JAVA高级面试进阶训练营视频教程

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1、在pom.xml文件中引入相应依赖

    <!-- mysql依赖 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.42</version>
    </dependency>
    
    <!-- jdbc依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>

2、创建Grade类

public class Grade {

    private int id;
    private String gradeNm;
    private int teacherId;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getGradeNm() {
        return gradeNm;
    }
    public void setGradeNm(String gradeNm) {
        this.gradeNm = gradeNm;
    }
    public int getTeacherId() {
        return teacherId;
    }
    public void setTeacherId(int teacherId) {
        this.teacherId = teacherId;
    }
}

View Code

3、创建GradeDAO

　　在insert方法中获取自增长id，在findByGradeNm和findAll方法中封装返回对象

import java.sql.ResultSet; import java.sql.SQLException; import javax.annotation.Resource; import org.springframework.jdbc.core.BeanPropertyRowMapper; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.core.RowMapper; import org.springframework.stereotype.Repository; import com.wyl.bean.Grade; @Repository public class GradeDAO{ @Resource private JdbcTemplate jdbcTemplate; public Grade findByGradeNm(String gradeNm) { String sql = "select * from Grade where grade_Nm='" + gradeNm + "'"; RowMapper<Grade> rm = new GradeRowMapper(); return jdbcTemplate.queryForObject(sql,rm); }

　　public List<Grade> findAll() {
        String sql = "select * from Grade";
        RowMapper<Grade> rm = new GradeRowMapper();
        return jdbcTemplate.query(sql, rm);
    }
　　/*
     * jdbc默认插入数据库中没有返回集 ,可以对数据进行封装，使其返回插入的对象
     */
    public Grade insertGrade(final Grade grade){
        final String sql = "insert into grade(grade_nm, teacher_id) values(?,?)";
        KeyHolder holder = new GeneratedKeyHolder();
        
        jdbc.update(new PreparedStatementCreator() {
            @Override
            public PreparedStatement createPreparedStatement(Connection connection) throws SQLException {
                // TODO Auto-generated method stub
                PreparedStatement ps = connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
                ps.setString(1, grade.getGradeNm());
                ps.setInt(2, grade.getTeacherId());
                return ps;
            }
        }, holder);
        
        int newGradeId = holder.getKey().intValue();//获得自增长的id
        grade.setId(newGradeId);
        return grade;
    } /*
　　 * 必须自己手动封装Grade类，因为Springboot默认将数据库中的一列封装为一个对象
　　 */ class GradeRowMapper implements RowMapper<Grade>{ @Override public Grade mapRow(ResultSet rs, int rowNum) throws SQLException { // TODO Auto-generated method stub Grade grade = new Grade(); grade.setGradeNm(rs.getString("grade_nm")); grade.setId(rs.getInt("id")); grade.setTeacherId(rs.getInt("teacher_id")); return grade; } } }

4、创建GradeService

import javax.annotation.Resource; import org.springframework.stereotype.Service; import com.wyl.bean.Grade; import com.wyl.dao.GradeDAO; /** * GradeService类，调用gradeDAO中的方法 * */ @Service public class GradeService { @Resource private GradeDAO gradeDAO; public Grade fingByGradeNm(String gradeNm){ return gradeDAO.findByGradeNm(gradeNm); }
　　
　　public List<Grade> fingAll(){
        return gradeDAO.findAll();
    }
　　
　　public Grade insertGrade(Grade grade){
        return gradeDAO.insertGrade(grade);
    } }

5、创建GradeController

import javax.annotation.Resource; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.wyl.bean.Grade; import com.wyl.service.GradeService; @RestController public class JPAController { @Resource private GradeService gradeService; @RequestMapping("/finfByGradeNm") public Grade finfByGradeNm(String gradeNm){ System.out.println("finfByGradeNm"); return gradeService.fingByGradeNm(gradeNm); }

　　@RequestMapping("/findAll")
    public List<Grade> findAll(String gradeNm){
        System.out.println("findAll");
        return gradeService.fingAll();
    }

　　@RequestMapping("/insertGrade")
    public Grade insertGrade(Grade grade){
        System.out.println("insertGrade");
        return gradeService.insertGrade(grade);
    } }

6、测试

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration$LiquibaseConfiguration': Invocation of init method failed; nested exception is java.lang.IllegalStateException: Cannot find changelog location: class path resource [db/changelog/db.changelog-master.yaml] (please add changelog or check your Liquibase configuration)
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:137) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:409) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1620) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at com.wyl.App.main(App.java:16) [classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_60]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_60]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_60]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-1.5.3.RELEASE.jar:1.5.3.RELEASE]
Caused by: java.lang.IllegalStateException: Cannot find changelog location: class path resource [db/changelog/db.changelog-master.yaml] (please add changelog or check your Liquibase configuration)
    at org.springframework.util.Assert.state(Assert.java:70) ~[spring-core-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration$LiquibaseConfiguration.checkChangelogExists(LiquibaseAutoConfiguration.java:92) ~[spring-boot-autoconfigure-1.5.3.RELEASE.jar:1.5.3.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_60]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_60]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_60]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:311) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:134) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
    ... 23 common frames omitted

 

测试出现以上问题是因为liquibase中需要db.changelog-master.yaml文件

解决方法：

　　1、在application.properties中添加如下代码：

liquibase.change-log=classpath:/liquibase/db.changelog.xml

　　2、在src/main/resource包下创建/liquibase/db.changelog.xml目录，并且db.changelog.xml中的内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog/1.9" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog/1.9 http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-1.9.xsd">
    <changeSet id="1" author="jim">

        <createTable tableName="useraccount">
            <column name="userid" type="bigint(20)">
                <constraints primaryKey="true" />
            </column>
            <column name="accountstate" type="varchar(255)" />
            <column name="expiredDate" type="datetime" />
            <column name="username" type="varchar(255)" />
        </createTable>

        <addUniqueConstraint tableName="useraccount" columnNames="username" constraintName="username" />

    </changeSet>

    <changeSet id="2" author="jim">

        <addColumn tableName="useraccount">
            <column name="gender" type="varchar(1)" value="M">
                <constraints nullable="false" />
            </column>
        </addColumn>

    </changeSet>

</databaseChangeLog>   

解决之后的测试结果：

　　

 

　　insert方法返回插入的对象：