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415 lines
15 KiB
415 lines
15 KiB
# Mybatis DyanmicSqlSourcce
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- Author: [HuiFer](https://github.com/huifer)
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- 源码阅读工程: [SourceHot-Mybatis](https://github.com/SourceHot/mybatis-read.git)
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- `org.apache.ibatis.scripting.xmltags.DynamicSqlSource`
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- `org.apache.ibatis.scripting.xmltags.DynamicContext.DynamicContext`
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```XML
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<select id="list" resultType="com.huifer.mybatis.entity.HsSell">
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select * from hs_sell
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<trim prefix="WHERE" prefixOverrides="AND |OR">
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<if test="ID != null">
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and ID = #{ID,jdbcType=INTEGER}
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</if>
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</trim>
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</select>
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```
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```java
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public class MixedSqlNode implements SqlNode {
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private final List<SqlNode> contents;
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public MixedSqlNode(List<SqlNode> contents) {
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this.contents = contents;
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}
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@Override
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public boolean apply(DynamicContext context) {
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// 调用 salNode 对象本身的 apply 方法解析 sql
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contents.forEach(node -> node.apply(context));
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return true;
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}
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}
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```
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- 根据 mapper.xml 文件中的代码流程 需要走
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`org.apache.ibatis.scripting.xmltags.StaticTextSqlNode#apply`
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`org.apache.ibatis.scripting.xmltags.TrimSqlNode#apply`
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`org.apache.ibatis.scripting.xmltags.IfSqlNode#apply`
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```java
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/**
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* @author Clinton Begin
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*/
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public class StaticTextSqlNode implements SqlNode {
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private final String text;
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public StaticTextSqlNode(String text) {
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this.text = text;
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}
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/**
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* 静态文本apply 方法
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* @param context
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* @return
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*/
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@Override
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public boolean apply(DynamicContext context) {
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context.appendSql(text);
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return true;
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}
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}
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```
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- `org.apache.ibatis.scripting.xmltags.DynamicContext#appendSql`
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```java
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public void appendSql(String sql) {
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sqlBuilder.add(sql);
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}
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```
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- 解析`trim`标签
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- 在解析`trim`的时候会往下解析下级标签
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```java
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@Override
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public boolean apply(DynamicContext context) {
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FilteredDynamicContext filteredDynamicContext = new FilteredDynamicContext(context);
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// 解析下级标签的入口
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boolean result = contents.apply(filteredDynamicContext);
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filteredDynamicContext.applyAll();
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return result;
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}
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```
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```java
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@Override
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public boolean apply(DynamicContext context) {
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if (evaluator.evaluateBoolean(test, context.getBindings())) {
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contents.apply(context);
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return true;
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}
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return false;
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}
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```
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- `evaluator.evaluateBoolean(test, context.getBindings())`方法
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```java
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/**
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* @param expression 判断语句,ID != null
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* @param parameterObject 参数列表
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* @return
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*/
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public boolean evaluateBoolean(String expression, Object parameterObject) {
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Object value = OgnlCache.getValue(expression, parameterObject);
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if (value instanceof Boolean) {
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return (Boolean) value;
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}
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if (value instanceof Number) {
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return new BigDecimal(String.valueOf(value)).compareTo(BigDecimal.ZERO) != 0;
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}
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return value != null;
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}
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```
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```java
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/**
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* 取值
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* @param expression 判断语句,ID=NULL
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* @param root 参数列表
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* @return
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*/
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public static Object getValue(String expression, Object root) {
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try {
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Map context = Ognl.createDefaultContext(root, MEMBER_ACCESS, CLASS_RESOLVER, null);
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// 判断是否存在 expression 的判断内容 (判断ID是否存在)
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return Ognl.getValue(parseExpression(expression), context, root);
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} catch (OgnlException e) {
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throw new BuilderException("Error evaluating expression '" + expression + "'. Cause: " + e, e);
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}
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}
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```
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存在返回`true`
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执行完成就得到了一个 sql
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继续执行`org.apache.ibatis.scripting.xmltags.DynamicSqlSource#getBoundSql`方法
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- 发送 sql`org.apache.ibatis.executor.SimpleExecutor#doQuery`
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- 调用链路如下
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- `org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler)`
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- `org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)`
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- `org.apache.ibatis.executor.Executor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)`
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- `org.apache.ibatis.executor.BaseExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)`
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```java
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@SuppressWarnings("unchecked")
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@Override
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public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
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ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
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if (closed) {
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// 判断当前是否关闭
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throw new ExecutorException("Executor was closed.");
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}
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if (queryStack == 0 && ms.isFlushCacheRequired()) {
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// 查询堆栈==0 和 是否需要刷新缓存
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// 清理本地缓存
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clearLocalCache();
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}
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List<E> list;
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try {
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// 堆栈+1,防止重新清理缓存
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queryStack++;
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// 通过 缓存key 在本地缓存中获取
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list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
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if (list != null) {
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// 通过缓存 key 查到后处理 localOutputParameterCache
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handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
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} else {
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// 没有查询到从数据库查询
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list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
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}
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} finally {
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// 堆栈-1
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queryStack--;
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}
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if (queryStack == 0) {
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for (DeferredLoad deferredLoad : deferredLoads) {
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deferredLoad.load();
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}
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// 清空线程安全队列(延迟队列)
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// issue #601
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deferredLoads.clear();
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if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
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// STATEMENT 清空本地缓存
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// issue #482
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clearLocalCache();
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}
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}
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return list;
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}
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```
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- `org.apache.ibatis.executor.BaseExecutor#queryFromDatabase`
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```java
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private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
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List<E> list;
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localCache.putObject(key, EXECUTION_PLACEHOLDER);
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try {
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list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
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} finally {
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localCache.removeObject(key);
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}
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localCache.putObject(key, list);
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if (ms.getStatementType() == StatementType.CALLABLE) {
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localOutputParameterCache.putObject(key, parameter);
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}
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return list;
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}
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```
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- `org.apache.ibatis.executor.BaseExecutor#doQuery`
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- `org.apache.ibatis.executor.SimpleExecutor#doQuery`
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```java
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private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
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Statement stmt;
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// 数据库连接
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Connection connection = getConnection(statementLog);
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// stms 创建
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// org.apache.ibatis.executor.statement.BaseStatementHandler.prepare
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stmt = handler.prepare(connection, transaction.getTimeout());
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// 参数放入
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handler.parameterize(stmt);
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return stmt;
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}
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```
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- `org.apache.ibatis.executor.statement.BaseStatementHandler#prepare`
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- `org.apache.ibatis.executor.statement.PreparedStatementHandler#instantiateStatement`
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```java
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@Override
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public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
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ErrorContext.instance().sql(boundSql.getSql());
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Statement statement = null;
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try {
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statement = instantiateStatement(connection);
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setStatementTimeout(statement, transactionTimeout);
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setFetchSize(statement);
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return statement;
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} catch (SQLException e) {
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closeStatement(statement);
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throw e;
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} catch (Exception e) {
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closeStatement(statement);
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throw new ExecutorException("Error preparing statement. Cause: " + e, e);
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}
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}
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```
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```java
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@Override
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protected Statement instantiateStatement(Connection connection) throws SQLException {
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String sql = boundSql.getSql();
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if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
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String[] keyColumnNames = mappedStatement.getKeyColumns();
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if (keyColumnNames == null) {
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return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
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} else {
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return connection.prepareStatement(sql, keyColumnNames);
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}
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} else if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
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return connection.prepareStatement(sql);
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} else {
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return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
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}
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}
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```
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- 这个方法都去了`java.sql.Connection#prepareStatement(java.lang.String, java.lang.String[])`
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- 接下来需要考虑的问题是如何将`?`换成我们的参数`2`
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- `org.apache.ibatis.executor.statement.StatementHandler#parameterize`
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- `org.apache.ibatis.executor.statement.RoutingStatementHandler#parameterize`
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- `org.apache.ibatis.executor.statement.StatementHandler#parameterize`
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- `org.apache.ibatis.executor.statement.PreparedStatementHandler#parameterize`
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- `org.apache.ibatis.executor.parameter.ParameterHandler`
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- `org.apache.ibatis.scripting.defaults.DefaultParameterHandler#setParameters`
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这样就拿到了`value`的值
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准备工作就绪了发送就可以了
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`doQuery`的工作完成了继续往下走
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```java
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@Override
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public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
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Statement stmt = null;
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try {
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Configuration configuration = ms.getConfiguration();
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StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
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stmt = prepareStatement(handler, ms.getStatementLog());
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return handler.query(stmt, resultHandler);
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} finally {
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closeStatement(stmt);
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}
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}
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```
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- `org.apache.ibatis.executor.statement.RoutingStatementHandler#query`
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- `org.apache.ibatis.executor.statement.PreparedStatementHandler#query`
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- `org.apache.ibatis.executor.resultset.ResultSetHandler#handleResultSets`
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- `org.apache.ibatis.executor.resultset.DefaultResultSetHandler#handleResultSets`
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处理后结果如上
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```java
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/**
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* 处理查询结果
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* @param stmt
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* @return
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* @throws SQLException
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*/
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@Override
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public List<Object> handleResultSets(Statement stmt) throws SQLException {
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ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
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final List<Object> multipleResults = new ArrayList<>();
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int resultSetCount = 0;
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ResultSetWrapper rsw = getFirstResultSet(stmt);
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List<ResultMap> resultMaps = mappedStatement.getResultMaps();
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int resultMapCount = resultMaps.size();
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validateResultMapsCount(rsw, resultMapCount);
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while (rsw != null && resultMapCount > resultSetCount) {
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ResultMap resultMap = resultMaps.get(resultSetCount);
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handleResultSet(rsw, resultMap, multipleResults, null);
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rsw = getNextResultSet(stmt);
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cleanUpAfterHandlingResultSet();
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resultSetCount++;
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}
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String[] resultSets = mappedStatement.getResultSets();
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if (resultSets != null) {
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while (rsw != null && resultSetCount < resultSets.length) {
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ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
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if (parentMapping != null) {
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String nestedResultMapId = parentMapping.getNestedResultMapId();
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ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
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handleResultSet(rsw, resultMap, null, parentMapping);
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}
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rsw = getNextResultSet(stmt);
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cleanUpAfterHandlingResultSet();
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resultSetCount++;
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}
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}
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// 查询结果
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return collapseSingleResultList(multipleResults);
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}
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```
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