Mybatis的执行器：
- SimpleExecutor:普通的执行器，默认
- ReuseExecutor: 执行器会重用预处理的语句(PreparedStatement)
- BatchExecutor: 执行器不仅重用语句还会执行批量更新（适用于增删改操作）
SimpleExecutor ：
ReuseExecutor ：
BatchExecutor ：
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